JPH09167222A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and properly process images according to their types. SOLUTION: The image processor is provided with a PDL(page description language) buffer 108 which stores image data that are described in a page description language, a 1st rasterizer 112 which generates the raster image data based on the image data stored in the buffer 108, a 2nd rasterizer 140 which identifys the types of images shown in the raster image data based on the image data stored in the buffer 108, and an image processor 146 which processes the raster image data based on identification result of the rasterizer 140. And, the rasterizer 140 discriminates the image areas from the images. Furthermore, the means 146 turns the areas other than the images into run length codes and also turns the image areas into JPEG(joint photographic expert group) codes.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a page description language (Pa
The data (PDL data) described in ge Description Language (PDL) is received and expanded into image data,
The present invention relates to an image processing device for outputting to an image forming device.

[0002]

2. Description of the Related Art FIG. 13 shows the configuration of a conventional printer. A word processor on the host computer 102,
PDL data is created using software such as desktop publishing. The created PDL data is stored in the PDL buffer 108 of the image forming apparatus via the interface cable 104 and the external interface 106.

PDL stored in the PDL buffer 108
The data is sequentially read by the rasterizer 112, developed into raster image data, and written in the page memory 110. One page of raster image data can be written in the page memory 110. The ROM 114 stores font data and is used to convert the character code in the PDL data into bit image data. The internal bus 116 connects the external interface 106, the PDL buffer 108, the rasterizer 112, the ROM 114, and the page memory 110. Image forming apparatus 12
Reference numeral 6 is, for example, an electrophotographic printer. The image enhancing unit 124 performs high resolution processing in the main scanning direction.

FIGS. 14A and 14B show an example in which the resolution in the main scanning direction is doubled and quadrupled, respectively. As is apparent from the figure, the quality of characters and line drawings can be greatly improved by increasing the resolution. Generally, print quality can be improved by increasing the resolution and the number of gradations. However, a page memory having a large capacity is required to store an image with an increased resolution and gradation. Therefore, after rasterizing and storing the image in the page memory 110, the image emphasizing unit 124 immediately before the image forming apparatus 126 smoothes the image by pattern matching or the like to increase the resolution of the image.

Printing by an electrophotographic image forming apparatus is generally high speed and cannot be stopped midway. Therefore, the printing raster image data is read from the page memory 110 according to the synchronization signal in accordance with the printing speed of the image forming apparatus 126, and is sent to the image interface 120.

[0006]

[Problem to be solved by the invention] PD of image of one page
In L data, for example, text, line, solid,
Graphics such as gradation, images such as natural images read from a scanner, and halftone generation processing 2
Various elements such as value halftone dots are mixed. It is necessary to switch whether to perform the above-mentioned image processing or switch the image processing method according to the element of the image. For this,
It is necessary to identify the type of image.

FIG. 15 shows the flow of image data in the printer of FIG. Rasterizer 11 for PDL data
After rasterized into raster image data by 2, the image enhancement unit 124 performs image processing for high image quality. That is, the raster image data that has been developed is analyzed. The image enhancement unit 124 is an image analysis unit 136 that analyzes a raster image.
And an enhancement unit 137 that enhances the image according to the analysis result. The image enhancement unit 124 detects, for example, an edge of the raster image sent from the page memory 110 or compares it with a predetermined pattern. Smoothing and edge enhancement are performed according to the result.

However, the analysis of the raster image cannot accurately identify the predetermined area. For example, in order to perform smoothing, it is necessary to detect the edges of characters and diagrams. However, it is difficult to detect only the edge pixels of a character or a diagram, and the edge portion of the picture area or the low-tone portion of the halftone dot image is erroneously detected. Therefore, unnecessary smoothing processing is performed, and the quality of the image deteriorates. Therefore, an object of the present invention is to provide an image processing device that can solve such problems.

[0009]

In order to achieve such an object, the invention described in claim 1 is a storage means for storing PDL data described in a page description language, and a storage means for storing the PDL data. A generating means for generating an image based on the PDL data, an identifying means for identifying the type of the image based on the PDL data stored in the storage means, and a processing means for processing the image based on the type of the image. It is characterized by that.

In the image processing apparatus according to claim 1,
The identifying means may identify the image area from the image based on the PDL data, and the image processing means may run-length code the area other than the image. The image processing means may be configured so that the image area is JPEG encoded and the area other than the image is smoothed.

According to a second aspect of the present invention, in the image processing apparatus according to the first aspect, the identifying means has means for identifying an edge area from the image based on the PDL data, and the image processing means in the edge area. It is characterized in that it has means for performing processing for enhancing the contrast of an image and smoothing processing.

According to a third aspect of the present invention, in the image processing apparatus according to the first or second aspect, the generation means and the identification means each have a semiconductor device for processing PDL data, and each semiconductor device has a storage means. The PDL data stored in is accessed in parallel. Also,
According to a fourth aspect of the present invention, in the image processing apparatus according to the first aspect, the identifying means identifies an image area and an area other than the image area.

Since the image processing apparatus of the present invention analyzes image data represented by PDL, it is possible to accurately identify and process the type of image. Further, since a rasterizer that interprets PDL data and generates a raster image and a rasterizer that interprets PDL data and generate PDL analysis data are independently provided, flexibility and expandability are high.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a first configuration of an image processing apparatus of the present invention. Portions corresponding to the configuration of the printer shown in FIG. 13 are denoted by the same reference numerals, and therefore their description will be omitted. In FIG. 1, an image compression unit 122 is a JPEG (Joint Photog) which is an international standard color still image encoding system.
Raphic Erpert Group), run length encoding, etc., can be used to compress the image in multiple ways.

FIG. 2 shows the flow of PDL and image data in this embodiment. The rasterizer 112 is a PDL
Raster expansion unit 1 for generating raster image data from data
39 and an image analysis unit 136 that analyzes PDL data to extract characters, line drawing areas, and image areas. The rasterizer 112 stores the raster image data obtained by expanding the PDL data and the analysis result of the PDL data in the buffer memory 132.

FIG. 3 shows ADOB as an example of PDL.
The structure of Post Script (registered trademark) of company E is shown. PDL
Describes an image of one page by combining (1) character element, (2) graphic element, (3) image element, and the like.

Here, the character element is described by specifying the font type and size, color, coordinates, and character string.
A graphic element is described by designating a color, coordinates, a graphic such as a line or arc, and a filling method. The image element is
Scaling information according to image size and output resolution,
And describe by image data.

A method of analyzing PDL data will be described with reference to FIG. First, the image is divided into blocks of 8 × 8 pixels. Next, it is determined whether each block is a character or graphic area or an image area such as a natural image. Attributes such as characters, figures, and images, and coordinate information are described in PDL data. Therefore, it is possible to avoid erroneously identifying an image as in the case of analyzing raster image data.

The image compression unit 122 compresses the raster image data stored in the buffer memory 132 according to the analysis result of the PDL data. That is, the image area is JPEG
Areas other than images such as characters and figures are compressed by using the run length encoding method. The image compression unit 122 stores the code indicating the compressed raster image and the compression method in the code memory 134. The image compression unit 122 corresponds to “processing means” described in the claims.

By compressing the image, P of multiple pages
DL data can be efficiently output. Images can be printed with a memory smaller than the page memory 110. Especially in a color printer, the page memory 11
By omitting 0, the printer can be constructed at low cost.

In accordance with the printing speed of the image forming apparatus 126, the code data is output from the code memory 134 in accordance with the synchronizing signal and sent to the image interface 120. The image decoding unit 128 uses the image interface 120.
The image forming apparatus 126 receives code data from the image forming apparatus 126, decodes the image according to the synchronization signal, and generates a raster image.
Send to

(Embodiment 2) In Embodiment 1, whether or not the image area is analyzed and the image is compressed using the analysis result. However, raster image data may be processed by various methods other than compression. For example, the pseudo high resolution shown in FIG. 14 and the conversion of the resolution and the number of gradations for outputting by an image output device having a different resolution or the number of gradations may be performed. In order to perform these processes, it is necessary to obtain information according to the process from the PDL data.

For example, there are cases where the coordinate information of the edge portion of a character or a pattern is required, and information of a binary image area including a halftone dot area is required. In order to save the memory capacity, it is desirable to extract and store only the minimum necessary information. However, in the case of the configuration of the first embodiment, it is necessary to convert the rasterizer 112 according to the information extracted from the PDL data. Therefore, the flexibility and expandability of the system are low. Further, when the rasterizer 112 is caused to analyze the PDL data as described in the first embodiment, the rasterizer 112 becomes large in scale and the expansion speed decreases. Therefore, in the present embodiment, a rasterizer that expands PDL data and a rasterizer that determines the type of image using PDL data are provided independently.

FIG. 5 shows the configuration of the image processing apparatus in this embodiment. The same reference numerals are given to the configuration corresponding to FIG. 1 or FIG. 13, and thus the description thereof will be omitted. The rasterizer 112 expands the PDL data and stores it in the page memory 110. The rasterizer 140 analyzes the PDL data stored in the PDL buffer 108, generates PDL analysis data indicating the type of image described, and stores the PDL analysis data in the page memory 142.

Rasterizer 112 and rasterizer 1
Each 40 has a CPU and a ROM. The CPUs of the rasterizer 112 and the rasterizer 140 can independently access the PDL buffer 108 and process PDL data.

FIG. 6 shows the flow of image data in the image processing apparatus shown in FIG. The raster image stored in the page memory 110 and the PDL analysis data stored in the page memory 142 are sent to the image processing unit 110 via the image interface 120. Image processing unit 146
Processes the image received from the page memory 110 according to the PDL analysis data received from the page memory 142. The processed raster image is output by the image forming apparatus 126.

FIG. 7A shows a raster image in which the PDL data shown in FIG. 6 is expanded. The expanded image data is stored in the page memory 110. In this embodiment,
8-bit raster image data is developed for each color.

FIG. 7B shows the types of images analyzed by the rasterizer 140. As shown in the figure, each of the pixels indicates "edge portion", "image portion", or "other than edge image". Specifically, the drawing area of the image element is referred to as an "image part". Further, all pixels on which character elements of a certain point, for example, 20 points or less, are drawn are defined as “edge portion”. If a certain point is exceeded, the edge pixel of the character is set as the “edge portion” and the other pixels are set as the “non-edge image”. Also for the graphic element, the edge pixel is defined as “edge portion”, and the other pixels are defined as “other than edge image”.

The configuration of the image processing unit 146 will be described with reference to FIG. The image processing unit 146 corresponds to “processing means” described in the claims. The image processing unit 146 includes a spatial filter 200, a gradation correction unit 202, and a halftone generation unit 2.
04. Each processing unit has raster image data and PD
L analysis data is input. Each pixel is an "edge"
Processing is performed according to PDL analysis data indicating which of "image part" and "other than edge image".

The spatial filter section 200 includes the image forming apparatus 1
26 and the halftone generation unit 204 are filtered in order to correct the characteristics. The spatial filter section 200 is preset with filter coefficients suitable for the characteristics of the image, and for example, for the “image section”, a filter coefficient that does not cause moire is selected. The tone correction unit 202 also has a tone correction table that matches the image forming apparatus 126 and the halftone generation method. For example, the “edge portion” and “other than the edge image” are subjected to gradation correction so as to emphasize the contrast.

The halftone generating section 204 generates a halftone and generates a color binary image to be printed by the image forming apparatus 126. The halftone generation unit 204 switches the halftone generation method according to the image characteristics indicated by the PDL analysis data. For example, when binarizing a multi-valued image by dither processing, a large dither matrix is used in the “image part” so as to increase the number of gradations at the expense of resolution. Further, in the "edge portion", the pseudo high resolution shown in FIG. 14 is performed.

(Third Embodiment) FIG. 9 is a block diagram showing the arrangement of an image processing apparatus according to the present invention in the third embodiment.
In FIG. 9, the components corresponding to those in FIG. 1, FIG. 4 or FIG. 13 are designated by the same reference numerals, and the description thereof will be omitted. The image processing device is yellow, magenta, cyan,
One dot of each color of black is represented by a binary value.

The RAM 118 is used as a work area. In addition to fonts, multi-valued images are stored in the ROM 114.
A dither pattern for digitizing is stored. The image compression unit 122 performs run-length coding on the images of yellow, magenta, cyan, and black in accordance with the characteristics of the image. The page memory 110 includes a rasterizer 112.
The raster image generated in step S1 and encoded by the image compression unit 122 is stored.

FIG. 10 shows PDL analysis data generated by analyzing the PDL data shown in FIG. 6 by the rasterizer 140. This PDL analysis data indicates whether or not each block is the "image part". In this embodiment, the area including the drawing by the image element is referred to as an “image part”.

FIG. 11 shows a method of processing image data in this embodiment. The image compression unit 122 uses, for example, 8 based on the PDL analysis data generated by the rasterizer 140.
It is determined whether or not the "image part" is included in one block having a line as a unit. A block not including the “image part” is rungless encoded and stored in the page memory 110. The image compression unit 122 corresponds to “processing means” described in the claims.

The block including the "image part" is stored in the page memory 110 as it is as raster image data without being run-length encoded. The PDL analysis data indicating whether or not each block includes an “image part”, that is, the data indicating whether or not the image is run-length encoded, is stored in the page memory 1.
42. The image data stored in the page memory 110 and the PDL analysis data stored in the page memory 142 are sent to the image processing unit 146 via the image interface 120.

The configuration of the image processing unit 146 will be described with reference to FIG. The image processing unit 146 includes an image decoding unit 206 and an image enhancing unit 208. The image decoding unit 206 identifies whether or not the block of the image data input from the page memory 110 is run-length encoded according to the PDL analysis data input from the page memory 142. If the raster image data input from the page memory 110 is run-length encoded, the image is decoded.
The image processing unit 146 also corresponds to “processing means” described in the claims.

The image enhancement unit 208 receives the decoded raster image data and PDL analysis data. Areas other than the “image part” are output to the image forming apparatus 126 with high resolution as shown in FIGS. 14 (A) and 14 (B). The pixels of the "image part" are output to the image forming apparatus without being increased in resolution.

(Embodiment 4) In the above embodiment, spatial filtering, gradation correction, halftone generation, and image compression are performed by obtaining information indicating an edge portion, an image portion, and an area other than the edge image. It was However, for other image processing as well, by extracting information for appropriately performing the image processing from the PDL data,
The quality of image processing can be improved.

For example, due to an error in the printing position of each color of the image forming apparatus, white spots may occur at the boundary between the printing portions of each color. Therefore, for example, as shown in FIG. 7A, in a portion where a black character “Black” and a green circle overlap, green is also printed in an area in which the black character is printed to prevent blanking of the boundary portion. You can Similarly, the blank areas can be prevented by overlapping the print areas at the boundary between the character and the graphic and the boundary between the graphic and the graphic. Therefore, by analyzing the PDL data, it is possible to accurately know the boundaries of images of different colors.

In addition, in the electrophotographic color image forming apparatus, the transfer quality may be deteriorated near the black characters and lines on the high-dark color background to deteriorate the print quality. The quality of the image can be improved by extracting such a region and replacing the monochrome black with the process black (black expressed by the color material of YMCK). Also in this case, the region to be replaced with the process black can be accurately determined by analyzing the PDL data and accurately detecting the black character or line with the dark background.

Although the embodiments of the invention have been described above, the technical scope of the invention according to the present application is not limited to the above embodiments. The invention described in the claims can be implemented by adding various changes to the above embodiment. It is obvious from the description of the claims that such an invention belongs to the technical scope of the invention according to the present application.

[0043]

As is apparent from the above description, the image processing apparatus of the present invention analyzes PDL data to identify the type of image. Therefore, it is possible to avoid erroneously identifying an image as in the case of analyzing a raster image. Further, flexibility and expandability of image processing can be enhanced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of an image processing apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a flow of image data according to the first embodiment.

FIG. 3 is an explanatory diagram showing an example of PDL data.

FIG. 4 is an explanatory diagram illustrating an image processing method according to the first embodiment.

FIG. 5 is a block diagram showing a configuration of a second embodiment of the image processing apparatus of the present invention.

FIG. 6 is an explanatory diagram showing a flow of image data according to the second embodiment.

FIG. 7 is an explanatory diagram showing an example of a raster image obtained by expanding PDL data.

FIG. 8 is a block diagram showing a configuration of an image processing unit 146 according to the second embodiment.

FIG. 9 is a block diagram showing a configuration of an image processing apparatus according to a third embodiment of the present invention.

FIG. 10 is an explanatory diagram showing an example of data stored in a page memory 142.

FIG. 11 is an explanatory diagram illustrating an image processing method according to the third embodiment.

FIG. 12 is a block diagram showing a configuration of an image processing unit 146 according to the third embodiment.

FIG. 13 is a block diagram illustrating a configuration of a conventional image processing apparatus.

FIG. 14 is an explanatory diagram showing a method for increasing the resolution in the main scanning direction.

FIG. 15 is an explanatory diagram showing a flow of image data in a conventional image processing apparatus.

[Explanation of reference numerals] 102 host computer 104 interface cable 106 external interface 108 PDL buffer 110 page memory 112 rasterizer 114 ROM 116 bus 118 RAM 120 image interface 122 image compression unit 124 image enhancement unit 126 image forming apparatus 128 image decoding unit 132 buffer memory 134 code memory 136 image analysis unit 137 enhancement unit 139 raster expansion unit 140 rasterizer 142 page memory 146 image processing unit 200 spatial filter 202 tone correction unit 204 halftone generation unit 206 image decoding unit 208 image enhancement unit

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location // H04N 1/40 H04N 1/40 F

Claims (4)

[Claims] 1. A storage unit for storing PDL data described in a page description language, a generation unit for generating an image based on the PDL data stored in the storage unit, and the storage unit stored in the storage unit. An image processing apparatus comprising: an identification unit that identifies the type of the image based on PDL data; and a processing unit that processes the image based on the type of the image. 2. The identifying means includes means for identifying an edge area from the image based on the PDL data, and the processing means smoothes the edge area and enhances the contrast of the edge area. The image processing apparatus according to claim 1, further comprising: 3. The generating means and the identifying means each have a semiconductor device for processing the PDL data, and each of the semiconductor devices has the P in the storage means.
The image processing apparatus according to claim 1, wherein DL data is accessed in parallel. 4. The image processing apparatus according to claim 1, wherein the identifying means identifies an image area and an area other than the image area.