JP6834701B2 - Image processing equipment and computer programs - Google Patents

Description

The present specification relates to a technique for detecting an edge in an image.

Conventionally, various image processings have been proposed. For example, a technique has been proposed in which an image is classified into characters and halftone dots by extracting character edges using a differential filter or the like, integrating the amount of isolation, and extracting halftone dots for printing. Further, a technique has been proposed in which the character area in the image and the halftone dot area are distinguished and the characters in the halftone dot area are also determined.

JP-A-2007-31136

By the way, the characters in the image can be expressed in various forms. For example, characters may be expressed in dark colors in a light-colored background. On the contrary, characters may be expressed in light colors in a dark background. It has not been easy to identify the edges of characters that can be represented in such various forms.

The present specification discloses a technique capable of identifying the edges of characters that can be represented in various forms.

The present specification discloses, for example, the following application examples.

[Application Example 1] An image processing apparatus that uses an image data acquisition unit that acquires first image data indicating a first image and the first image data to provide a first image in the first image. It is a first determination unit that determines whether or not a plurality of pixels including one attention pixel satisfy the determination condition of a specific type, and the determination condition of the specific type is that the first attention pixel is less than the reference. The first type of condition indicating that a plurality of pixels having the same brightness are in a continuous low brightness region, and the first attention pixel is a high brightness in which a plurality of pixels having a brightness equal to or higher than a reference are continuous. A second image showing a second image using the first determination unit and the first image data, which is one of the second type conditions indicating that the data is within the region. An image data generation unit that generates data, the second image data includes a plurality of corresponding values corresponding to the values of a plurality of pixels included in the first image data, and the plurality of corresponding values. Each of the corresponding values is a value obtained by reversing the value of the corresponding pixel of the first image data. Using the image data generation unit and the second image data, the second image in the second image is used. The second determination unit that determines whether or not the plurality of pixels including the second attention pixel satisfy the determination condition of the specific type, which is one of the above conditions, and the target image data based on the first image data. On the other hand, it is a smoothing unit that generates smoothing data by executing a smoothing process for smoothing the target image indicated by the target image data, and M pieces (M is 2 or more) in the target image. among the pixels of the integer), the a plurality of pixels of a particular species of determination satisfies said first image, and a plurality of pixels of the particular species of determination satisfies said second image, the (the N1 integer less than M) N1 pieces corresponding to at least one without smoothing the pixels, corresponding to the plurality of pixels within said particular type first which does not satisfy the determination condition of the image, and the The smoothing data is generated by smoothing N2 pixels (N2 is an integer satisfying N1 + N2 = M) corresponding to a plurality of pixels in the second image that do not satisfy a specific type of determination condition. An image processing apparatus comprising the smoothing unit and an edge specifying unit for specifying a plurality of edge pixels indicating edges using the smoothing data.

According to this configuration, it is determined whether or not the determination condition of a specific type is satisfied by using the first image data. Further, it is determined whether or not the determination condition of a specific type is satisfied by using the second image data including the corresponding value obtained by reversing the value of the corresponding pixel of the first image data. As a result, it is possible to judge both the low-luminance region and the high-luminance region by using a specific kind of judgment condition. Then, a plurality of pixels in a particular species determination satisfies the first image, and a plurality of pixels in a particular species determination satisfies the second image, N1 pieces corresponding to at least one of (N1 Is an integer less than M) The smoothed data is generated so that the pixels are not smoothed. Therefore, when identifying edge pixels using smoothed data, pixels representing the edges of characters represented by bright colors in a relatively low-brightness (ie, dark) background and relatively high-brightness (ie) pixels. That is, both pixels representing the edges of characters represented by dark colors in the (bright) background can be appropriately identified.
[Application example 2]
The image processing apparatus according to Application Example 1.
The first determination unit and the second determination unit are filters for detecting pixels representing lines, respectively, and are specified by using a plurality of filters associated with lines having different thicknesses. An image processing device that determines whether or not a species determination condition is met.
[Application example 3]
The image processing apparatus according to Application Example 2.
The first determination unit is a filter for detecting pixels representing lines, and is at least one of P filters (P is an integer of 1 or more) associated with lines having different thicknesses. Is used to determine whether or not the above-mentioned specific type of determination condition is satisfied.
The second determination unit is a filter for detecting pixels representing lines, and has Q pieces (Q is 1 or more and an integer different from P) associated with lines having different thicknesses. At least one of the filters is used to determine whether or not the particular type of determination condition is met.
Image processing device.
[Application example 4]
The image processing apparatus according to Application Example 3.
The specific type of condition is the first type of condition indicating that the first pixel of interest is in a continuous low-luminance region of a plurality of pixels having a brightness less than the reference.
P> Q,
Image processing device.
[Application example 5]
The image processing apparatus according to Application Example 4.
The width of the thinnest line among the P-type lines associated with the P filters that can be used by the first determination unit is the Q associated with the Q filters that can be used by the second determination unit. Thinner than the width of the thinnest of the types of lines,
Image processing device.
[Application example 6]
The image processing apparatus according to Application Example 5.
An output data generation unit that generates output data, which is image data for printing, by performing image processing using the plurality of edge pixels on the input image data.
A supply unit that supplies the output data to a print execution unit that prints an image using a color material, and a supply unit.
With
The first image data is data based on the input image data, and is
The width of the thinnest line among the Q type lines associated with the Q filters that can be used by the second determination unit is determined in advance based on the bleeding characteristics of the color material used by the print execution unit. Has been,
Image processing device.

The techniques disclosed in the present specification can be realized in various aspects, for example, an image processing method and an image processing device, a computer program for realizing the functions of those methods or devices, and a computer thereof. It can be realized in the form of a recording medium on which the program is recorded (for example, a recording medium that is not temporary).

The block diagram which shows the structure of the multifunction device 100. FIG. 3 is a block configuration diagram of the area separation processing unit 103 in the embodiment. The block diagram which shows the structure of the character determination part 1003. The figure for demonstrating the processing of a character determination part. The figure which shows the signal of each process of a character determination part. Explanatory drawing of the table. The block configuration diagram of the halftone dot determination unit 1004. The figure for demonstrating the processing of the halftone dot determination part. The first figure which shows an example of pattern matching. The figure which shows an example of the result of matching with the inner edge signal and determination pattern 1710. The explanatory view of the processing by the OR processing unit 1207. The block diagram which shows the structure of the integration processing unit 1209 and the threshold value determination unit 1211. The figure which shows an example of the processing of the threshold value determination unit 1211 and the comprehensive determination unit 1213. The figure which shows an example of the processing of the threshold value determination unit 1211 and the comprehensive determination unit 1213. The figure which shows an example of the processing of the threshold value determination unit 1211 and the comprehensive determination unit 1213. The block diagram which shows the structure of the character determination part 1005 in a halftone dot. The block diagram which shows the structure of the adaptive smoothing processing part 2401. Explanatory drawing of line pattern. The figure which shows the example of the determination using the line pattern of FIG. 18 (A). It is a figure which shows the example of the determination using the line pattern of FIGS. 18B to 18D. The figure which shows the example of the determination using the line pattern of FIG. 18 (A). FIG. 6 is a diagram showing an example of determination using the line patterns of FIGS. 18 (B) to 18 (D). Explanatory drawing which shows an example of the frequency characteristic of smoothing by an adaptive smoothing processing part. The figure which shows the example of the halftone dot character determination by the halftone dot character determination unit 1005. The figure which shows the example of the halftone dot character determination by the halftone dot character determination unit 1005. The block diagram which shows the structure of the output processing part 110. FIG. 5 is a flowchart showing another embodiment of the process of detecting the pixels of the first type specific region and the pixels of the second type specific region. Explanatory drawing which shows an example of a plurality of filters. Explanatory drawing of the process which determines the initial value Wdiw for a bright line. The block diagram which shows the structure of the area separation processing part 103B of a modification.

A. First Example:
A-1. Configuration of Multifunction Device 100 Next, an embodiment will be described based on an embodiment. FIG. 1 is a block diagram showing a configuration of a multifunction device 100 as an image processing device of an embodiment.

The multifunction device 100 includes a control unit 120, a reading execution unit 130, a printing execution unit 140, a communication interface (communication IF) 150, a display unit such as a liquid crystal display (not shown), and an operation unit including a touch panel and buttons (not shown). And have.

The control unit 120 includes a main processor 101, a plurality of image processing units 102 to 110, a plurality of volatile memories 111 to 116 such as a DRAM, and a non-volatile memory 117 such as a flash memory.

The main processor 101 controls the entire composite machine 100 including the read execution unit 130, the print execution unit 140, and the image processing units 102 to 110 by executing the computer program PG stored in the non-volatile memory 117. It is a CPU.

The plurality of image processing units 102 to 110 are hardware circuits such as an ASIC that operate under the control of the main processor 101. The volatile memories 111 to 116 are memories used by the main processor 101 and the image processing units 102 to 110. The outline of the processing using the image processing unit and the memory will be described later.

The above-mentioned computer program PG is stored in the non-volatile memory 117. The computer program PG is a control program that allows the main processor 101 to control the multifunction device 100. The computer program PG is provided in a form stored in advance in the non-volatile memory 117 at the time of manufacturing the multifunction device 200. Instead of this, the computer program PG may be provided in a form downloaded from a server, or may be provided in a form stored in a DVD-ROM or the like.

The scanning execution unit 130 generates scan data by optically scanning the document using the one-dimensional image sensor under the control of the main processor 101. The scan data includes the values of a plurality of pixels, and each of the values of the plurality of pixels represents the color of the pixel as an RGB color value (also referred to as an RGB value). That is, the scan data is RGB image data. The RGB value of one pixel includes, for example, the values of three color components (hereinafter, also referred to as R value, G value, and B value) of red (R), green (G), and blue (B). I'm out. In this embodiment, the number of gradations of each component value is 256 gradations.

The print execution unit 140 uses a plurality of types of inks, specifically, cyan (C), magenta (M), yellow (Y), and black (K) inks as coloring materials under the control of the main processor 101. The image is printed by ejecting ink as a coloring material onto a printing medium such as paper (also called an inkjet method). In the modified example, the print execution unit 140 may be a laser-type print execution unit that prints an image on a print medium by a laser method using toner as a coloring material.

The communication IF 150 is an interface for communicating with an external device such as a user's terminal device (not shown), for example, a network interface according to an Ethernet (registered trademark) standard.

A-2. Outline of processing of the multifunction device 100 Copy processing executed by the multifunction device 100, that is, a process of generating scan data indicating a document using the scanning execution unit 130 and printing an image indicating the document using the scan data. The outline of is explained. The manuscript of this embodiment is, for example, a printed matter in which an image is printed by a multifunction device 100 or a printer (not shown).

The user sets the document to be copied on the sheet feeder of the scanning execution unit 130, and inputs the copying start instruction via an operation unit (not shown). The scanning execution unit 130 generates scan data as target image data by scanning the documents one by one in response to the start instruction. The generated scan data is output to the first input processing unit 102.

The first input processing unit 102 performs well-known image processing such as shading correction and color correction on the scan data output from the reading execution unit 130, and sends the image-processed scan data to the area separation processing unit 103. Send.

The area separation processing unit 103 performs the area separation processing on the scan data output from the first input processing unit 102. The area separation processing unit 103 detects image features such as a photograph (natural image) area, a character area, a halftone dot area, and a character area within the halftone dots for each pixel of the scanned image indicated by the scan data, and for each area. Flag data representing attributes is generated as the character flag 1007, the halftone dot flag 1008, and the halftone dot in-character flag 1009, which will be described later. The flag data is output to the second input processing unit 104 and stored in the first flag memory 112.

The second input processing unit 104 processes the scan data output from the first input processing unit 102 by performing appropriate image processing for each area based on the flag data output from the area separation processing unit 103. Generate finished image data. The processed image data is stored in the first image memory 111. For example, the second input processing unit 104 performs a process of emphasizing the high frequency component of the image to emphasize the sharpness of the character in the character area, and performs a low-pass filter process in the halftone dot area. The low-pass filter processing removes so-called moire components contained in the scanned image. The switching of these processes is performed on a pixel-by-pixel basis based on the flag data generated by the area separation processing unit 103.

When the processed image data for one page is stored in the first image memory 111, the data compression unit 107 compresses the processed image data by using, for example, a lossy compression method (for example, a PEG method). , The compressed processed image data is stored in the main memory 113.

When the flag data for one page is stored in the first flag memory 112, the data compression unit 107 compresses the flag data using a lossless compression method (for example, a ZIP method), and compresses the compressed flag data. , Stored in the main memory 113.

By performing the above processing, the compressed processed image data and the compressed flag data of each document are accumulated in the main memory 113. In parallel with this storage process, the data decoding unit 109 acquires the compressed processed image data and the compressed flag data from the main memory 113, and performs the decoding process. At this time, the resolution conversion unit 108 performs resolution conversion on the decoded processed image data to convert the resolution of the processed image data, if necessary.

The processed image data whose decoding and resolution have been converted is stored in the second image memory 116, and the decoded flag data is stored in the second flag memory 115.

The output processing unit 110 generates print data by executing a generation process including a color conversion process and a halftone process on the processed image data (RGB value) stored in the second image memory 116. In the process of generating print data, the output processing unit 110 refers to the flag data stored in the second flag memory 115, recognizes the attributes of the area to which each pixel belongs, and executes image processing suitable for each area. can do. As a result, appropriate print data is generated. The generated print data is output to the print execution unit 140. As a result, the print execution unit 140 prints an image showing the original on the paper.

The above was about copy processing, but the multifunction device 100 receives a print job transmitted from a terminal device such as a user's terminal device via the communication IF 150, and prints an image based on the print job. It also functions as a so-called network printer for printing.

In this case, the print job received via the communication IF 150 includes image data in PDL format. A print job containing image data in PDL format is supplied to the interpreter 106. The interpreter 106 interprets the PDL format image data included in the received print job and converts it into a drawing command (intermediate data) that can be interpreted by the RIP 105. The RIP 105 performs drawing processing (rasterization processing) based on this drawing command to generate RGB image data. This RGB image data is stored in the first image memory 111. The RIP 105 generates flag data and stores it in the first flag memory 112. In the print data in PDL format, characters, photographs (natural images), halftone dots, and the like are defined by print commands, so that the RIP 105 can easily generate flag data.

A-3. Processing by Area Separation Processing Unit 103 The processing executed by the area separation processing unit 103 will be described. FIG. 2 is a block configuration diagram of the area separation processing unit 103 in the embodiment.

A pixel-by-pixel input signal 1001 indicating the value of each pixel of the scan data output from the first input processing unit 102 is input to the brightness data acquisition unit 1002 for each pixel. That is, the input signal 1001 is a signal indicating the RGB value of each pixel of the scan data. The luminance data acquisition unit 1002 generates a signal indicating the luminance value, which is the degree of brightness of the pixels, as a pixel-based determination signal for attribute determination, based on the RGB value indicated by the input signal 1001. The luminance value is acquired by using a plurality of component values (R value, G value, B value) included in the RGB value. For example, the G value is used as the brightness value. Instead of this, the brightness value may be calculated by an operation such as (R + 2 × G + B) / 4. Further, the color value of the RGB color system may be converted into the color value of the Lab color system, and the obtained L value may be used as the luminance value. It can be said that the luminance data acquisition unit 1002 is a circuit that acquires luminance image data representing the luminance values of each of the plurality of pixels by using the scan data input for each pixel.

The determination signal indicating the luminance value generated by the luminance data acquisition unit 1002 is output to the character determination unit 1003, the halftone dot determination unit 1004, and the in-halftone dot character determination unit 1005, respectively. The character determination unit 1003, the halftone dot determination unit 1004, and the halftone dot internal character determination unit 1005 execute character determination, halftone dot determination, and halftone dot internal character determination, respectively, using the supplied determination signals. , The result signal indicating the determination result is output to the attribute flag generation unit 1006.

The attribute flag generation unit 1006 generates an attribute flag using the result signals from each determination unit 1003 to 1005. In the embodiment, the character flag 1007, the halftone dot flag 1008, and the halftone dot in-character flag 1009 are generated. The character flag 1007 is a flag indicating whether or not the corresponding pixel in the scan data is a character pixel constituting the character area. The halftone dot flag 1008 is a flag indicating whether or not the corresponding pixel in the scan data is a halftone dot pixel constituting the halftone dot region. The halftone dot character flag 1009 is a flag indicating whether or not the corresponding pixel in the scan data is a halftone dot character pixel constituting the halftone dot character area. Based on these attribute flags, it is possible to perform optimum image processing according to the characteristics of the image included in the scanned image. Hereinafter, the character determination unit 1003, the halftone dot determination unit 1004, and the halftone dot character determination unit 1005 will be described in more detail.

A-3-1. Explanation of Character Determination Unit 1003 FIG. 3 is a block diagram showing a configuration of the character determination unit 1003.

A determination signal (luminance value) from the luminance data acquisition unit 1002 is input to the edge enhancement unit 1102. The edge enhancement unit 1102 performs edge enhancement processing on the determination signal and outputs an edge enhancement signal. In this edge enhancement process, a filter process is performed to emphasize / extract a desired frequency component of the luminance image data. In this embodiment, a second derivative filter such as a Laplacian filter is used. For this purpose, the edge enhancement unit 1102 includes a buffer memory for storing a plurality of determination signals indicating the luminance values of the plurality of pixels of the luminance image data, which are necessary for the filtering process.

The edge enhancement signal output from the edge enhancement unit 1102 is input to the threshold value determination units 1103 and 1104 that compare the value indicated by the edge enhancement signal with the threshold value. A positive threshold value is set in the threshold value determination unit 1103, and a negative value threshold value is set in the threshold value determination unit 1104.

FIG. 4 is a diagram for explaining the processing of the character determination unit. When a second derivative filter is used in the edge enhancement process, the pixel value indicated by the edge enhancement signal may be a positive value or a negative value. In FIG. 4A, the edge boundary portion 1501 represents the edge of the character 1502 (for example, black) on the base 1503 (for example, white) and the base 1503. FIG. 4B shows the luminance image data (that is, the determination signal) 1504 corresponding to the cross section 1510 of the edge boundary portion 1501. In this example, the value (luminance value) of the luminance image data in the portion of the character 1502 is a relatively small value 1505, and the value of the luminance image data in the portion of the base 1503 is a relatively large value 1506. FIG. 4C shows edge extraction data 1507 (that is, data indicated by an edge enhancement signal) obtained by performing edge enhancement processing on the luminance image data 1504 of FIG. 4B using a second-order differential filter. )It is shown. The edge extraction data 1507 has a positive value 1508 on the character 1502 side and a negative value 1509 on the base 1503 side. The threshold value determination unit 1103 outputs an inner edge signal indicating "1" when the value indicated by the edge emphasis signal exceeds the positive threshold value, and indicates "0" when the value is equal to or less than the positive threshold value. Output the inner edge signal. The inner edge signal indicating "1" means that the corresponding pixel is a pixel on the small value side (inner edge pixel) constituting an edge that changes from a relatively small value to a relatively large value in the luminance image data. Is shown. In the example of FIG. 4, the pixel on the character side forming the edge between the character 1502 and the base 1503 is the inner edge pixel. The threshold value determination unit 1104 outputs an outer edge signal indicating "1" when the value indicated by the edge emphasis signal is below the negative threshold value, and indicates "0" when the value is equal to or greater than the negative threshold value. Output the outer edge signal. The outer edge signal indicating "1" is a pixel on the large value side (also referred to as an outer edge pixel) that constitutes an edge in which the corresponding pixel changes from a relatively small value to a relatively large value in the luminance image data. Indicates that there is. In the example of FIG. 4, the pixel on the base side forming the edge between the character 1502 and the base 1503 is the outer edge pixel.

The inner edge signal output from the threshold value determination unit 1103 is output to the area integration unit 1105, and the outer edge signal output from the threshold value determination unit 1104 is output to the area integration unit 1106. The area integration unit 1105 outputs an integration signal that integrates nine inner edge signals corresponding to pixels in the peripheral range of 3 vertical pixels × 3 horizontal pixels centered on the pixel of interest, for each pixel. The area integration unit 1106 outputs an integration signal obtained by integrating nine outer edge signals corresponding to the pixels in the peripheral range of the pixel of interest for each pixel. Therefore, the integrated signal output from the area integrating units 1105 and 1106 indicates the number of inner edge pixels and the number of outer edge pixels existing in the peripheral range of the corresponding pixels, respectively. Therefore, the value indicated by the integrated signal is in the range of 0 or more and 9 or less.

The threshold value determination unit 1107, 1108 compares the value indicated by the integration signal output from the area integration units 1105 and 1106 with the threshold value, and outputs an integration determination signal indicating the result. For example, a value of "2" is set as the threshold value. Therefore, the integration determination signal output from the threshold value determination unit 1107 has a positive value (for example, "1") when there are two or more inner edge pixels within the peripheral range of the corresponding pixels. Shown. The integration determination signal output from the threshold value determination unit 1108 shows a positive value (for example, “1”) when there are two or more outer edge pixels within the peripheral range of the corresponding pixel.

A specific example of the process will be described with reference to FIG. FIG. 5 is a diagram showing signals of each process of the character determination unit. FIG. 5A shows a part 1301 of the edge of the character on the background that appears in the luminance image indicated by the luminance image data.

FIG. 5B shows the result of edge-enhancing the determination signal (that is, the signal indicating the luminance value) by the edge enhancement unit 1102 and processing by the threshold value determination unit 1104, that is, the specific result of the outer edge pixel. As shown, the region 1302 represents a region (outer edge region) outside the edge of the character.

FIG. 5C shows the result of processing the outer edge signal from the threshold value determination unit 1104 by the area integration unit 1106 and processing the integration signal from the area integration unit 1106 by the threshold value determination unit 1108, that is, the area integration of the outer edge. The judgment result of is shown. As shown, region 1304 is the result of expansion of outer edge region 1302.

FIG. 5D shows the result of edge-enhancing the determination signal (that is, the signal indicating the minimum component value Vmin) by the edge enhancement unit 1102 and processing by the threshold value determination unit 1103, that is, the specific result of the inner edge pixel. There is. As shown, the area 1303 represents an area inside the edge of the character (inner edge area).

FIG. 5 (E) shows the result of processing the inner edge signal from the threshold value determination unit 1103 by the area integration unit 1105 and processing the integration signal from the area integration unit 1105 by the threshold value determination unit 1107, that is, the area integration of the inner edge. The judgment result of is shown. As shown, the region 1305 is the result of the expansion of the inner edge region 1303.

Three types of signals output from the threshold value determination units 1103, 1107, and 1108, that is, an inner edge signal, an inner edge integration determination signal, and an outer edge integration determination signal, are input to the comprehensive determination unit 1109. To. The comprehensive determination unit 1109 generates the character determination signal 1110, which is a result signal indicating the determination result of the character determination unit 1003. FIG. 5F shows a region 1306 indicated as a character by a character determination signal.

The comprehensive determination unit 1109 outputs the character determination signal 1110 according to a determined logic based on the inner edge signal, the inner edge integration determination signal, and the outer edge integration determination signal. For example, the character determination signal 1110 can be a signal indicating that it is a character (“1” in this embodiment) or a signal indicating that it is not a character (“0” in this embodiment) with the following logic. It is determined.
(1) The corresponding pixel is the inner edge. → "1"
(2) The corresponding pixel is an outer edge, and there are two or more outer edges in the peripheral range of the vertical 3 pixels × vertical 3 pixels. → "0"
(3) It does not correspond to any of the above (1) and (2), and there are two or more inner edges in the peripheral range of the above 3 vertical pixels × 3 vertical pixels. → "1"
(4) It does not correspond to any of the above (1) to (3). → "0"
In order to realize the above, the comprehensive determination unit 1109 holds the table shown in FIG. As shown in the figure, the character determination signal 1110 is determined according to the results of the input inner edge signal, inner edge integration determination signal, and outer edge integration determination signal. By performing as described above, characters can be suitably extracted.

A-3-2. Explanation of Halftone Halftone Halftone Point Determination Unit 1004 FIG. 7 is a block configuration diagram of the halftone dot determination unit 1004 in the embodiment.

A determination signal (luminance value) from the luminance data acquisition unit 1002 is input to the edge enhancement unit 1202. The edge enhancement unit 1202 performs edge enhancement processing on the determination signal and outputs the edge enhancement signal. The edge enhancement process by the edge enhancement unit 1202 is the same process as the edge enhancement process by the edge enhancement unit 1102 in FIG. 3, and is, for example, a filter process using a second derivative filter such as a Laplacian filter.

The edge enhancement signal output from the edge enhancement unit 1202 is input to the threshold value determination units 1203 and 1204 that compare the value indicated by the edge enhancement signal with the threshold value. A positive threshold value is set in the threshold value determination unit 1203, and a negative value threshold value is set in the threshold value determination unit 1204.

FIG. 8 is a diagram for explaining the processing of the halftone dot determination unit. When a second-order differential filter is used in the edge enhancement process, the pixel value indicated by the edge enhancement signal may be a positive value or a negative value, as described above. In FIG. 8A, the edge boundary portion 1601 represents the edge of one halftone dot 1602 on the base 1603 (for example, white) and the base 1603. FIG. 8B shows the luminance image data (that is, the determination signal) 1604 with respect to the cross section 1610 of the halftone dot edge boundary portion 1601. In this example, the luminance image data value (luminance value) at the halftone dot 1602 portion is a relatively small value 1605, and the luminance image data value at the base 1603 portion is a relatively large value 1606. FIG. 8C shows edge extraction data 1607 obtained by performing edge enhancement processing on the luminance image data 1604 of FIG. 8B using a second-order differential filter. The edge extraction data 1607 has a positive value 1608 on the halftone dot 1602 side and a negative value 1609 on the base 1603 side. The threshold value determination unit 1203 outputs an inner edge signal in the same manner as the threshold value determination unit 1103 of FIG. The threshold value determination unit 1204 outputs an outer edge signal in the same manner as the threshold value determination unit 1104 of FIG. In the example of FIG. 6, the halftone dot side pixels forming the edge between the halftone dot 1602 and the base 1603 are the inner edge pixels. Further, the pixels on the base side forming the edge between the halftone dots 1602 and the base 1603 are outer edge pixels.

The inner edge signal output from the threshold value determination unit 1203 is input to the isolation amount determination unit 1205. The outer edge signal output from the threshold value determination unit 1204 is input to the isolation amount determination unit 1206.

The isolation amount determination unit 1205 performs pattern matching processing on the inner edge signal from the threshold value determination unit 1203. Since the halftone dots included in the manuscript range from those having a relatively small number of lines per unit area to those having a relatively large number of lines per unit area, the size and spacing of the halftone dots differ depending on the manuscript. Therefore, pattern matching is performed with a plurality of patterns so that halftone dots of any number of lines can be detected. For halftone dots with a small number of lines, matching is performed with a relatively large pattern to determine whether or not the dots are halftone dots. For halftone dots with a large number of lines, matching is performed with a relatively small pattern to determine whether or not the dots are halftone dots. In addition, since the shape of halftone dots changes depending on the density to be expressed on the document, a plurality of judgment levels are used at the time of matching so as to cope with it.

FIG. 9 is a first diagram showing an example of pattern matching. FIG. 9A is an example of the result of the threshold value determination unit 1203. FIG. 9A shows an inner edge signal 1700 in the range of 4 vertical pixels × 4 horizontal pixels in order to explain an example of pattern matching. Among them, the pixels (inner edge pixels) to which the inner edge signal indicating "1" is output by the threshold value determination unit 1203 are the four pixels of the hatched region 1702. The pixel (non-inner edge pixel) to which the inner edge signal indicating "0" is output is a pixel in the unhatched area 1703. The pixel of interest to be matched is pixel 1701.

Next, an example of the determination pattern of the same size is shown in FIG. 9B. In the illustrated determination pattern 1710, the four black pixels 1712 are pixels that should be inner edge pixels in the pattern. The eight white pixels 1713 are pixels that should be non-inner edge pixels. The pixels at the four corners are arbitrary pixels 1714 which may be inner edge pixels or non-inner edge pixels. Using this as a basic pattern, the black pixel 1712 and the white pixel 1713 are each provided with a plurality of matching levels, and the determination level is adjusted.

FIG. 10 is a diagram showing an example of the matching result of the inner edge signal, the determination pattern 1710 of FIG. 9B.

When the black pixel 1712 in the determination pattern 1710 and the inner edge pixel in the inner edge signal match k1 pixel (k1 is an integer of 1 or more and 3 or less) or more of the four pixels, the black pixel determination is valid. .. When the white pixel 1713 in the determination pattern 1710 and the non-edge pixel in the inner edge signal match k2 pixels or more (k2 is an integer of 1 or more and 7 or less) out of 8 pixels, the white pixel determination is valid. Only when both the black pixel determination and the white pixel determination are valid, the isolated amount determination signal indicating the determination result of the attention pixel 1801 is set to "1". The determination level can be arbitrarily adjusted by adjusting the values of k1 and k2. In this embodiment, k1 = 3 and k2 = 6.

In the case of the inner edge signal 1810 of FIG. 10A, the black pixel determination is valid (match number = 4) and the white pixel determination is valid (match number = 8), so that the isolation amount determination signal is ". 1 ”.

In the case of the inner edge signal 1820 of FIG. 10B, the black pixel determination is valid (match number = 4) and the white pixel determination is valid (match number = 7), so that the isolation amount determination signal is “ 1 ”.

In the case of the inner edge signal 1830 of FIG. 10C, the black pixel determination is valid (match number = 3) and the white pixel determination is valid (match number = 8), so that the isolation amount determination signal is ". 1 ”.

In the case of the inner edge signal 1840 of FIG. 10D, the black pixel determination is invalid (match number = 2) and the white pixel determination is valid (match number = 8), so that the isolation amount determination signal is ". It becomes "0".

Such pattern matching is performed using determination patterns of a plurality of sizes. In the embodiment, the inner edge signal has been described, but the same pattern matching is performed for the outer edge signal. At that time, the determination pattern and the adjustment value of the determination level can be arbitrarily set.

By the way, the isolation amount determination signal output from the isolation amount determination units 1205 and 1206 is input to the OR processing unit 1207 of FIG. 7. The OR processing unit 1207 takes the logical sum of the isolation amount determination signals within the range of 3 vertical pixels × 3 horizontal pixels, and determines whether or not there is a pixel whose isolation amount determination signal is “1” in the range. .. As a result of the determination, the OR processing unit 1207 sets the OR processing signal of the pixel of interest to be determined to be "1" if there is one or more pixels in the range in which the isolation amount determination signal is "1", and the isolation amount. If there is no pixel in the range in which the determination signal is "1", the OR processing signal of the pixel of interest to be determined is set to "0".

FIG. 11 is an explanatory diagram of processing by the OR processing unit 1207. In the example of FIG. 11A, only the isolation amount determination signal of the central attention pixel in the range of 3 vertical pixels × 3 horizontal pixels is “1”. Therefore, the output OR processing signal is "1". In the example of FIG. 11B, the isolation amount determination signal of the central attention pixel is "0", but the isolation amount determination signal of the upper right pixel within the range of 3 vertical pixels x 3 horizontal pixels is "1". Is. Therefore, the output OR processing signal is "1". In the example of FIG. 11C, the isolation amount determination signal of the central pixel of interest is “0”, but the isolation amount determination signal of the eight pixels around it is “1”. Therefore, the output OR processing signal is "1".

The OR processing signal output from the OR processing unit 1207 is input to the integration processing unit 1209. FIG. 12 is a block diagram showing the configuration of the integration processing unit 1209 and the threshold value determination unit 1211.

The integration processing unit 1209 outputs an integration signal obtained by integrating a plurality of OR processing signals corresponding to pixels within the integration range of a plurality of types of sizes centered on the pixel of interest for each pixel. The integration processing unit 1209 integrates the OR processing signal signal using a plurality of integration ranges. For example, the first integration unit 2011 uses a range of 9 vertical pixels × 9 horizontal pixels as the integration range. Therefore, the integration determination signal output from the first integration unit 2011 is in the range of 0 or more and 81 or less. The second integration unit 2012 and the third integration unit 2013 use a range of vertical 15 pixels × horizontal 15 pixels and a range of vertical 21 pixels × horizontal 21 pixels, respectively, as the integration range. Therefore, the integrated signals output from the second integrating unit 2012 and the third integrating unit 2013 are in the range of 0 or more and 225 or less and 0 or more and 441 or less, respectively. The integrated signals output from the first integrating unit 2011, the second integrating unit 2012, and the third integrating unit 2013 are sent to the first determination unit 2021, the second determination unit 2022, and the third determination unit 2023 of the threshold value determination unit 1211, respectively. , Is entered.

The first determination unit 2021, the second determination unit 2022, and the third determination unit 2023 compare the value indicated by the integration signal input to each with the threshold value, and output an integration determination signal indicating the result. I do. Specifically, when the value indicated by the integration signal is equal to or greater than the set threshold value, the integration determination signal output from the first determination unit 2021, the second determination unit 2022, and the third determination unit 2023 is ". It is set to "1", and if it is less than the threshold value, it is set to "0". The threshold values used in the first determination unit 2021, the second determination unit 2022, and the third determination unit 2023 are different values from each other, and are set to "5", "12", and "23", respectively, in this embodiment. ing. As a result, each determination unit 2021, 2022, 2023 outputs an integration determination signal indicating "1" when the value indicated by the integration signal exceeds about 5% of the number of pixels in the integration range, and the integration signal is generated. When the indicated value is about 5% or less of the number of pixels in the integration range, an integration determination signal indicating "0" is output.

The integrated determination signals output from the first determination unit 2021, the second determination unit 2022, and the third determination unit 2023 are input to the comprehensive determination unit 1213 (FIGS. 7 and 12). The comprehensive determination unit 1213 generates a halftone dot determination signal 1215, which is a result signal indicating the determination result of the halftone dot determination unit 1004, based on the three input integration determination signals. The halftone dot determination signal 1215 is either a value "1" indicating that the pixel of interest is a halftone dot pixel or a value "0" indicating that the pixel of interest is not a halftone dot pixel.

13 to 15 are diagrams showing an example of processing of the threshold value determination unit 1211 and the comprehensive determination unit 1213. FIG. 13A conceptually illustrates the OR processing signal 2100 output by the OR processing unit 1207. The OR processing signal 2100 is an example in which a region including halftone dots showing a relatively low density is processed. The cross-hatched pixel indicates a pixel whose corresponding OR processing signal is "1", and the non-cross-hatched pixel indicates a pixel whose corresponding OR processing signal is "0". In the figure, the integration range 2102 of 9 pixels vertically × 9 pixels horizontally, the integration range 2103 of 15 pixels vertically × 15 pixels horizontally, and the integration range 2104 of 21 pixels vertically × 21 pixels horizontally, centered on the pixel of interest 2101. , Are shown respectively. The integration results in each integration range, that is, the values of the integration signals output from the first integration unit 2011, the second integration unit 2012, and the third integration unit 2013 are shown in FIG. 13 (B). The integration result of the first integration unit 2011 (9 × 9) is 12 pixels, the integration result of the second integration unit 2012 (15 × 15) is 40 pixels, and the integration result of the third integration unit 2013 is. It has 76 pixels.

Therefore, as shown in FIG. 13B, the integration result “12” of the first integration unit 2011 (9 × 9) is equal to or higher than the threshold value “5”, so that the first determination unit 2021 (9 × 9) The integrated determination signal to be output is "1" (halftone dot). Similarly, the integration result “40” of the second integration unit 2012 (15 × 15) is also the threshold value “12” or more, and the integration result “76” of the third integration unit 2013 (21 × 21) is also the threshold value “23”. Therefore, the integration determination signals output by the corresponding second determination unit 2022 and third determination unit 2023 are both “1”.

Based on the above three types of results, the comprehensive determination unit 1213 finally determines whether or not the pixel of interest is a halftone dot, and generates a halftone dot determination signal 1215 indicating the determination result. In this embodiment, the comprehensive determination unit 1213 makes two pairs from the three types of results, as shown in FIG. 13 (C). For example, the integration determination signal of the first determination unit 2021 and the second determination unit 2022 makes a first pair, and the integration determination signal of the second determination unit 2022 and the third determination unit 2023 makes a second pair. The comprehensive determination unit 1213 calculates the logical product (AND) of each set of integration determination signals. The logical product of the first pair is "1" (halftone dots), and the logical product of the second pair is also "1" (halftone dots). The comprehensive determination unit 1213 further generates the logical sum of the logical product of the first pair and the logical product of the second pair as the halftone dot determination signal 1215. In the example of FIG. 13, since each logical product is “1”, the halftone dot determination signal 1215 of the pixel of interest becomes “1” (halftone dot).

FIG. 14 (A) conceptually illustrates an OR processing signal 2200 that includes halftone dots showing the same density as that of FIG. 13 and corresponds to a region including a character edge 2205. As shown in the figure, when there is a character edge 2205, an isolated dot is not generated in the vicinity of the edge, so that the OR processing signal in the vicinity of the character edge becomes “0”. In this case, as shown in FIG. 14B, the integration result of the first integration unit 2011 (9 × 9) is 4 pixels, and the integration result of the second integration unit 2012 (15 × 15) is. It has 32 pixels, and the integration result of the third integration unit 2013 is 60 pixels.

Therefore, as shown in FIG. 14B, the integration result “4” of the first integration unit 2011 (9 × 9) is less than the threshold value “5”, so that the first determination unit 2021 (9 × 9) The integrated determination signal to be output is "0" (non-halftone dot). The integration result "32" of the second integration unit 2012 (15 × 15) is the threshold value “12” or more, and the integration result “60” of the third integration unit 2013 (21 × 21) is also the threshold value “23” or more. Therefore, the integration determination signals output by the corresponding second determination unit 2022 and third determination unit 2023 are both "1" (halftone dots).

As shown in FIG. 14C, the logical product of the first pair is "0" (non-halftone dots), and the logical product of the second pair is "1" (halftone dots). The logical sum of the logical product of the first pair and the logical product of the second pair is, that is, the halftone dot determination signal 1215 of the pixel of interest becomes "1" (halftone dot). As described above, since the edge of the character is included, even if the integration result of one integration range indicates a non-halftone dot, it is finally determined to be a halftone dot. In this way, by using a plurality of integration ranges and a plurality of threshold values, it can be appropriately detected as halftone dots.

FIG. 15A conceptually illustrates the OR processing signal 2300 when the pixel of interest is outside the edge of the region including the halftone dots showing the same density as that of FIG. 13A. In this case, as shown in FIG. 15B, the integration result of the first integration unit 2011 (9 × 9) is 0 pixels, and the integration result of the second integration unit 2012 (15 × 15) is. There are 12 pixels, and the integration result of the third integration unit 2013 is 20 pixels.

Therefore, as shown in FIG. 15B, the “0” of the integration result of the first integration unit 2011 (9 × 9) is less than the threshold value “5”, so that the first determination unit 2021 (9 × 9) The integrated determination signal to be output is "0" (non-halftone dot). Since the integration result “12” of the second integration unit 2012 (15 × 15) is equal to or greater than the threshold value “12”, the integration determination signal output by the second determination unit 2022 (15 × 15) is “1” (net). Point). Since the integration result “20” of the third integration unit 2013 (21 × 21) is less than the threshold value “23”, the integration determination signal output by the third determination unit 2023 (21 × 21) is “0” (non-). It becomes a halftone dot).

As shown in FIG. 15C, the logical product of the first pair is "0" (non-halftone dots), and the logical product of the second pair is also "0" (non-halftone dots). The logical sum of the logical product of the first pair and the logical product of the second pair, that is, the halftone dot determination signal 1215 of the pixel of interest is "0" (non-halftone dot). When a character edge is included in the halftone dot area included in the integration range as in the example of FIG. 14, the halftone dot at the position overlapping the character edge is removed by the character edge, so that the halftone dot in the integration range is excluded. The total number of Here, when the integration range is expanded, the total number of halftone dots included in the integration range increases, so that the ratio of the number of halftone dots excluded by the character edge to the total number of halftone dots decreases. As a result, the pixels in the halftone dot region can be appropriately determined as halftone dots. However, when the integration range is expanded, pixels far outward from the edge of the region including the halftone dots can also be determined to be halftone dots, so that the region determined to be halftone dots can be expanded. In this embodiment, by using a plurality of integration ranges and a plurality of threshold values, pixels outside the edge of halftone dots can be appropriately detected as non-halftone dots.

The combination of integration processing described here is only an example, and is not limited to this. The combination can be freely configured according to the purpose. Further, in the explanation, since the results of three types of integration processing are used, two sets of logical products are used, but the present invention is not limited to this. The number of inputs and its logical operation unit can be freely configured. Furthermore, the combination of the logical product and the logical ring is only an example, and is not limited to this. You can freely combine logical products and ORs.

A-3-2. Explanation of Halftone Halftone Character Determination Unit 1005 FIG. 16 is a block diagram showing a configuration of halftone dot character determination unit 1005.

The adaptive smoothing processing unit 2401 inputs a determination signal (luminance value) from the luminance data acquisition unit 1002 and performs adaptive smoothing processing. Here, digital filtering is performed to smooth the desired frequency component of the scan data while adaptively excluding characters / thin lines.

The smoothing signal output from the adaptive smoothing processing unit 2401 is input to the edge enhancing unit 2402. The edge enhancement unit 2402 performs edge enhancement processing on the smoothing signal and outputs the edge enhancement signal. The edge enhancement process by the edge enhancement unit 2402 is the same process as the edge enhancement process by the edge enhancement unit 1102 in FIG. 3, and is, for example, a filter process using a second-order differential filter such as a Laplacian filter.

The edge enhancement signal output from the edge enhancement unit 2402 is input to the threshold value determination unit 2403. A positive threshold value is set in the threshold value determination unit 2403.

As described with reference to FIG. 4, when a second derivative filter is used in the edge enhancement process, the pixel value indicated by the edge enhancement signal may be a positive value or a negative value. is there. As shown in FIG. 4B, when the characters are represented by a dark color and the background is represented by a light color, the edge extraction data 1507 (1507) obtained by performing edge enhancement processing using a second-order differential filter. That is, the data indicated by the edge enhancement signal) has a positive value 1508 on the character 1502 side and a negative value 1509 on the base 1503 side. On the contrary, when the character is represented by a light color and the background is represented by a dark color, the edge extraction data has a negative value corresponding to the outer edge on the character side and corresponds to the inner edge on the background side. It becomes a positive value (not shown).

The halftone dot character determination does not aim to distinguish whether the edge is on the character side or the base side, but aims to extract the character itself in the halftone dot area. In this case, one of a positive edge (that is, an inner edge) and a negative edge (that is, an outer edge) may be detected. In this embodiment, the inner edge is detected. Specifically, the threshold value determination unit 2403 outputs an inner edge signal indicating "1" when the value indicated by the edge emphasis signal exceeds the positive threshold value, and outputs an inner edge signal indicating "1" when the value is equal to or less than the positive threshold value. The inner edge signal indicating "0" is output. However, the threshold value determination unit 2403 may detect a negative edge (outer edge) without detecting a positive edge (inner edge), and the positive edge (inner edge) and the negative edge (outer edge) Both may be detected. Hereinafter, the above processing will be described in more detail.

FIG. 17 is a block diagram showing the configuration of the adaptive smoothing processing unit 2401. The adaptive smoothing processing unit 2401 includes a smoothing processing unit 2502, two line determination units 2503a and 2503b, a selector 2504, and an inversion processing unit 2507. The first line determination unit 2503a and the second line determination unit 2503b are the same circuit in this embodiment. The determination signal 2501 (luminance value) from the luminance data acquisition unit 1002 is branched into four and input to the smoothing processing unit 2502, the selector 2504, the first line determination unit 2503a, and the inversion processing unit 2507, respectively. Will be done.

The smoothing processing unit 2502 sets the value of a plurality of pixels within the filter range of vertical L pixel × horizontal L pixel (L is an integer of 2 or more) centered on the pixel of interest to be processed with respect to the determination signal 2501. Is used to execute the smoothing process. The smoothing process is a process for reducing the sensitivity of a specific frequency band. For example, the smoothing process may be a process using a Gaussian filter or a process using an average value filter. The smoothing processing unit 2502 supplies a smoothing signal indicating the result of the smoothing processing to the selector 2504.

The determination signal 2501 input to the selector 2504 is delayed by passing through a delay memory (not shown) in order to correspond to an image delay according to the number of processing lines processed by the smoothing processing unit 2502, and then the selector 2504 Is entered in.

The first line determination unit 2503a utilizes a determination signal (luminance value Yx) stored in the processing buffer for L lines of processing by the smoothing processing unit 2502, and uses vertical L1 pixels × horizontal L2 pixels (L2, In the processing region of (L1 is an integer of 2 or more, preferably L1 ≦ L), it is determined whether or not the pixel of interest is a pixel on a vertical line, a horizontal line, or an oblique line represented by a dark color. The first line determination unit 2503a outputs a first switching signal to the selector 2504 according to the determination result for these dark lines. When the first line determination unit 2503a determines that the pixel of interest is a line pixel on these dark lines, it outputs a first switching signal indicating "1", and the pixel of interest must be a pixel on the dark line. If it is determined, the first switching signal indicating "0" is output.

The inversion processing unit 2507 inverts the determination signal 2501 indicating the luminance value to generate an inversion determination signal indicating the inversion luminance value. Assuming that the luminance value is Y, the inverted luminance value Yx is expressed by the following equation (1).
Yx = Ymax-Y ... (1)
Here, Ymax is the maximum value that the luminance value Y can take, and in this embodiment, Ymax = 255. It is said that the inversion processing unit 2507 is a circuit that generates inversion luminance image data which is image data in which the inversion luminance value Yx is the value of a plurality of pixels by using the luminance image data input for each pixel. Can be done. The inversion determination signal indicating the inversion luminance value Yx generated by the inversion processing unit 2507 is input to the second line determination unit 2503b.

The second line determination unit 2503b utilizes an inversion determination signal (inverted luminance value Yx) stored in a processing buffer for L lines different from the smoothing processing unit 2502, and has vertical L1 pixels × horizontal L2 pixels. In the processing region (L2 and L1 are integers of 2 or more, L1 ≦ L is preferable), for the pixel of interest, on the vertical line, horizontal line, and diagonal line represented by a dark color as in the first line determination unit 2503a. It is determined whether or not the pixel is. The second line determination unit 2503b outputs a second switching signal to the selector 2504 according to the determination result for these dark lines. When the second line determination unit 2503b determines that the pixel of interest is a line pixel on these dark lines, it outputs a second switching signal indicating "1", and the pixel of interest must be a pixel on the dark line. If it is determined, a second switching signal indicating "0" is output.

Here, in the inverted luminance image indicated by the inverted luminance image data (inverted luminance value Yx), the bright portion of the luminance image indicated by the luminance image data before inversion is a dark portion, and the dark portion is a bright portion. Therefore, the dark lines in the inverted luminance image correspond to the bright lines in the luminance image. Therefore, when the second line determination unit 2503b determines that the pixel of interest in the inverted luminance image is a line pixel on a dark line, it determines that the corresponding pixel in the luminance image is a line pixel on a bright line. Equal to doing. In other words, the two line determination units 2503a and 2503b can identify both the line pixels on the dark line in the luminance image and the line pixels on the bright line in the luminance image.

The selector 2504 has a smoothing signal output from the smoothing processing unit 2502 and a filter based on the first switching signal and the second switching signal output from the first line determination unit 2503a and the second line determination unit 2503b, respectively. Either the unprocessed determination signal 2501 or the unprocessed determination signal 2501 is output. The selector 2504 determines that at least one of the first switching signal and the second switching signal is "1", that is, when the first line determination unit 2503a determines that the pixel of interest is a line pixel. When the 2-line determination unit 2503b determines that the pixel of interest is a line pixel, the determination signal 2501 which is not filtered is output. The selector 2504 determines that both the first switching signal and the second switching signal are "0", that is, the pixel of interest is neither a line pixel on a dark line nor a line pixel on a bright line. Outputs a smoothing signal.

The first line determination unit 2503a will be described. The first line determination unit 2503a determines whether or not the pixel of interest is a line pixel by using a line pattern as shown in FIGS. 18A to 18D. The size of the line pattern is the size of the above-mentioned vertical L1 pixel × horizontal L2 pixel. In the example of FIG. 18, L1 = 5 and L2 = 7. The number of pixels L1 in the vertical direction (sub-scanning direction) is preferably smaller than the number of pixels L in the sub-scanning direction of the filter range processed by the smoothing processing unit 2502 from the viewpoint of sharing memory, but is not limited thereto. The number of pixels L2 in the lateral direction (main scanning direction) may be larger than L.

The line pattern 2600 of FIG. 18A shows a line pattern for determining a vertical line, and the line pattern 2610 of FIG. 18B shows a line pattern for determining a horizontal line. The line patterns 2620 and 2630 in FIGS. 18 (C) and 18 (D) represent line patterns for determining diagonal lines having different extending directions. Here, a method for determining vertical lines will be described using the line pattern 2600. Pixels 2601, 2611, 2621, 2631 indicate pixels of interest.

The pattern 2600 has a size of 5 pixels in the vertical direction and 7 pixels in the horizontal direction. The line pattern 2600 includes blocks 2602, 2603, and 2604 having 5 vertical pixels and 1 horizontal pixel. The pixel of interest 2601 is arranged at the center of the central block 2603 of the blocks 2602, 2603, and 2604 arranged in the horizontal direction. The first line determination unit 2503a calculates the total value (ALL), the maximum value (MAX), and the minimum value (MIN) of the values indicated by the determination signal 2501 for each block. That is, for each block, the sum total, maximum value, and minimum value of the brightness values of the pixels in the block are calculated.

The first line determination unit 2503a evaluates the following conditional expression.
(1) MAX (2602) -MIN (2602) ≤ threshold value 1
(2) MAX (2603) -MIN (2603) ≤ threshold value 1
(3) ALL (2603) ≤ ALL (2602) -threshold value 2
Condition (1) evaluates that there is no difference in pixel values for 5 pixels in the block 2602. Condition (2) evaluates that there is no difference in pixel values for the five pixels in the block 2603. Condition (3) compares the sum of the pixel values in the block 2602 with the sum of the pixel values in the pixel block 2603, and the pixel block 2603 is relative to the pixel block 2602 in terms of pixel values. Evaluate that it is low. When all the conditions (1) to (3) are satisfied, the pixel block 2603 is determined to form a dark vertical line. When the conditions (1) to (3) are satisfied, the block 2603 is a low-luminance region in which a plurality of pixels having a brightness less than the reference are continuous. Therefore, it can be said that the conditions (1) to (3) are determination conditions indicating that the pixel of interest is in the low-luminance region. Specifically, in this embodiment, there is no significant difference in the luminance of the plurality of pixels in the block 2602, that is, the plurality of peripheral pixels including the adjacent pixels (condition (1)), and the judgment target. There is no significant difference in the brightness of the plurality of pixels in the block 2603 (condition (2)), and the brightness of the plurality of pixels in the block 2603 is higher than the brightness of the plurality of peripheral pixels in the block 2602. However, when it is significantly low (condition (3)), the block 2603 is determined to be a region in which a plurality of pixels having a brightness less than the reference are continuous. Specific conditions (1) to (3) indicating that the pixel of interest is within the low-luminance region are examples, and various other conditions can be used as described later.

The first line determination unit 2503a evaluates the following conditional expression.
(4) MAX (2604) -MIN (2604) ≤ threshold value 1
(5) MAX (2603) -MIN (2603) ≤ Threshold 1
(6) ALL (2603) ≤ ALL (2604) -threshold value 2
Condition (4) evaluates that there is no difference in pixel values for the five pixels in the block 2604. Condition (5) evaluates that there is no difference in pixel values for 5 pixels in the block 2603. Condition (6) compares the sum of the pixel values in the block 2604 with the sum of the pixel values in the pixel block 2603, and the pixel block 2603 is relative to the pixel block 2604 in terms of pixel values. Evaluate that it is low. When all the conditions (4) to (6) are satisfied, the pixel block 2603 is determined to form a dark vertical line. It can be said that the conditions (4) to (6) are the determination conditions indicating that the pixel of interest is in the low-luminance region, as in the above conditions (1) to (3).

As a result of evaluating the conditions (1) to (3) or the conditions (4) to (6), if it is determined that the block 2603 constitutes a dark vertical line in any one of them, the first line The determination unit 2503a determines that the pixel of interest 2601 is a line pixel located on the vertical line.

FIG. 19 is a diagram showing an example of determination using the line pattern 2600 of FIG. 18 (A). 19 (A) to 19 (C) show determination signals (luminance values) 2700, 2710, and 2720 in a region of 5 vertical pixels and 7 horizontal pixels corresponding to the line pattern 2600. The determination signal 2700 indicates an image of a portion having a dark vertical line on a white background. The plurality of hatched pixels form a vertical line. For convenience of explanation, when the determination signal indicates a value of 256 gradations from 0 to 255, the white pixel has the corresponding determination signal value of "255", and the single-hatched pixel has the corresponding determination. It is assumed that the value of the signal is "128" and the value of the corresponding determination signal is "0" for the cross-hatched pixels. Further, it is assumed that the threshold value 1 of the above conditions (1) to (6) is 20 and the threshold value 2 is 200.

The results of applying the above conditions (1) to (6) to the determination signal 2700 and determining the authenticity are as follows.
(1) MAX (2702) -MIN (2702) ≤ threshold value 1
128-128 ≤ 20 → True (2) MAX (2703) -MIN (2703) ≤ Threshold 1
0-0 ≤ 20 → True (3) ALL (2703) ≤ ALL (2702) -Threshold 2
0 × 5 ≤ 128 × 5-200 → True (4) MAX (2704) -MIN (2704) ≤ Threshold 1
128-128 ≤ 20 → True (5) MAX (2703) -MIN (2703) ≤ Threshold 1
0-0 ≤ 20 → True (6) ALL (2703) ≤ ALL (2704) -Threshold 2
0 × 5 ≦ 128 × 5-200 → True As described above, since the conditions (1) to (3) are all true, it is determined that the pixel of interest is a line pixel located on the vertical line. Further, since the conditions (4) to (6) are all true, it is determined that the pixel of interest is a line pixel located on the vertical line from this condition as well.

The determination signal 2710 in FIG. 19B shows an image of a portion having a dark horizontal line on a white background. The results of applying the above conditions (1) to (6) to the determination signal 2710 and determining the authenticity are as follows. (1) False, (2) False, (3) False, (4) False, (5) False, (6) False As a result, it is determined that the pixel of interest is not a line pixel located on the vertical line.

The determination signal 2720 of FIG. 19C shows an image of a portion having a dark diagonal line on a white background. The results of applying the above conditions (1) to (6) to the determination signal 2720 and determining the authenticity are as follows.
(1) False, (2) False, (3) True, (4) False, (5) False, (6) True As a result, it is determined that the pixel of interest is not a line pixel located on the vertical line.

FIG. 20 is a diagram showing an example of determination using the line patterns 261 to 2630 of FIGS. 18 (B) to 18 (D). The determination signal 2810 in FIG. 20A shows an image of a portion having a horizontal line on a white background. The determination signals 2820 and 2830 of FIGS. 20 (B) and 20 (C) show images of portions having diagonal lines on a white background. Also in the line patterns 261 to 2630, the pixels of interest 2611, 2621, and 2631 are arranged at the center of the central blocks 2613, 2623, and 2633 of the three blocks arranged in the direction perpendicular to the extending direction of the line. .. Then, in the examples of FIGS. 20A to 20C, although the details are omitted, it is determined that all the pixels of interest are line pixels.

The second line determination unit 2503b uses the inversion determination signal indicating the inversion luminance value Yx instead of the determination signal indicating the luminance value Y, and the same conditions (1) to (3) as those of the first line determination unit 2503a and By judging about (4) to (6), it is judged whether or not the pixel of interest is a line pixel.

FIG. 21 is a diagram showing an example of determination using the line pattern 2600 of FIG. 18 (A). 21 (A) to 21 (C) show determination signals (luminance value Y) 2700w, 2710w, 2720w in a region of 5 vertical pixels × 7 horizontal pixels corresponding to the line pattern 2600. The determination signal 2700w indicates an image of a portion having a bright color vertical line on a black background. A plurality of pixels without hatching form a vertical line. Similar to the example of FIG. 19, the determination signal shows a value of 256 gradations from 0 to 255, the white pixel has the corresponding determination signal value of “255”, and the single-hatched pixel corresponds. It is assumed that the value of the determination signal is "128" and the value of the corresponding determination signal is "0" for the cross-hatched pixels. The inversion determination signal (inverted luminance value Yx) obtained by inverting the determination signals (luminance values Y) 2700w, 2710w, 2720w of FIGS. 21 (A) to 21 (C) is the determination of FIGS. 19 (A) to 19 (C). It becomes the same as the signal (luminance value Y) 2700, 2710, 2720. Therefore, in the example of FIG. 21A, the pixel of interest is determined by the second line determination unit 2503b to be a line pixel located on the vertical line. Further, in the examples of FIGS. 21B and 21C, it is determined that the pixel of interest is not a line pixel located on the vertical line.

FIG. 22 is a diagram showing an example of determination using the line patterns 261 to 2630 of FIGS. 18 (B) to 18 (D). The determination signal 2810w in FIG. 22A shows an image of a portion having a bright horizontal line on a black background. The determination signals 2820w and 2830w in FIGS. 22B and 22C show images of a portion having a bright color diagonal line on a black background. The inversion determination signal (inverted luminance value Yx) obtained by inverting the determination signals (luminance values Y) 2810w, 2820w, 2830w of FIGS. 22 (A) to 22 (C) is the determination of FIGS. 20 (A) to 20 (C). It becomes the same as the signal (luminance value Y) 2810, 2820, 2830. Therefore, in the examples of FIGS. 22 (A) to 22 (C), it is determined that all the pixels of interest are line pixels.

FIG. 23 shows an example of the frequency characteristic 2900 of smoothing by the adaptive smoothing processing unit 2401. The horizontal axis shows the spatial frequency characteristics, and the vertical axis shows the corresponding frequency response. The higher the frequency band, the smaller the frequency response, and there is no response above a certain spatial frequency (2902). An example of performing halftone dot character determination including processing by the adaptive smoothing processing unit 2401 having such smoothing frequency specification will be described with reference to FIG. 24.

FIG. 24 is a diagram showing an example of halftone dot character determination by the halftone dot character determination unit 1005. Image 3000 of FIG. 24 (A) is a part of a halftone dot image extracted. The number of output lines of this halftone dot is high, and in terms of the frequency characteristic of the filter shown in FIG. 23, it is a halftone dot having a characteristic that the spatial frequency is at the position of 2903. Therefore, when the halftone dot image 3000 is filtered by the filter having the spatial frequency characteristic of FIG. 23, the periodic structure of the halftone dots disappears and a smoothed image 3010 is obtained.

A case where there are dark-colored characters in halftone dots having the same number of lines will be described with reference to FIG. 24 (B). Dark color (for example, black) characters are printed in the halftone dot image 3020, and when this image is processed by the adaptive smoothing processing unit 2401, a smoothed image 3030 is obtained. The halftone dot portion is smoothed and the periodic structure of the halftone dot disappears, the smoothing of the character portion is excluded by the adaptive processing, and the character area 3031 remains clearly. When this image is edge-enhanced by the edge-enhancing portion 2402, the image 3040 of FIG. 24 (C) is obtained. In the image 3040, the edge of the character (specifically, the edge on the character side) is emphasized. When the edge-enhanced image is subjected to the threshold value determination process by the threshold value determination unit 2403, the halftone dot character signal 3050 is obtained. The black part is the area determined as a character in halftone dots. In the embodiment, since thin characters are shown as an example, the entire characters are extracted as halftone dot characters. Although not shown, when the character size becomes large, the edge portion (outline) of the character is extracted instead of the entire character.

A case where brightly colored characters are within the halftone dots having the same number of lines as the example of FIG. 24 (A) will be described with reference to FIG. Bright color (for example, white) characters are printed in the halftone dot image 3020w, and when this image is processed by the adaptive smoothing processing unit 2401, a smoothed image 3030w is obtained. The halftone dot portion is smoothed and the periodic structure of the halftone dot disappears, the smoothing of the character portion is excluded by the adaptive processing, and the character area 3031w remains clearly. When this image is edge-enhanced by the edge-enhancing portion 2402, the image 3040w of FIG. 25 (B) is obtained. In the image 3040w, the edge of the character (specifically, the edge on the halftone dot side) is emphasized. When the edge-enhanced image is subjected to the threshold value determination process by the threshold value determination unit 2403, the halftone dot character signal 3050w is obtained. The black part is the area determined as a character in halftone dots. When a character brighter than the smoothed halftone dot region is arranged in the halftone dot, the edge portion on the halftone dot region side is extracted as the edge portion representing the outline of the character.

A-3-4. Explanation of Attribute Flag Generation Unit 1006 The attribute flag generation unit 1006 (FIG. 2) includes a character determination signal input from the character determination unit 1003, a halftone dot determination signal input from the halftone dot determination unit 1004, and characters in the halftone dots. An attribute flag is generated for each pixel based on the halftone dot character determination signal input from the determination unit 1005. The attribute flag to be generated is determined as follows.
(1) When the halftone dot determination signal is "1", the character determination signal is "0", and the halftone dot character determination signal is "0", the attribute flag is "halftone dot". The halftone dot flag 1008 becomes "1", and the halftone dot flag 1007 and the halftone dot in-halftone flag 1009 become "0".
(2) When the halftone dot determination signal is "0" and the character determination signal is "1", the attribute flag is determined to be a value indicating "character", and the character flag 1007 is "1". The halftone dot flag 1008 and the halftone dot in-character flag 1009 are set to "0".
(3) When the halftone dot determination signal is "1" and the halftone dot character determination signal is "1", the attribute flag is determined to be a value indicating "halftone dot character".
(4) In cases other than the above, the attribute flag is determined to be a value indicating "natural image, photographic image, gradation image", and the character flag 1007, the halftone dot flag 1008, and the halftone dot in-character flag 1009 are all ". It becomes "0".
As described above, since there are four types of attribute flags as described above, the attribute flags in this embodiment are composed of 2 bits per pixel.

Since flag data indicating the attribute flag for each pixel is generated in this way, various images such as an edge enhancement amount, a color reproduction method, and an image formation method can be used according to the attribute for each pixel by using the flag data. The processing method can be controlled.

A-3-5. Explanation of printing process Based on the above, a specific printing process will be described. As described above, the processed data generated from the scan data by the second input processing unit 104 (FIG. 1) and the flag data generated by the area separation processing unit 103 are compressed and stored in the main memory 113. To. What is described here is a printing process executed using the compressed processed image data and the compressed flag data.

The data decoding unit 109 reads the compressed processed image data and the compressed flag data stored in the main memory 113 at the timing when the print execution unit 140 becomes printable, and performs the decoding process. The decoded processed image data is stored in the second image memory 116, and the decoded flag data is stored in the second flag memory 115.

The output processing unit 110 generates print data based on the processed image data stored in the second image memory 116 and the flag data stored in the second flag memory 115, and outputs the print data to the print execution unit 140. To do.

FIG. 26 is a block diagram showing the configuration of the output processing unit 110. When the processed image data and the flag data of a preset amount of data that can be printed are stored in the second image memory 116 and the second flag memory 115, the processed image data and the flag data are output to the output processing unit. Transferred to 110.

The processed image data (RGB image data) transferred from the second image memory 114 is converted into CMYK image data by the RGB → CMYK conversion units 601 and 602. The CMYK image data is a color system containing color components corresponding to the color materials used for printing, and in this embodiment, C (cyan), M (magenta), Y (yellow), and K (black) components are used. It is image data indicating the color of each pixel by the color value (also called the CMYK value) of the included CMYK color system. The difference between the RGB → CMYK conversion units 601 and 602 is that the former performs conversion for character images and the latter performs conversion for photographic images and halftone dots.

Usually, the color of the characters printed in the original is black, white, or at most several colors. Therefore, in the embodiment, the RGB → YMCK conversion unit 601 converts to the most approximate color among the predefined color (C, M, Y, K) patterns. For example, when R≈G≈B≈0, it may be determined that the pixel of interest is black, so the pattern is converted to C = M = Y = 0 and K = 255. In the case of R≈G≈B≈255, it may be determined that the pixel of interest is white, so the pattern is converted to C = M = Y = K = 0. When the input R, G, and B are represented by 8 bits, the RGB → YMCK conversion unit 601 inputs each upper number of bits (about 2 bits may be sufficient) and CMYK (8 bits each). This is done using a lookup table (LUT) that outputs the data of.

The RGB → YMCK conversion unit 602 converts RGB to YMCK with high accuracy. This conversion is performed, for example, by a matrix operation. Alternatively, it is performed using a total of 24-bit address input of RGB and a 32-bit output LUT of YMCK.

The synthesis unit 603 synthesizes the CMYK image data output from the two conversion units 601 and 602 based on the flag data transferred from the second flag memory 115. Specifically, when the attribute flag of the pixel of interest included in the flag data indicates "character", the CMYK value of the pixel of interest output from the RGB → CMYK conversion unit 601 is selected and output. When the attribute flag of the pixel of interest indicates "natural image" or "halftone dot", the CMYK value of the pixel of interest output from the RGB → CMYK conversion unit 602 is selected and output. Then, when the attribute flag of the pixel of interest indicates "characters in halftone dots", a value obtained by synthesizing two CMYK values output from the two conversion units 601 and 602 according to a predetermined weight ( For example, the average value) is generated and output.

The signal indicating the CMYK value of each pixel output from the synthesis unit 603 is supplied to the filter processing units 604 to 606. These filter processing units 604 to 606 have buffers for several lines inside and perform two-dimensional filter processing. The difference between the filtering units 604 to 606 is that the coefficients that determine the degree of edge enhancement in the filtering processing are different.

The filter processing unit 604 performs a filter process suitable for "characters". The filter processing unit 605 performs filter processing suitable for "characters in halftone dots". The filter processing unit 606 performs filter processing suitable for "photographs" or "halftone dots". The degree of edge enhancement of each filter processing unit is in the order of filter processing unit 604> filter processing unit 605> filter processing unit 606. However, the degree of edge enhancement is only an example, and is not necessarily limited to this.

In the above, it can be said that the strength of the smoothing process is in the order of filter processing unit 604 <filter processing unit 605 <filter processing unit 606.

The selector 607 selects and outputs the processed CMYK value output from the filter processing unit 604 when the attribute flag of the pixel of interest indicates “character”. The selector 607 selects and outputs the processed CMYK value output from the filter processing unit 605 when the attribute flag of the pixel of interest indicates "characters in halftone dots". The selector 607 selects and outputs the processed CMYK value output from the filter processing unit 606 when the attribute flag of the pixel of interest indicates “photograph” or “halftone dot”.

The processed CMYK values output from the selector 607 are input to the gamma correction units 608 and 610. The gamma correction unit 608 makes corrections suitable for "characters" and "characters in halftone dots", and the gamma correction unit 610 makes corrections suitable for "halftone dots" and "photographic images".

The corrected CMYK value output from the gamma correction unit 608 is input to the error diffusion processing unit 609. The error diffusion processing unit 609 converts the input CMYK value into a dot value indicating a dot formation state by halftone processing according to the error diffusion method, and outputs the dot value. In the case of characters, it is desirable that the dots generated during printing are difficult to disperse, so it is preferable to use the error diffusion method for the halftone processing.

The corrected CMYK value output from the gamma correction unit 610 is input to the dither processing unit 611. The dither processing unit 611 converts the input CMYK value into a dot value indicating a dot formation state by halftone processing according to a dither method using a dither matrix, and outputs the dot value. In the case of photographic images and halftone dots, gradation is important, so it is preferable to use the dither method for halftone processing.

When the attribute flag of the pixel of interest indicates "character" or "character in halftone dots", the selector 612 selects a dot value output from the error diffusion processing unit 609 and outputs it to the print execution unit 140. Further, when the attribute flag of the pixel of interest indicates "photograph" or "halftone dot", the selector 612 selects the dot value output from the dither processing unit 611 and outputs it to the print execution unit 140.

As described above, by appropriately extracting the areas of characters, halftone dots, and characters within the halftone dots, it is possible to perform image processing according to the attributes. Therefore, it is possible to reproduce the characters clearly and the photograph smoothly. In particular, in a document containing halftone dots, it is possible to distinguish between halftone dots and characters and smooth the halftone dots without performing smoothing processing on the characters, so that suitable moire removal is possible. As a result, it is possible to print an image with high gradation by performing smoothing processing on the photograph in the document including halftone dots, removing moire, and then performing dither processing. In addition, clear and easy-to-read characters can be printed on the characters in the document including halftone dots by performing edge enhancement processing and then performing error diffusion processing.

Further, according to the first embodiment described above, the luminance data acquisition unit 1002 (FIG. 2) acquires the luminance image data indicating the luminance image by using the scan data. The first line determination unit 2503a of the adaptive smoothing processing unit 2401 (FIGS. 16 and 17) determines whether or not a plurality of pixels including the pixel of interest in the luminance image satisfy the determination conditions (1) to (6). To judge. The inversion processing unit 2507 uses the luminance image data to generate the inversion luminance image data indicating the inversion luminance image. As described above, the inverted luminance image includes a plurality of inverted luminance values Yx corresponding to the luminance values Y of the plurality of pixels included in the luminance image data. The second line determination unit 2503b uses the luminance image data (inverted luminance value Yx) to determine whether or not a plurality of pixels including the pixel of interest in the inverted luminance image satisfy the above-mentioned determination conditions (1) to (6). To judge. The adaptive smoothing processing unit 2401 executes a smoothing process for smoothing the luminance image on the luminance image data (luminance value Y) to generate smoothing data.

As described above, in the smoothed luminance image output from the adaptive smoothing processing unit 2401, the value of the pixel corresponding to the pixel in the luminance image determined to be the line pixel by the first line determination unit 2503a. Is a value that has not been smoothed by the smoothing processing unit 2502. In the smoothed luminance image, the value of the pixel corresponding to the pixel in the inverted luminance image determined to be the line pixel by the second line determination unit 2503b is not smoothed by the smoothing processing unit 2502. It is a value. In a smoothed brightness image, in a brightness image or an inverted brightness image that is not determined to be a line pixel by the first line determination unit 2503a and is not determined to be a line pixel by the second line determination unit 2503b. The value of the pixel corresponding to the pixel of is the value smoothed by the smoothing processing unit 2502.

In other words, among the M pixels (M is an integer of 2 or more) in the smoothed luminance image, a plurality of pixels in the luminance image satisfying the judgment conditions (1) to (3) or (4) to (6). N1 (N1 is an integer less than M) corresponding to at least one of the pixel and the plurality of pixels in the inverted luminance image satisfying the determination conditions (1) to (3) or (4) to (6). ) Pixels are not smoothed. Among the M pixels, it corresponds to a plurality of pixels in the luminance image that do not satisfy any of the determination conditions (1) to (3) and (4) to (6), and the determination conditions (1) to (1) to N2 pixels (N2 is an integer satisfying N1 + N2 = M) corresponding to the plurality of pixels in the inverted luminance image that do not satisfy any of (3) and (4) to (6) are smoothed. Then, the edge enhancement unit 2402 and the threshold value determination unit 2403 of the halftone dot character determination unit 1005 identify a plurality of edge pixels indicating edges by using the smoothing data.

As a result, both the low-luminance region and the high-luminance region can be judged by using the above-mentioned judgment conditions (1) to (6). Therefore, when identifying edge pixels using smoothed data, pixels representing the edges of characters represented by bright colors in a relatively low-brightness (ie, dark) background and relatively high-brightness (ie) pixels. That is, both pixels representing the edges of characters represented by dark colors in the (bright) background can be appropriately identified. Further, since the same hardware circuit can be used for the first line determination unit 2503a and the second line determination unit 2503b, the number of types of parts of the adaptive smoothing processing unit 2401 and the development load, and eventually the control unit 120 and The number of types of parts and the development load of the multifunction device 100 can be reduced.

Normally, characters are often represented in a dark color on a light background, and characters are rarely represented in a light color on a dark background. However, when the user evaluates the quality of image processing, the image quality when the characters are represented by a light color on a dark background is the same as the image quality when the characters are represented by a dark color on a light background. It can be emphasized. Therefore, as in the present embodiment, both the edge of the character represented by the dark color in the light background and the edge of the character represented by the light color in the dark background are detected and used for image processing. As a result, high-quality image processing can be realized.

As can be seen from the above description, the first line determination unit 2503a of this embodiment is an example of the first determination unit, the second line determination unit 2503b is an example of the second determination unit, and the inversion processing unit 2507. Is an example of the image data generation unit, and the whole of the smoothing processing unit 2502 and the selector 2504 is an example of the smoothing unit.

B. Second Example:
FIG. 27 is a flowchart showing another embodiment of the process of determining whether or not the pixel of interest is a line pixel. This processing is performed by the first line determination unit 2503a and the second line determination unit 2503b of the adaptive smoothing processing unit 2401 (FIG. 17). The difference from the first embodiment is that a plurality of filters associated with lines having different thicknesses are used. In the first embodiment, as shown in FIG. 18, although the line extending directions are different among the plurality of filters (specifically, the plurality of line patterns 2600 to 2630), the line thickness is approximately the same. is there. In this case, depending on the thickness of the line included in the scanned image, an appropriate determination may not be possible in the examples of FIGS. 18 to 22. For example, the pixel of interest on a thick line segment may not be determined to be a line pixel by any of the filters shown in FIGS. 18A to 18D. Therefore, in the second embodiment, the first line determination unit 2503a and the second line determination unit 2503b use a plurality of filters associated with lines having different thicknesses.

FIG. 28 is an explanatory diagram showing an example of a plurality of filters. FIG. 28A shows a filter 2660 having a line width Wd of 1 pixel, FIG. 28B shows a filter 2670 having a line width Wd of 2 pixels, and FIG. 28C shows a line width Wd. 2680 shows a filter having 3 pixels, and FIG. 28 (D) shows a filter 2690 having a line width Wd of 4 pixels. Each of these filters 2660 to 2690 shows a line pattern for determining a vertical line, similar to the line pattern 2600 of FIG. 18 (A).

The filter 2660 of FIG. 28A includes three blocks 2662, 2663, and 2664 having 19 pixels in the vertical direction and 1 pixel in the horizontal direction. These blocks 2662, 2663, and 2664 are arranged side by side in the horizontal direction with a gap having the same width as the line width Wd. The pixel of interest 2661 is located in the center of the central block 2663.

Similarly, the filter 2670 of FIG. 28B includes three blocks 2672, 2673, 2674 of 19 pixels in length × 2 pixels in width. The filter 2680 of FIG. 28C includes three blocks 2682, 2683, 2864 having 19 pixels in the vertical direction and 3 pixels in the horizontal direction. The filter 2690 of FIG. 28 (D) includes three blocks 2692, 2693, and 2694 having 19 pixels in the vertical direction and 4 pixels in the horizontal direction. In any of the filters 2670 to 2690, the three blocks are arranged side by side with a gap having the same width as the line width Wd. The attention pixels 2671, 2681, and 2691 are arranged at the center of the central blocks 2673, 2683, and 2693 (when the line width Wd is an even number, the attention pixels are arranged at the pixel positions on the left side of the center of the block. Has been).

Although not shown, the plurality of available filters are, like the filters 261 to 2630 of FIGS. 18 (B) to 18 (D), a filter showing a line pattern for determining a horizontal line and two directions. Includes a filter showing two types of line patterns for determining the diagonal lines of. As each of the four types of filters in which the extending directions of the lines are different from each other, a plurality of filters having different line widths can be used. In any of the filters, the three blocks are arranged side by side in the direction perpendicular to the extending direction of the blocks with a gap having the same width as the line width. Then, the pixel of interest is arranged at the center of the central block.

The first line determination unit 2503a (FIG. 17) and the second line determination unit 2503b use each filter to determine whether or not the pixel of interest is a line pixel, as in the case of using the filters 2600 to 2630 of FIG. To judge. The first line determination unit 2503a and the second line determination unit 2503b apply the above conditions (1) to (3) and conditions (4) to (6) to three blocks of each filter (for example, FIG. 28). By applying it to the three blocks 2662, 2663, 2664) of the filter 2660 of the above, it is evaluated and it is determined whether or not the pixel of interest is a line pixel. The threshold value 1 and the threshold value 2 of each condition may be experimentally determined in advance so that an appropriate judgment can be made.

The first line determination unit 2503a (FIG. 17) and the second line determination unit 2503b determine whether or not the pixel of interest is a line pixel according to the procedure of FIG. 27. In the example of FIG. 27, the first line determination unit 2503a and the second line determination unit 2503b cooperate to output a line switching signal. In the figure, the process surrounded by the frame with the reference numeral 2503a indicates the process of the first line determination unit 2503a, and the process surrounded by the frame with the reference numeral 2503b is the process of the second line determination unit 2503b. Shown. S190 and S195 can be executed by either the first line determination unit 2503a and the second line determination unit 2503b.

In S100, the first line determination unit 2503a initializes the line switching flag to off. In S105, the first line determination unit 2503a initializes the current line width Wd to the minimum value (here, 1) of the line width Wd of the available filter. In S110, the first line determination unit 2503a selects a filter associated with the current line width Wd. As described above, in the present embodiment, one line width Wd is associated with four filters having different lines extending directions. In S110, four filters are selected. In S115, the first line determination unit 2503a applies the four filters selected in S110 to the luminance value Y of the pixels in the filter, and determines whether or not the determination condition is satisfied for each filter. It is determined whether or not the pixel of interest is a line pixel. In S120, the first line determination unit 2503a determines whether or not the pixel of interest is determined to be a line pixel by at least one of the four filters.

When it is determined by at least one filter that the pixel of interest is a line pixel (S120: Yes), in S190, the first line determination unit 2503a sets the line switching flag to ON. In S195, the first line determination unit 2503a outputs a line switching signal (here, the line switching signal of “1”) associated with the line switching flag to the selector 2504. Then, the process of FIG. 27 ends.

If it is not determined that the pixel of interest is a line pixel by using any of the four filters (S120: No), in S125, the first line determination unit 2503a is of all available line widths Wd. Determine if the process is complete. In the example of FIG. 27, it is determined whether or not the current line width Wd is equal to or greater than the maximum value WdMax of the line width Wd of the available filter. In this embodiment, as described with reference to FIG. 28, the maximum value WdMax is 4.

When the unprocessed line width Wd remains (S125: No), in S130, the first line determination unit 2503a updates the current line width Wd to a line width Wd one step larger (in this embodiment, the line width Wd is one step larger). 1 is added to the line width Wd). Then, the first line determination unit 2503a shifts to S110 and executes the processing of the updated line width Wd.

When the processing of all line widths Wd is completed (S125: Yes), the processing shifts to S155.

In S155, the second line determination unit 2503b initializes the current line width Wd to the initial value Wdiw for bright lines. The initial value Wdiw for the bright line is set to a value larger than the initial value for the dark line (here, 1). The second line determination unit 2503b makes a determination by using a filter having a line width Wd equal to or more than the initial value Wdiw without using a filter having a line width Wd less than the initial value Wdiw for the bright line. The reason for this is as follows. When the width of a bright color line is narrow, the thin line is likely to be crushed in the printed image due to bleeding or misalignment of the coloring material representing the dark background around the line. When a thin line is crushed, the visibility of the line is lowered, so that the effect of improving the image quality of the image processing for the halftone dot characters is reduced. On the other hand, when the width of the dark color line is narrow, the line can be easily visually recognized even when the color material representing the dark color line is blurred or misaligned in the printed image. Therefore, the effect of improving the image quality of the image processing for the characters in halftone dots is high. As described above, the minimum line width Wd of the filter used in the processing for dark lines (here, 1) is smaller than the minimum line width Wd of the filter used in the processing for bright lines.

In S160, the second line determination unit 2503b selects a filter associated with the current line width Wd. S160 is performed in the same manner as S110. In S165, the second line determination unit 2503b applies the four filters selected in S160 to the inverted luminance value Yx of the pixels in the filter, and determines whether or not the determination condition is satisfied for each filter. , Determine whether the pixel of interest is a line pixel. In S170, the second line determination unit 2503b determines whether or not the pixel of interest is determined to be a line pixel by at least one of the four filters.

When it is determined by at least one filter that the pixel of interest is a line pixel (S170: Yes), in S190, the second line determination unit 2503b sets the line switching flag to ON. In S195, the second line determination unit 2503b outputs the line switching signal (here, the line switching signal of “1”) associated with the line switching flag to the selector 2504. Then, the process of FIG. 27 ends.

If it is not determined that the pixel of interest is a line pixel by using any of the four filters (S170: No), in S175, the second line determination unit 2503b processes all available line widths Wd. Determine if it is finished. Specifically, it is determined whether or not the current line width Wd is equal to or greater than the maximum value WdMax of the line width Wd of the available filter.

When the unprocessed line width Wd remains (S175: No), in S180, the second line determination unit 2503b updates the current line width Wd to a line width Wd one step larger (in this embodiment, the line width Wd is one step larger). 1 is added to the line width Wd). Then, the second line determination unit 2503b shifts to S160 and executes the processing of the updated line width Wd.

When the processing of all the line widths Wd is completed (S175: Yes), in S195, the second line determination unit 2503b is the line switching signal associated with the line switching flag (here, the line switching signal of "0"). ) Is output to the selector 2504. Then, the second line determination unit 2503b ends the process of FIG. 27.

In this embodiment, the selector 2504 (FIG. 17) receives the line switching signal output in S195 from either the first line determination unit 2503a or the second line determination unit 2503b. Then, the selector 2504 pays attention when the line switching signal is "1", that is, when the first line determination unit 2503a determines that the pixel of interest is a line pixel and when the second line determination unit 2503b determines that the pixel of interest is a line pixel. When it is determined that the pixel is a line pixel, and when it is determined, the determination signal 2501 which is not filtered is output. The selector 2504 is a smoothing signal when the line switching signal is "0", that is, when both the first line determination unit 2503a and the second line determination unit 2503b determine that the pixel of interest is not a line pixel. Is output.

FIG. 29 is an explanatory diagram of a process for determining an initial value Wdiw (that is, an available filter) for a bright line. FIG. 29A shows a flowchart of the determination process. In S200, test pattern data corresponding to each of a plurality of filters having different line widths Wd is generated. 29 (B) to 29 (E) are explanatory views showing an example of a test pattern represented by the test pattern data. 29 (B) to 29 (E) show test patterns TP1, TP2, TP3, and TP4 for Wd = 1, 2, 3, and 4, respectively. Each test pattern TP1 to TP4 represents a black base BG and white vertical lines WL1 to WL4, respectively. The white vertical lines WL1 to WL4 are data representing white vertical lines having a corresponding line width Wd. For example, the white vertical line WL1 of the test pattern TP1 for Wd = 1 is represented by data representing a white vertical line having a line width of 1. Any method can be adopted as the method for generating the test pattern data. In this embodiment, a computer (not shown) generates test pattern data according to a program.

In S210, the control unit 120 of the multifunction device 100 causes the print execution unit 140 to print the test patterns TP1 to TP4 using the test pattern data. In S220, the user determines whether or not the white line can be identified by visually observing the printed test patterns TP1 to TP4. As described above, when the line width of the printed white line is small, the white line may be crushed due to bleeding of the coloring material or the like. If the thin white line is crushed, the user cannot identify the white line. Then, the user identifies the thinnest white line among the identifiable white lines. The line width Wd associated with the specified white line is called the minimum width Wmin.

In S230, the initial value Wdiw for bright lines is set to the minimum width Wmin. The data representing the set minimum width Wmin is incorporated in the second line determination unit 2503b (FIG. 17) (for example, the data representing the minimum width Wmin is written in the non-volatile memory of the second line determination unit 2503b (not shown). ). Then, the process of FIG. 29 (A) is completed. As a result, the second line determination unit 2503b can appropriately detect pixels of bright color lines that can be identified when printed.

As described above, in the second embodiment, the first line determination unit 2503a and the second line determination unit 2503b are filters for detecting pixels representing lines, and are associated with lines having different thicknesses. It is judged whether or not the judgment condition is satisfied by using the obtained plurality of filters. Therefore, pixels representing the edges of characters represented by lines of various thicknesses can be appropriately detected.

Further, the initial value Wdiw of the line width Wd for the bright line is larger than the initial value (here, 1) of the line width Wd for the dark line. Therefore, the total number P of filters that can be used by the first line determination unit 2503a is larger than the total number Q of filters that can be used by the second line determination unit 2503b (in this embodiment, the total number P = 16 (line width Wd). The total number of 4 × the number of types in the direction of the line 4), the total number Q is 1 or more, and an integer different from P). As a result, the edges of thin characters represented by continuous lines of low-luminance pixels can be appropriately detected. In addition, the edge of a character represented by a continuous line of high-luminance pixels can be appropriately detected.

Further, the line width Wd (here, 1) of the thinnest line among the plurality of lines associated with the plurality of filters used by the first line determination unit 2503a is a plurality of lines used by the second line determination unit 2503b. It is thinner than the line width Wdiw of the thinnest line among the plurality of lines associated with the filter. Therefore, the edge of a character represented by a continuous thin line of low-luminance pixels can be appropriately detected.

Further, the area separation processing unit 103 (FIG. 1), the second input processing unit 104, and the output processing unit 110 combine the input image data acquired by the first input processing unit 102 with the halftone dots of the area separation processing unit 103. Print data, which is image data for printing, is generated by performing image processing using the edge pixels detected by the character determination unit 1005 (FIG. 16). Then, the output processing unit 110 supplies the generated print data to the print execution unit 140. Here, as described with reference to FIG. 29 (A), the line width Wdiw of the thinnest line among the plurality of types of lines associated with the plurality of filters for bright lines is the color used by the print execution unit 140. It is determined in advance based on the identification of bleeding of the material. Therefore, it is possible to detect the edge of a character represented by a line having a thickness suitable for the bleeding characteristic of the color material used by the print execution unit 140.

C. Modification example:
(1) FIG. 30 is a block diagram showing a configuration of a region separation processing unit 103B of a modified example. In the area separation processing unit 103 (FIG. 2) of the first embodiment, the luminance data acquisition unit 1002 of FIG. 2 generates a luminance value Y from the RGB values of each pixel of the scan data, and the inversion processing unit of FIG. 17 2507 generates the inverted luminance value Yx by inverting the luminance value Y.

On the other hand, in the area separation processing unit 103B of this modification, in addition to the components of the area separation processing unit 103 of FIG. 2, the inversion processing unit 1010B and the luminance data acquisition unit different from the luminance data acquisition unit 1002 It is equipped with 1002B. The inversion processing unit 1010B inverts the input signal 1001, that is, a plurality of component values (R value, G value, B value) included in the RGB values of each pixel of the scan data, and generates an inverted RGB value. To do. That is, the inversion processing unit 1010B generates inverted RGB image data including the inverted RGB values. Assuming that the RGB values before inversion are (Rin, Gin, Bin), the inverted RGB values (Rout, Gout, Bout) are represented by the following equations (2) to (4).

Rout = Rmax-Rin ... (2)
Gout = Gmax-Gin ... (3)
Bout = Bmax-Bin ... (4)

Here, Rmax, Gmax, and Bmax are the maximum values that the R value, G value, and B value can take, respectively, and in this embodiment, Rmax = Gmax = Bmax = 255. The signal indicating the inverted RGB value is input to the luminance data acquisition unit 1002B.

The luminance data acquisition unit 1002B calculates a signal indicating a luminance value, which is the degree of brightness of the color indicated by the inverted RGB value, as an inverted luminance value YxB, based on the inverted RGB value. It is generated as a pixel-based determination signal for attribute determination. The luminance value is acquired by using a plurality of component values (R value, G value, B value) included in the RGB value. The signal indicating the inverted luminance value YxB is input to the halftone dot character determination unit 1005.

In this modification, in the halftone dot character determination unit 1005 of FIG. 17, the inversion processing unit 2507 is omitted, and the inversion brightness value YxB from the luminance data acquisition unit 1002B of FIG. 30 is input to the second line determination unit 2503b. Will be done.

As can be seen from the above description, in the first embodiment and the second embodiment, the brightness image data generated by the brightness data acquisition unit 1002 of FIG. 2 is an example of the first image data, and is shown in FIG. The inverted brightness image data generated by the inversion processing unit 2507 is an example of the second image data. In this modification, the scan data (RGB image data) is an example of the first image data, and the inverted RGB image data generated by the inversion processing unit 1010B of FIG. 30 is an example of the second image data. .. Then, in the first embodiment and the second embodiment, the image data to be smoothed by the adaptive smoothing processing unit 2401 is the first image data itself (that is, the luminance image data). On the other hand, in this modification, the target image data smoothed by the adaptive smoothing processing unit 2401 is the brightness image data generated by using the first image data (that is, RGB image data). Is. In this way, the image data to be smoothed by the adaptive smoothing processing unit 2401 is generated by using the image data based on the first image data (the first image data itself or the first image data). Image data to be generated) will do.

In the first embodiment and the second embodiment, the image data to be smoothed may be inverted luminance image data instead of the luminance image data.

(2) Judgment conditions for the first line determination unit 2503a and the second line determination unit 2503b (FIG. 17) to determine that the pixel of interest is a line pixel, that is, a plurality of pixels of interest having a brightness less than the reference. The conditions indicating that the pixels are in the continuous low-luminance region are not limited to the above-mentioned conditions (1) to (3) and conditions (4) to (6), and may be various conditions. For example, when both of the following conditions (A1) and (B1) are satisfied, or when both of the conditions (A1) and (C1) are satisfied, it may be determined that the pixel of interest is a line pixel. ..
(A1) The brightness of the plurality of pixels in the block 2603 is equal to or less than a predetermined threshold value TH1 (for example, 100). (B2) The brightness of the plurality of pixels in the block 2602 is a predetermined threshold value. TH2 (eg, 150) or higher (C2) The brightness of the plurality of pixels in the block 2604 is TH2 (eg, 150) or higher, respectively.

Further, the brightness of the pixel of interest is equal to or less than a predetermined threshold value TH3 (for example, 50), and a predetermined number (for example, 5) continuous from the pixel of interest in a predetermined direction (for example, up / down / left / right and diagonal directions). When the brightness of the pixel is a predetermined threshold value TH3, the pixel of interest may be determined to be a line pixel.

As described above, the determination condition is determined based on the brightness (for example, the average brightness of the surrounding pixels) of the pixels around the pixel of interest (for example, block 2602 and a plurality of pixels in the block 2604). It may be a condition that is determined based on a predetermined absolute value, such as the threshold value TH3 of the modified example.

(3) In the first embodiment and the second embodiment, as a determination condition, a condition indicating that the pixel of interest is in a continuous low-luminance region of a plurality of pixels having a brightness less than the reference is used. .. Instead of this, as a determination condition, a condition indicating that the pixel of interest is in a continuous high-luminance region of a plurality of pixels having a brightness equal to or higher than the reference may be used. For example, when the following conditions (1), (2), and (7) are all satisfied, or when the following conditions (4), (5), and (8) are all satisfied, the pixel of interest is a line pixel. It may be judged.
Condition (1) MAX (2602) -MIN (2602) ≤ Threshold 1
Condition (2) MAX (2603) -MIN (2603) ≤ Threshold 1
Condition (7) ALL (2603) ≧ ALL (2602) + Threshold 2
Condition (4) MAX (2604) -MIN (2604) ≤ Threshold 1
Condition (5) MAX (2603) -MIN (2603) ≤ Threshold 1
Condition (8) ALL (2603) ≧ ALL (2604) + Threshold 2
The above conditions (1), (2), (4), and (5) are the same as the conditions (1), (2), (4), and (5) described in the first embodiment. Condition (7) compares the sum of the pixel values in the block 2602 with the sum of the pixel values in the pixel block 2603, and the pixel block 2603 is relative to the pixel block 2602 in terms of pixel values. It is a condition to evaluate that it is high. Condition (8) compares the sum of the pixel values in the block 2604 with the sum of the pixel values in the pixel block 2603, and the pixel block 2603 is relative to the pixel block 2604 in terms of pixel values. It is a condition to evaluate that it is high.

When this condition is adopted, the determination by the first line determination unit 2503a that the pixel of interest is a line pixel means that the pixel of interest is determined to be a line pixel on a bright line. When the second line determination unit 2503b determines that the pixel of interest is a line pixel, it means that the pixel of interest is determined to be a line pixel on a dark line. Even in this case, as a result, the first line determination unit 2503a and the second line determination unit 2503b either indicate that the pixel of interest is a line pixel on a dark line, a line pixel on a bright line, or It will be judged whether it is also a line pixel.

The conditions for indicating that the pixel of interest is in the continuous high-luminance region of a plurality of pixels having a brightness equal to or higher than the reference value are not limited to the above conditions, and are various as in the modified example (1), for example. It can be transformed. Generally, the determination condition used by the first line determination unit 2503a and the second line determination unit 2503b is that the pixel of interest is in a low-luminance region in which a plurality of pixels having a brightness less than the reference are continuous. One of the first type of condition indicating that the pixel of interest is in a continuous high-luminance region of a plurality of pixels having a brightness equal to or higher than the reference value. preferable.

(4) One or more filters that can be used by the first line determination unit 2503a and one or more filters that can be used by the second line determination unit 2503b are replaced with the filters described in FIGS. 18 and 27 to 29. It may be various other filters. For example, the spacing of the three blocks (eg, the three blocks 2662, 2663, 2664 in FIG. 28 (A)) contained in one filter may be different from the width of each block. Generally, as a filter, it is possible to detect various filters capable of detecting pixels representing a line of a specific thickness, that is, pixels included in a region representing a line of a specific thickness. Various filters can be adopted.

Further, in the second embodiment, the total number Q of the filters that can be used by the second line determination unit 2503b may be the same as the total number P of the filters that can be used by the first line determination unit 2503a. It may be any integer different from the total number P. Here, P> Q may be satisfied, or P <Q may be satisfied.

Further, the minimum line width of one or more filters for dark lines that can be used by the first line determination unit 2503a is larger than the minimum line width of one or more filters for bright lines that can be used by the second line determination unit 2503b. May be thick. Further, the minimum line width of one or more filters that can be used by the second line determination unit 2503b may be determined independently of the bleeding characteristic of the coloring material.

Further, as a filter, it is for determining whether or not there is a difference in luminance value between a linear region extending in a specific direction and at least one of two regions sandwiching the linear region. , Various filters may be adopted.

The first line determination unit 2503a may determine whether or not the pixel of interest is included in the specific region of the first type without using such a filter. For example, the first line determination unit 2503a identifies a region in which pixels whose luminance value is less than a predetermined first threshold value is continuous by analyzing the luminance image data, and uses the identified region as a first type specific region. It may be adopted. Similarly, the second line determination unit 2503b may determine whether or not the pixel of interest is included in the specific region of the second type without using such a filter. For example, the second line determination unit 2503b identifies a region in which pixels whose luminance value exceeds a predetermined second threshold value is continuous by analyzing the luminance image data, and adopts the identified region as a second type specific region. (Here, the second threshold value is equal to or higher than the first threshold value).

(5) In each of the above embodiments, the processed image data is used by the print execution unit 140 to print the processed image (FIG. 26). Not limited to this, the processed image data may be used to display the processed image on a display unit such as a liquid crystal display.

(6) In each of the above embodiments, the input signal 1001 (FIG. 1) is an RGB value. Instead of this, color values of other color systems may be used. For example, the value of each pixel of the scan data may be input to the area separation processing unit 103 as an input signal 1001 after being converted into a color value of the CMY color system.

(7) Specific processing executed by each unit included in the area separation processing unit 103 of each of the above embodiments, for example, the character determination unit 1003, the halftone dot determination unit 1004, and the halftone dot in-character determination unit 1005, is an example. , Will be changed accordingly. For example, the peripheral range of vertical 3 pixels × horizontal 3 pixels used by the area integration unit 1105 and 1106 in FIG. 3 is a range of other sizes, for example, a range of vertical 3 pixels × horizontal 5 pixels or vertical 5 pixels × horizontal 5 pixels. It may be. Further, the integration processing unit 1209 of FIG. 12 uses three types of integration ranges, and the size and number of types of these integration ranges can be appropriately changed. Further, the threshold value for the threshold value determination unit 1211 to determine the integration result is appropriately adjusted according to the size of the integration range to be used and the like. When the comprehensive determination unit 1213 of FIG. 12 uses a plurality of determination results output for each integration range by these threshold value determination units 1211 to generate a halftone dot determination signal, for example, a logical sum or a logical product. How to combine the logical operations of can be changed as appropriate.

(8) The process (FIG. 26) in which the output processing unit 110 generates print data is an example and can be changed as appropriate. For example, the output processing unit 110 has shown an example of adopting an error diffusion method or a dither method as halftone processing, but the present invention is not limited to this. For example, when only the error diffusion method is used, the error diffusion matrix size of the former is reduced and the error diffusion matrix size of the latter is increased for characters (including characters in halftone dots) and photographs (including halftone dots). Is preferable. Further, when only the dither processing is used, different dither matrix patterns may be adopted for the characters and the photograph. Further, as the halftone processing method, other methods may be adopted.

(9) In the above embodiment, the input image data is scan data, but is not limited to this. The input image data may be captured image data generated by optically photographing a document such as a printed matter with a digital camera provided with a two-dimensional image sensor. Further, the target image data may be image data generated by using an application program such as a word processor for creating a document, an illustration, or the like.

(10) The edge pixels detected by the edge enhancement unit 2402 and the threshold value determination unit 2403 may be used for arbitrary processing. For example, it may be used to generate edge image data representing an edge.

(11) All or part of the processing executed by the multifunction device 100 of FIG. 1, for example, the processing executed by the area separation processing unit 103, the second input processing unit 104, and the output processing unit 110 is not limited to the multifunction device 100. , May be performed by various devices. For example, the scanner or the digital camera may execute the process executed by the area separation processing unit 103 or the second input processing unit 104 using the input image data generated by itself. Further, for example, a connected terminal device (not shown) or a server (not shown) capable of communicating with a scanner or a printer uses scan data acquired from the scanner to perform an area separation processing unit 103 or a second input processing unit 104. And the process executed by the output processing unit 110 may be executed. Then, the print data generated as a result may be supplied to the printer. Further, a plurality of computers (for example, a cloud server) capable of communicating with each other via a network partially share the processing executed by the area separation processing unit 103, the second input processing unit 104, and the output processing unit 110. , As a whole, image processing may be performed. In this case, the entire plurality of computers is an example of an image processing device.

In each of the above embodiments, all or part of the processing executed by the area separation processing unit 103, the second input processing unit 104, and the output processing unit 110 is executed by these hardware circuits, but is a CPU. It may be executed by the main processor 101. In this case, among the processes executed by the area separation processing unit 103, the second input processing unit 104, and the output processing unit 110, the program for the processing executed by the main processor 101 is included in the computer program PG. For example, in the first embodiment, the main processor 101 uses the process of generating the brightness image data executed by the area separation processing unit 103 and the brightness image data to include the pixel of interest in the specific area of the first type. A process of determining whether or not the brightness image data is used, a process of determining whether or not the pixel of interest is a line pixel using the brightness image data, and a process of generating inverted brightness image data using the brightness image data. A process of determining whether or not the pixel of interest is a line pixel using the inverted brightness image data, a process of generating smoothing data by smoothing the brightness image data using these determination results, and smoothing. The process of identifying a plurality of edge pixels using the converted data may be realized by executing the computer program PG.

In this way, in each of the above embodiments, a part of the configuration realized by the hardware may be replaced with software, and conversely, a part or all of the configuration realized by the software may be replaced with the hardware. It may be replaced.

Although the present invention has been described above based on Examples and Modifications, the above-described embodiments of the invention are for facilitating the understanding of the present invention and do not limit the present invention. The present invention can be modified and improved without departing from the spirit and claims, and the present invention includes equivalents thereof.

100 ... Complex machine, 101 ... Main processor, 102 ... First input processing unit, 103 ... Area separation processing unit, 104 ... Second input processing unit, 106 ... Interpreter, 107 ... Data compression unit, 108 ... Resolution conversion unit, 109 ... Data decoding unit, 110 ... Output processing unit, 111 ... First image memory, 112 ... First flag memory, 113 ... Main memory, 114 ... Second image memory, 115 ... Second flag memory, 116 ... Second image memory , 117 ... Non-volatile memory, 120 ... Control unit, 130 ... Read execution unit, 140 ... Print execution unit, 200 ... Composite machine, 601 ... Conversion unit, 603 ... Synthesis unit, 604 ... Filter processing unit, 604 ... Filter processing unit , 605 ... Filter processing unit, 606 ... Filter processing unit, 607 ... Selector, 608 ... Gamma correction unit, 609 ... Error diffusion processing unit, 610 ... Gamma correction unit, 611 ... Data processing unit, 612 ... Selector, 1001 ... Input signal , 1002 ... Brightness data acquisition unit, 1003 ... Character determination unit, 1004 ... Halftone dot determination unit, 1005 ... In-halftone dot character determination unit, 1006 ... Attribute flag generation unit, 1007 ... Character flag, 1008 ... Halftone dot flag, 1009 ... Halftone dot character flag 1102 ... Edge enhancement unit 1103 ... Threshold determination unit 1104 ... Threshold determination unit 1105 ... Area integration unit 1106 ... Area integration unit 1107 ... Threshold determination unit 1108 ... Threshold determination unit 1109 ... Comprehensive determination unit 1110 ... Character determination signal 1202 ... Edge enhancement unit 1203 ... Threshold determination unit 1204 ... Threshold determination unit 1205 ... Isolation amount determination unit 1206 ... Isolation amount determination unit, 1209 ... Integration processing unit, 1211 ... Threshold determination unit, 1213 ... Comprehensive determination unit, 1215 ... Halftone dot determination signal, 1302 ... Outer edge region, 1303 ... Inner edge region, 1304 ... Region, 1305 ... Region, 1306 ... Region, 1501 ... Edge boundary portion, 1502 ... Character , 1503 ... background, 1504 ... brightness image data, 1507 ... edge extraction data, 1510 ... cross section, 1601 ... halftone dot edge boundary, 1601 ... edge boundary, 1602 ... halftone dot, 1603 ... background, 1604 ... brightness image data, 1607 ... Edge extraction data, 1610 ... Cross section, 1700 ... Inner edge signal, 1710 ... Judgment pattern, 1712 ... Black pixel, 1713 ... White pixel, 1810 ... Inner edge signal, 1820 ... Inner edge signal, 1830 ... Inner edge signal, 1840 ... Inner edge signal, 2011 ... 1st integration unit, 2012 ... 2nd integration unit, 2013 ... 3rd integration unit, 2021 ... 1st judgment unit, 20 22 ... 2nd determination unit, 2023 ... 3rd determination unit, 2101 ... Attention pixel, 2102 ... Integration range, 2103 ... Integration range, 2104 ... Integration range, 2205 ... Edge, 2401 ... Adaptive smoothing processing unit, 2402 ... Edge enhancement Unit, 2403 ... Threshold determination unit, 2501 ... Judgment signal, 2502 ... Smoothing processing unit, 2503a ... First line determination unit, 2503b ... Second line determination unit, 2504 ... Selector, 2505 ... Adaptive smoothing signal, 2507 ... Inversion Processing unit, PG ... Computer program

Claims (6)

It is an image processing device
An image data acquisition unit that acquires the first image data indicating the first image, and
A first determination unit for determining whether or not a plurality of pixels including the first pixel of interest in the first image satisfy a specific type of determination condition by using the first image data. The specific type of determination condition includes the first type of condition indicating that the first attention pixel is in a continuous low brightness region of a plurality of pixels having a brightness less than the reference, and the first attention. The first determination unit, which is one of the second type conditions indicating that a plurality of pixels having a brightness equal to or higher than a reference are in a continuous high brightness region.
An image data generation unit that uses the first image data to generate second image data indicating a second image, wherein the second image data is a plurality of images included in the first image data. The image data generation unit includes a plurality of corresponding values corresponding to the values of the individual pixels, and each of the plurality of corresponding values is a value obtained by inverting the value of the corresponding pixel of the first image data. When,
Using the second image data, it is determined whether or not a plurality of pixels including the second pixel of interest in the second image satisfy the determination condition of the specific type, which is one of the conditions. Second judgment department and
A smoothing unit that generates smoothing data by executing a smoothing process for smoothing the target image indicated by the target image data on the target image data based on the first image data. among the pixels of M (M is an integer of 2 or more) in the target image, wherein a plurality of pixels of a particular species of determination satisfies said first image, the particular species of determination satisfies said first a plurality of pixels in the two images, N1 pieces corresponding to at least one of (N1 is an integer less than M) without smoothing the pixels of the not satisfy the particular species of determination conditions of the first image N2 pixels (N2 is an integer satisfying N1 + N2 = M) corresponding to the plurality of pixels in the second image and corresponding to the plurality of pixels in the second image that do not satisfy the determination condition of the specific type. The smoothing unit, which generates the smoothing data by smoothing,
Using the smoothing data, an edge specifying portion that specifies a plurality of edge pixels indicating an edge,
Equipped with a,
The first determination unit and the second determination unit are filters for detecting pixels representing lines, respectively, and are specified by using a plurality of filters associated with lines having different thicknesses. An image processing device that determines whether or not a species determination condition is met. The image processing apparatus according to claim 1.
The first-size cross section, respectively, a filter for detecting the pixels representing a line, P-number of at least one filter (P is an integer of 1 or more) associated with different thickness of a line with one another To determine whether or not the above-mentioned specific type of determination condition is satisfied,
The second determination unit is a filter for detecting pixels representing lines, and has Q pieces (Q is 1 or more and an integer different from P) associated with lines having different thicknesses. At least one of the filters is used to determine whether or not the particular type of determination condition is met.
Image processing device. The image processing apparatus according to claim 2.
The specific type of condition is the first type of condition indicating that the first pixel of interest is in a continuous low-luminance region of a plurality of pixels having a brightness less than the reference.
P> Q,
Image processing device. The image processing apparatus according to claim 3.
The width of the thinnest line among the P-type lines associated with the P filters that can be used by the first determination unit is the Q associated with the Q filters that can be used by the second determination unit. Thinner than the width of the thinnest of the types of lines,
Image processing device. The image processing apparatus according to claim 4.
An output data generation unit that generates output data, which is image data for printing, by performing image processing using the plurality of edge pixels on the input image data.
A supply unit that supplies the output data to a print execution unit that prints an image using a color material, and a supply unit.
With
The first image data is data based on the input image data, and is
The width of the thinnest line among the Q type lines associated with the Q filters that can be used by the second determination unit is determined in advance based on the bleeding characteristics of the color material used by the print execution unit. Has been,
Image processing device. It ’s a computer program
An image data acquisition function that acquires the first image data indicating the first image, and
This is a first determination function for determining whether or not a plurality of pixels including the first pixel of interest in the first image satisfy a specific type of determination condition by using the first image data. The specific type of determination condition includes the first type of condition indicating that the first attention pixel is in a continuous low brightness region of a plurality of pixels having a brightness less than the reference, and the first attention. The first determination function, which is one of the second type conditions indicating that a plurality of pixels having a brightness equal to or higher than a reference are in a continuous high brightness region.
It is an image data generation function that generates a second image data indicating a second image by using the first image data, and the second image data is a plurality of images included in the first image data. The image data generation function, which includes a plurality of corresponding values corresponding to the values of the individual pixels, and each of the plurality of corresponding values is a value obtained by inverting the value of the corresponding pixel of the first image data. When,
Using the second image data, it is determined whether or not a plurality of pixels including the second pixel of interest in the second image satisfy the determination condition of the specific type, which is one of the conditions. Second judgment function and
A smoothing function for generating smoothing data by executing a smoothing process for smoothing the target image indicated by the target image data on the target image data based on the first image data. among the pixels of M (M is an integer of 2 or more) in the target image, wherein a plurality of pixels of a particular species of determination satisfies said first image, the particular species of determination satisfies said first a plurality of pixels in the two images, N1 pieces corresponding to at least one of (N1 is an integer less than M) without smoothing the pixels of the not satisfy the particular species of determination conditions of the first image N2 pixels (N2 is an integer satisfying N1 + N2 = M) corresponding to the plurality of pixels in the second image and corresponding to the plurality of pixels in the second image that do not satisfy the determination condition of the specific type. With the smoothing function, which generates the smoothing data by smoothing,
An edge identification function that identifies a plurality of edge pixels indicating an edge using the smoothing data, and
To the computer ,
The first determination function and the second determination function are filters for detecting pixels representing lines, respectively, and are specified by using a plurality of filters associated with lines having different thicknesses. A computer program that determines whether or not a species judgment condition is met.

Images