JP4526577B2 - Image processing apparatus, image processing system, and image processing method - Google Patents

Description

  The present invention relates to an image processing apparatus, an image processing system, and an image processing method used for a printer, a digital copying machine, a facsimile, a multifunction image processing apparatus, an MFP (multifunction printer), and the like.

Conventionally, for example, Patent Document 1 discloses an image processing apparatus that fuses an image signal and a separation signal by setting a signal value representing an achromatic color to a pixel that is a black character region. In the image processing apparatus disclosed in Patent Document 1, when an image signal and a separation signal are merged, correction is performed on black character pixels so that R = G = B, and the extraction unit R = G = The pixel B is re-extracted as a black character. Further, this Patent Document 1 discloses a method of merging by setting the values of a and b signals to 0 in the Lab color system. In addition, a method of merging black character information by using special values (R = 255, G = B = 0, etc.) that are not generally used in ordinary color images is shown. Furthermore, in order to remove pixels erroneously detected at the time of re-extraction, a comprehensive determination is made using the extraction results of peripheral pixels.
JP-A-8-98016

  Thus, conventionally (for example, in Patent Document 1), a black character pixel is subjected to achromatization processing such as R = G = B or a = b = 0 in Lab, and these are separated by the separation result extraction unit. Black character information is detected (re-extracted) based on this information. However, there is a problem that the black character information cannot be detected (re-extracted) with high accuracy by the separation result extraction means only by the achromatization process.

  An object of the present invention is to provide an image processing apparatus, an image processing system, and an image processing method that enable black character information to be detected (re-extracted) with higher accuracy than in the past.

In order to achieve the above-mentioned object, the invention according to claim 1 includes: a first separation unit that determines whether a target pixel is a black character pixel with respect to an input color image signal;
When the first separation means determines that the target pixel is not a black character pixel, no processing is performed on the target pixel, and when it is determined that the target pixel is a black character pixel, the target in the color image signal Achromatic means for performing achromatic processing to remove the color component of the pixel;
A third separation unit for detecting a black character pixel by determining whether or not the target pixel is an achromatic color from the image signal from the achromatization unit, and a black character pixel detected by the first separation unit; A difference determination unit that detects a pixel area that has a separation result different from that of the first separation unit in the third separation unit, based on a difference from the black character pixel detected by the third separation unit;
When U representing the saturation in the YUV signal, which is the luminance color signal, is 0 or positive with respect to the pixel area detected by the difference determination means, U is added with a predetermined value k and output, and U is negative K is subtracted and output. When V representing the saturation in the YUV signal, which is a luminance color signal, is 0 or positive, a predetermined value k is added to V and output. When V is negative, k is output. Chromatic means for subtracting and outputting;
Compression means for performing irreversible compression processing on the image signal processed by the chromaticization means;
Storage means for storing the image signal compressed by the compression means;
A second means for detecting a black character pixel by determining whether or not the target pixel is an achromatic color with respect to the image signal expanded by the expansion means and the image signal expanded by the expansion means; And separating means.

According to a second aspect of the present invention, in the image processing apparatus according to the first aspect, the second separation unit and the third separation unit detect black character pixels by detecting an achromatic pixel block on a white ground. It is characterized by performing detection .

According to a third aspect of the present invention, there is provided first separation means for determining whether or not a target pixel is a black character pixel with respect to an input color image signal;
When the first separation unit determines that the target pixel is not a black character pixel, no processing is performed on the target pixel, and when it is determined that the target pixel is a black character pixel, the target in the color image signal Achromatic means for performing achromatic processing to remove the color component of the pixel;
A third separation unit for detecting a black character pixel by determining whether or not the target pixel is an achromatic color from the image signal from the achromatization unit, and a black character pixel detected by the first separation unit; A difference determination unit that detects a pixel area that has a separation result different from the first separation unit in the third separation unit based on a difference from the black character pixel detected by the third separation unit;
When U representing the saturation in the YUV signal, which is a luminance color signal, is 0 or positive with respect to the pixel area detected by the difference determination means, U is added with a predetermined value k and output, and U is negative K is subtracted and output. When V representing the saturation in the YUV signal, which is a luminance color signal, is 0 or positive, a predetermined value k is added to V and output. When V is negative, k is output. Chromatic means for subtracting and outputting;
Compression means for performing irreversible compression processing on the image signal processed by the chromaticization means;
Storage means for storing the image signal compressed by the compression means;
A second means for detecting a black character pixel by determining whether or not the target pixel is an achromatic color with respect to the image signal decompressed by the decompression means and the decompression means; And separating means.

According to a fourth aspect of the present invention, in the image processing system according to the third aspect , the second separation means and the third separation means detect black character pixels by detecting an achromatic pixel block on a white ground. It is characterized by performing detection .

The invention according to claim 5 includes a first separation step of determining whether or not the target pixel is a black character pixel with respect to the input color image signal;
If it is determined in the first separation step that the target pixel is not a black character pixel, the target pixel is not processed, and if it is determined that the target pixel is a black character pixel, the target in the color image signal An achromatization process for performing an achromatization process to reduce or remove the color component of the pixel;
A third separation step of detecting a black character pixel by determining whether the target pixel is an achromatic color from the image signal from the achromatization step, and a black character pixel detected by the first separation step; A difference determination step of detecting a pixel region that has resulted in a separation result different from the first separation step in the third separation step based on a difference from the black character pixel detected by the third separation step;
When U representing the saturation in the YUV signal, which is a luminance color signal, is 0 or positive with respect to the pixel area detected by the difference determination step, U is added with a predetermined value k and output, and U is negative K is subtracted and output. When V representing the saturation in the YUV signal, which is a luminance color signal, is 0 or positive, a predetermined value k is added to V and output. When V is negative, k is output. A subtractive chromaticization process,
A compression step of performing irreversible compression processing on the image signal processed by the chromaticization step;
An accumulation step of accumulating the image signal compressed in the compression step;
A second step of detecting a black character pixel by determining whether or not the target pixel is an achromatic color with respect to the image signal expanded by the expansion step and the image signal expanded by the expansion step; And a separation step.

According to a sixth aspect of the present invention, in the image processing method according to the fifth aspect , the second separation step and the third separation step detect black character pixels by detecting an achromatic pixel block on a white ground. It is characterized by performing detection .

According to the first to sixth aspects of the present invention, the first separation means for determining whether the target pixel is a black character pixel with respect to the input color image signal;
When the first separation means determines that the target pixel is not a black character pixel, no processing is performed on the target pixel, and when it is determined that the target pixel is a black character pixel, the target in the color image signal Achromatic means for performing achromatic processing to remove the color component of the pixel;
A third separation unit for detecting a black character pixel by determining whether or not the target pixel is an achromatic color from the image signal from the achromatization unit, and a black character pixel detected by the first separation unit; A difference determination unit that detects a pixel area that has a separation result different from that of the first separation unit in the third separation unit, based on a difference from the black character pixel detected by the third separation unit;
When U representing the saturation in the YUV signal, which is the luminance color signal, is 0 or positive with respect to the pixel area detected by the difference determination means, U is added with a predetermined value k and output, and U is negative K is subtracted and output. When V representing the saturation in the YUV signal, which is a luminance color signal, is 0 or positive, a predetermined value k is added to V and output. When V is negative, k is output. Chromatic means for subtracting and outputting;
Compression means for performing irreversible compression processing on the image signal processed by the chromaticization means;
Storage means for storing the image signal compressed by the compression means;
A second means for detecting a black character pixel by determining whether or not the target pixel is an achromatic color with respect to the image signal expanded by the expansion means and the image signal expanded by the expansion means; Therefore, the black character information can be detected (re-extracted) with higher accuracy than in the prior art.

Specifically, an area that is highly likely to be erroneously detected by the second separation means due to image degradation caused by compression / expansion means or the like can be chromatic, and the margin for erroneous detection can be increased. The part to be converted can be kept to the minimum necessary.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration example of an image processing apparatus according to a first embodiment of the present invention. Referring to FIG. 1, the image processing apparatus according to the first embodiment includes an image input unit 101, a scanner γ correction unit 102, a first image area separation unit (first separation unit) 103, and an edge amount. Calculation means 104, filter processing means 105, color component control means 106, color correction means 107, second image area separation means (second separation means) 108, under color removal / black generation means 109, A printer γ correction unit 110, a halftone processing unit 111, and an image output unit 112.

  In the image processing apparatus according to the first embodiment, the following processing is performed. That is, the original optically read by the image input means 101 such as a scanner is converted into an 8-bit digital image signal of rgb and output. The output image signal is input to the scanner γ correction unit 102, and the reflectance linear rgb signal is converted into a density linear RGB signal by an LUT (look-up table) or the like. At this time, the gray balance is achieved, and when the R, G, and B pixel values are equal, the gray level is adjusted.

  The image signal rgb from the image input means 101 is simultaneously input to the first image area separation means 103, and the image input to the first image area separation means 103 is converted into a black character image area by the first image area separation means 103. And a color character image area and other picture areas. The picture area refers to a halftone image area (characters on halftone dots are identified as a picture area), a continuous tone image area, and a background area.

  Here, the first image region separation means 103 performs image region separation processing by an image region separation method as disclosed in, for example, Japanese Patent No. 3153221 and Japanese Patent Laid-Open No. 5-48892. That is, in the above image area separation method, the determination is comprehensive based on edge area detection, halftone dot area detection, white background area detection, and chromatic / achromatic area detection, and characters on the white ground are determined to be character areas. A halftone dot image or a continuous tone image including characters on a halftone dot is determined as a picture area (an area other than a character). Further, for the character area, a black character area and a color character area are further discriminated by detecting the chromatic / achromatic area. In FIG. 1, the separation signal s1 input to the filter processing means 105 is a signal indicating a character area (character image area). The signal c1 input to the color component control means 106 is a signal indicating a black character area (black character image area).

  Further, the edge amount calculating means 104 calculates an edge amount e1 indicating the degree of edge of the input image using the g signal.

  The filter processing unit 105 adaptively performs edge enhancement processing on the RGB image signal from the scanner γ correction unit 102 based on the determination result s1 from the first image area separation unit 103 and the edge amount e1 from the edge amount calculation unit 104. Alternatively, a smoothing process is performed. Specifically, a uniform edge emphasis filter is applied to the character region (both black character and color character regions) of the RGB image signal, and a smoothing filter is applied to the pattern region, and then adaptation based on the edge amount is applied. Perform edge enhancement processing. By such a filtering process, the sharpness can be satisfied at the character portion, and the moire can be suppressed at the halftone dot portion and the sharpness at the character on the halftone dot can be satisfied at the pattern portion.

  The color component control unit 106 controls the color component of the image signal from the filter processing unit 105 based on the black character separation result (black character region signal) c1 from the first image area separation unit 103. It has become.

  FIG. 2 is a diagram illustrating a configuration example of the color component control unit 106. In the example of FIG. 2, the color component control unit 106 receives the average value units 1061 to 1063 for obtaining the average value of the input RGB signals, and the average value signal from the average value units 1061 to 1063 and the original RGB signal. and a selector 1064 that switches based on c1. More specifically, the selector 1064 selects the output from the average means 1061 to 1063 for the pixels determined to be black characters based on the signal c1, and selects the pixels determined to be not black characters. Is configured to select and output a signal value from the filter processing means 105. In the example shown in FIG. 2, in the case of a black character pixel, R ′ = G ′ = B ′ = ave (R, G, B), and by setting all the pixels to the same value, It is a signal indicating that there is. That is, the color component control means 106 embeds the black character code in the image as R ′ = G ′ = B ′ = ave (R, G, B).

  The image signal R′G′B ′ from the color component control unit 106 is input to the color correction unit 107, and the color correction unit 106 converts the RGB signal into a CMY system suitable for a printer color material by masking calculation or the like. It is designed to convert the signal. Various methods are conceivable as the color correction processing. Here, it is assumed that a masking operation such as the following equation (Equation 1) is performed.

Number 1
C = α11 × R + α12 × G + α13 × B + β1
M = α21 × R + α22 × G + α23 × B + β2
Y = α31 × R + α32 × G + α33 × B + β3

  In the above equation 1, α11 to α33 and β1 to β3 are predetermined color correction coefficients, and the output CMY is also an 8-bit (0 to 255) signal.

  Further, the image data from the color component control means 106 is also input to the second image area separating means 108, and the second image area separating means 108 detects (re-extracts) black character pixels. .

  FIG. 3 is a diagram illustrating a configuration example of the second image area separating unit 108. In the example of FIG. 3, the second image area separation unit 108 includes a black candidate pixel detection unit 1081, a connectivity determination unit 1082, a white pixel detection unit 1083, a 3 × 3 expansion processing unit 1084, and a logical product. Circuits 1085 and 1087 and 5 × 5 expansion processing means 1086 are provided.

  The black character pixel detection processing (re-extraction processing) in the second image area separation means 108 is performed as follows. That is, for the R′G′B ′ signal, the black candidate pixel detection unit 1081 determines whether or not the target pixel is R = G = B and G> th1, and the target pixel is R = G = B and If G> th1, 1 is output as the black candidate pixel. Here, th1 is a density threshold value that determines the black level. In this way, the black candidate pixel detection unit 1081 detects black pixels having a predetermined density or higher. The detection result of the black candidate pixel detection unit 1081 is input to the connectivity determination unit 1082, and the connectivity determination unit 1082 performs pattern matching based on, for example, a pattern as shown in FIG. Due to the nature of the character image, pixels (black character pixels) constituting a black character do not exist by being isolated by 1 dot or 2 dots. That is, the character is characterized in that continuous black pixels are arranged in continuous white pixels. For example, the separation means disclosed in Japanese Patent No. 3153221 also incorporates pattern matching utilizing its properties, and if such detection is performed in the previous stage, there will be no black pixels isolated in the black character portion. It can be said. Therefore, in the example of FIG. 4, pattern matching is performed using a connectivity determination pattern of 3 × 3 pixels, and pixels in which three black candidate pixels are connected in either the vertical or horizontal diagonal direction across the target pixel. By detecting, other isolated pixels can be removed. In the connectivity determination, since the pixel of interest is the center of 3 × 3 pixels, one black pixel is missing at the end point of the line or the corner of the broken line / curve, but the final pixel is obtained by the 5 × 5 expansion processing for the black ground edge at the subsequent stage. Since it is detected as a black character, there is no problem. By performing the connectivity determination as described above, R = G = B pixels scattered in the pattern are not erroneously determined as black characters.

  In the configuration example of FIG. 3, the detection accuracy is further increased by the white pixel detection means 1083. That is, as described above, since the black character region indicates a black character on the white background, the feature is that there are white pixels around the black character pixel. The white pixel detection means 1083 determines whether or not the pixel has R = G = B and G <th2, and if R = G = B and G <th2, outputs 1 as a white pixel. Further, the white pixels detected in this manner are expanded by 3 × 3 by the expansion processing means 1084, and a logical product with the signal output from the connectivity determination means 1082 is obtained in the logical product circuit 1085. The white pixel is an area that is expanded by one pixel from the original white pixel by 3 × 3 expansion, and a black pixel area adjacent to the white background can be detected by taking a logical product with the black character candidate pixel. Black blocks resembling black characters scattered in the design can be removed here because there are no white pixels around them.

  As described above, a signal obtained by removing R = G = B pixels other than black characters is expanded by the 5 × 5 expansion processing means 1086 (expanded into a black character region having a width of 5 dots), and further in the AND circuit 1087. By taking a logical product with the signal output from the connectivity determination means 1082, the black character area (for two dots) that protrudes from the white background side is eliminated. The black character separation signal c2 detected as described above is a region having a width of 3 dots in the outline of the black character on the white background, and is output for use in subsequent processing.

  In addition, as a filtering process performed before the second image area separation unit 108, sufficient emphasis processing is performed on the characters on the white background, and white spots generated around the characters are left as they are. The black character pixels can be detected (re-extracted) with high accuracy by using a mechanism that prevents white spots that occur during emphasis for ground black characters.

  The image signal from the color correction unit 107 is converted into a CMYK signal by the under color removal / black generation unit 109. The under color removal / black generation means 109 generates a K signal that is a black component and performs under color removal (UCR) from the CMY signal. Here, the under color removal / black generation unit 109 performs different under color removal / black generation for the black character pixel and other pixels based on the black character separation result c2 from the second image area separation unit 108. It has become.

  The generation of the K signal and the removal of the undercolor from the CMY signal for pixels that are not black character pixels (non-black character pixels) are performed as follows.

Number 2
K = Min (C, M, Y) × β4
C ′ = C−K × β5
M ′ = M−K × β5
Y ′ = Y−K × β5

  Here, Min (C, M, Y) is the smallest of the CMY signals, and β4 and β5 are 8-bit signals with predetermined coefficients. Further, the generation of the K signal for the black character pixel and the removal of the under color from the CMY signal are performed as follows.

Number 3
K = Min (C, M, Y)
C '= 0
M '= 0
Y '= 0

  As described above, since black character pixels are reproduced with a single color of K toner, good black character quality can be obtained without causing coloring or resolution reduction due to color misregistration during plate misregistration.

  The signal processed by the under color removal / black generation unit 109 is subjected to γ correction in accordance with the printer engine characteristics by the printer γ correction unit 110 and further subjected to halftone processing by the halftone processing unit 111 to output an image. Output in means 112.

  In the configuration example of FIG. 1, the halftone processing unit 111 is configured to switch the halftone processing method using the separation result c <b> 2 by the second image area separation unit 108. That is, more specifically, the halftone processing unit 111 performs, for example, an error diffusion process advantageous for reproduction of character sharpness on a pixel determined to be a black character, and is determined to be a non-black character such as a pattern portion. Dither processing, which is advantageous for graininess and gradation reproducibility, is applied to the pixels. In this example, such switching is performed, but there is no problem if the entire surface is processed by error diffusion processing.

  As described above, in the first embodiment, based on the separation result of the first separation unit 103, the black character pixel (black character region pixel) is set to R = G = B, and the color component is reduced. 2 separation means 108 detects (re-extracts) black character pixels based on the R = G = B information, and performs processing such as under color removal and black ink generation on the basis of the detected (re-extracted) black character pixel information. By doing so, high-quality image reproduction can be realized.

  In the above processing example, the color component of the black character pixel is completely set to 0. However, the present invention is not limited to this. For example, the color component suppression unit 106 can suppress the color component so that the value of ΔRGB is equal to or less than a predetermined value. In this case, the second image area separation unit 108 performs black candidate pixel detection. In addition, it is only necessary to determine that a pixel having ΔRGB equal to or smaller than a predetermined threshold is a black candidate pixel. In this way, even when the image after the color component suppression processing is displayed on a monitor such as a PC without being completely achromatic, the uncomfortable feeling of the black character image can be relatively reduced.

  As described above, the present invention is based on the first separation unit that determines the attribute of the target pixel with respect to the input color image signal, and the target pixel based on the attribute of the target pixel determined by the first separation unit. Color component control means for performing predetermined processing on the color components, and second separation means for determining the attribute of the target pixel with respect to the image signal processed by the color component control means. The color component control means performs a predetermined process on the color component of the target pixel so as to improve the attribute determination accuracy of the target pixel in the second separation means.

  Specifically, as a first example of the present invention, the first separation unit has a black character pixel determination function for determining whether or not the target pixel is a black character pixel as an attribute of the target pixel. If the first separation means determines that the target pixel is not a black character pixel, the means performs a chromaticization process for increasing the color component of the target pixel. The second separation means It has a function of detecting (extracting) a black character pixel by analyzing at least a color component of the image signal processed by the control means.

  That is, in this first example, the color component control means 106 increases the color components of non-black character pixels. By doing so, it is possible to reduce the detection (extraction) of black characters by mistake in the pattern portion, and to perform highly accurate black character detection (extraction).

  FIG. 5 is a block diagram of the color component control means 106 of the first example. Referring to FIG. 5, in block 1065, the color component control means 106 converts the input RGB signal into a YUV signal of a luminance color signal. Here, the RGB → YUV conversion formula is as follows.

Number 4
Y = (R + 2G + B) / 4
U = (R−G) / 2
V = (B−G) / 2

  In the YUV signal, the Y signal is a signal representing luminance, and the U and V signals are signals representing saturation. That is, Equation 4 is a conversion formula in which the values of U and V are both 0 when an achromatic color, that is, R = G = B. In blocks 1066 to 1068 for converting the saturation component, the color component is changed with respect to the YUV signal converted in block 1065.

  Here, the block 1068 is achromatic means for outputting the U component as 0. Similarly, the block 1069 is achromatic means for outputting the V component as 0. On the other hand, the block 1066 adds and outputs a predetermined value k to U when U is 0 or positive, and outputs it by subtracting k when U is negative. It is a chromatic means. Note that k is preferably a small value at a level where the color change cannot be visually recognized, and an appropriate value that is sufficiently determined as a chromatic pixel by the second image area separation in the subsequent stage. . Similarly, the block 1067 is chromaticization means for chromaticizing V. The Y signal from the block 1065 is output to the selector 1064 without performing any processing.

  The selector 1064 performs switching based on the black character separation signal c 1 from the first image area separation means 103. That is, if the black character separation signal c1 from the first image area separation means 103 indicates a black character pixel, the selector 1064 selects the output from the achromatic means 1068 and 1069 and indicates a non-black character pixel. If so, the output from the chromaticizing means 1066, 1067 is selected. Next, the signal Y and the output signals U ′ and V ′ from the selector 1064 are converted into an R′G′B ′ signal whose color component is controlled in a block 1070 for performing inverse conversion from YUV to RGB and output. Here, the conversion equation of YUV → RGB is as follows.

Number 5
G = Y− (2U + 2V) / 4
R = 2U + G
B = 2V + G

  With the configuration as shown in FIG. 5, even if there is an achromatic color or a signal very close to an achromatic color in the non-black character part, the chromaticization means chromaticizes the necessary and sufficient amount, The black character re-extraction accuracy (detection accuracy) at the subsequent stage can be improved without giving the impression that the color has changed.

  Further, as a second example of the present invention, the first separation unit has a color character pixel determination function for determining whether the target pixel is a color character pixel as an attribute of the target pixel, and a color component control unit When the first separation means determines that the target pixel is a color character pixel, the chromaticization process is performed to increase the color component of the target pixel, and the second separation means It has the function of detecting (extracting) color character pixels by analyzing at least the color components of the image signal processed by the component control means.

  FIG. 6 is a block diagram of the color component control means 106 of the second example. Referring to FIG. 6, this color component control means 106 also has chromaticization blocks 1066 and 1067 similar to those in FIG. 5, and is configured to increase the saturation. In another path, the input U and V signals are input to the selector 1064 as they are. The selector 1064 switches between them based on the color character separation signal c3 determined by the first separation means 103. That is, the selector 1064 selects a signal from the chromatic blocks 1066 and 1067 for the color character pixel, and selects a through signal for the non-color character pixel.

  By increasing the saturation of the color character in this way, it is less likely that the color character is mistakenly identified as a black character in the second separation in the subsequent stage, and the black character pixel detection (re-extraction) accuracy can be improved.

  Further, as a third example of the present invention, the first separation unit has a character pixel determination function for determining whether the target pixel is a character pixel as an attribute of the target pixel, and the color component control unit includes: When it is determined by the first separation means that the target pixel is not a character pixel, chromaticization processing for increasing the color component of the target pixel is performed, and the second separation means is controlled by the color component control means. It has a function of detecting (extracting) black character pixels by analyzing at least a color component of the processed image signal.

  FIG. 7 is a block diagram of the color component control means 106 of the third example. FIG. 7 differs from FIG. 6 in the separation signal input to the selector 1064, and the other configuration is the same as in FIG. That is, in FIG. 7, the character separation result s1 is input to the selector 1064. Referring to FIG. 7, the color component control means 106 of the third example selects signals from the chromaticization blocks 1066 and 1067 for non-character pixels, thereby increasing the saturation of the non-character pixels. On the other hand, a pixel determined as a character (that is, a pixel of a black character and a color character) is set to through without controlling the saturation component. By doing so, it is less likely that the achromatic pixel in the pattern area is erroneously extracted as a black character by mistake.

  As described above, in the present invention, as in the first, second, and third examples, the color component control unit 106 is configured to improve the attribute determination accuracy of the target pixel in the second separation unit 108. By performing predetermined processing on the color components of the pixels, it is possible to detect (re-extract) black character information with higher accuracy than in the past.

  Note that the processes described above can be combined. For example, when the first separation unit 103 determines that the target pixel is a black character pixel, the color component control unit 106 performs the achromatic processing for reducing or removing the color component of the target pixel in the first example. (I.e., if the first separation unit 103 determines that the target pixel is a black character pixel, a decolorization process is performed to reduce or remove the color component of the target pixel. If it is determined by one separation means that the target pixel is not a black character pixel, a chromaticization process for increasing the color component of the target pixel can also be performed). Alternatively, it is possible to perform achromatization processing on black character pixels, pass through on color character pixels, and perform chromaticization processing on non-character regions.

  In the configuration example of FIG. 1, it is possible to determine the black character by providing the second separation unit 108 with a separation circuit having the same configuration as the first separation unit 103, but the first separation unit 103 Since the circuit configuration is very large, there is a problem that the hardware cost increases. In contrast to this, information is embedded in the image data according to the result of the first separation means 103 as in the present invention, and data processing (chromatic and / or chromatic and / or so that the separation circuit in the subsequent stage can be simplified. By performing (achromatization), it is possible to use a separated signal with low hardware cost and high accuracy in subsequent processing.

(Second Embodiment)
FIG. 8 is a diagram showing a configuration example of an image processing apparatus according to the second embodiment of the present invention. Referring to FIG. 8, in the image processing apparatus of the second embodiment, the output from the color component control means 106 is temporarily accumulated in the accumulation means 113 and accumulated in the accumulation means 113 in the image processing apparatus in FIG. The signal is read and the processing after the color correction means 107 and the second image area separation means 108 is performed. That is, in the second embodiment (in the image processing apparatus of FIG. 8), each processing means 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112 other than the storage means 113 is used. Is the same as that of the first embodiment (image processing apparatus of FIG. 1).

  As described above, the second embodiment of the present invention includes the accumulation unit 113 that accumulates the image signal processed by the color component control unit 106 in the image processing apparatus according to the first embodiment. The means 108 is characterized in that the signal stored in the storage means 113 is read and processed.

  In a copy job or the like over a plurality of sheets, a configuration in which image data is temporarily stored is general. However, in the present invention, a configuration in which black character separation information is embedded in image data is used, so that it is not necessary to separately store a separation signal ( In the configuration of FIG. 8, there is no need to provide storage means for storing separated signals separately from the storage means 113), and the memory capacity can be saved.

(Third embodiment)
FIG. 9 is a diagram illustrating a configuration example of an image processing apparatus according to the third embodiment of the present invention. Referring to FIG. 9, in the image processing apparatus of the third embodiment, the output from the color component control means 106 is compressed by the compression means 115 in the image processing apparatus of FIG. The signal stored in the means 113 is read out and decompressed by the decompression means 116, and the processing after the color correction means 107 and the second image area separation means 108 is performed. That is, in the third embodiment (in the image processing apparatus of FIG. 9), each processing means 101, 102, 103, 104, 105, 106, 107, 108 other than the compression means 115, the storage means 113, and the decompression means 116. , 109, 110, 111, 112 are the same as those of the first embodiment (image processing apparatus of FIG. 1).

  As described above, according to the third embodiment of the present invention, in the image processing apparatus according to the first embodiment, the compression unit 115 that compresses the image signal processed by the color component control unit 106, and the compression unit 115 Storage means 113 for storing the image signal compressed in step (1), and expansion means (116) for expanding the image signal stored in the storage means (113). The second separation means (108) is decompressed by the expansion means (116). It is characterized in that processing is performed on the received image signal.

  Here, the compression unit 115 may perform a lossless compression process, or may perform a lossy compression process. However, it is preferable to use the irreversible compression processing method in consideration of the number of sheets stored in the storage unit 113 and the data transfer rate. However, in this case, in the lossy compression, the black character information embedded by the color component control unit 106 and the chromaticization processing for improving the re-extraction accuracy are distorted due to deterioration due to compression and expansion. The amount of signal level change varies depending on the compression processing method, applied filter characteristics, document type, and the like, but sufficient detection (re-extraction) of black character information is performed by the second image area separation unit 108. Color component control according to the compression processing method of the compression means 115 is necessary so that it can be performed.

  Further, it is desirable that the compression means 115 compresses the image signal after converting it to a luminance / color difference system signal. As described above, since the process of embedding the black character separation information is performed by achromatizing the black character, it is desirable that the change in the saturation component in the black character portion due to compression and expansion is as small as possible. If the image signal is converted into a luminance color difference signal such as YUV, the saturation component in the black character portion becomes 0, and it is difficult for deterioration due to compression and expansion. In the configuration in which the RGB signal is compressed for each plate, when any of the R, G, and B signals changes due to compression deterioration, the achromatic pixel becomes chromatic. In the case of YUV, even if a change occurs with respect to Y, it remains achromatic if there is no change in U and V. For the reasons described above, it is desirable that the compression unit 115 compresses the image signal after converting it to a luminance / chrominance signal.

  In the first, second, and third embodiments described above, the chromaticization process in the color component control unit 106 increases the color component only when the color component of the processing target pixel is smaller than a predetermined value. Can do.

  In FIG. 5, control is performed so that non-black character pixels are uniformly chromaticized. Although saturation control is such that it cannot be recognized visually, it is desirable not to change saturation. Corresponding to this, in order to minimize the portion that controls the color component, the chromaticization processing in the color component control means 106 increases the color component only when the color component of the processing target pixel is smaller than a predetermined value. You can make it.

  FIG. 10 shows a configuration example of the color component control means 106 that increases the color component only when the color component of the processing target pixel is smaller than a predetermined value. That is, in the example of FIG. 10, the color component control means 106 is configured to increase the color component only when the saturation component is smaller than a predetermined value among the input non-black character pixels. For example, in the block 1066 of FIG. 10, when the absolute value of the U component is 2 or less, the saturation component is controlled to increase by k, but when the absolute value of the U component is larger than 2, the processing is not performed. It has become. The same applies to block 1067. That is, in the example of FIG. 10, a pixel having sufficient saturation is not detected (re-extracted) as a black character by mistake, so it may be through, and a pixel that is near achromatic and may be erroneously determined as a black character. Only to chromaticize. In this way, the chromaticization process can be minimized and color reproducibility can be guaranteed.

  For the same purpose as described with reference to FIG. 10, in the first, second, and third embodiments described above, the color component control unit detects (extracts) black character pixels by the second separation unit 108. In this case, increase the color component of the image area that is more likely to be erroneously detected (extracted) as a black character pixel, or detect it as a black character pixel. It is possible to increase the color components only for image regions that are highly likely to be extracted. As a result, it is possible to minimize the control of the color components other than the black character pixels by the color component control means 106.

  That is, the second image area separation means 108 shown in FIG. 3 detects black character information (re-extraction) by detecting an R = G = B pixel block adjacent to a white pixel. In such a simple detection method, when there is a gray image on the white ground, it may be erroneously determined as a black character. For example, a monochrome photograph pasted on a white paper corresponds to this case. Even in the case of a monochrome image, pixels with R = G = B are rarely present in a lump, and the separation means in FIG. 3 determines only the three-dot width adjacent to the white background as a black character area. Although there is substantially no problem, it is preferable that there is no such misjudgment in order to reproduce a higher quality image.

  For this reason, in the present invention, an image region that is likely to be erroneously determined is detected in advance by the subsequent image region separation unit 108, and correction is performed so that erroneous determination does not occur only in this image region, thereby minimizing the color component control. I try to keep it in the limit area.

  FIG. 11 shows other image regions that are likely to erroneously detect (extract) pixels that are not black character pixels as black character pixels when the second separating unit 108 detects (extracts) black character pixels. An example of the configuration of the color component control means 106 that increases the color component more than the area of the image area or increases the color component only for an image area that is likely to be erroneously detected (extracted) as a black character pixel is shown. ing. That is, in the example of FIG. 11, the color component control means 106 detects a portion B that is likely to cause erroneous separation in the subsequent image area separation in addition to the portion A of the achromatization means for black character pixels. Have.

  In the configuration example of FIG. 11, a signal in which the black character pixel is achromatic by the selector 1064 is input to the third image area separation unit 1073. The third image area separating unit 1073 has the same configuration as the above-described second image area separating unit 108 (FIG. 3), and is configured to detect an achromatic pixel block on the white ground. A difference between the black character separation result c4 detected by the third image area separation unit 1073 and the original black character separation result c1 is detected by the difference determination unit 1074, and the difference determination unit 1074 sets an erroneously determined image region as c5. To detect. Then, chromaticization is performed by the chromaticizers 1071 and 1072 on the erroneously determined image region c5 and output in block 1070.

  Here, in the third image area separation unit 1073, the black character detection (re-extraction) parameter may be set as a parameter such that the black character is more easily detected. By doing in this way, it is possible to detect in advance a location where false detections increase due to image degradation caused by compression / expansion means or the like.

  As described above, the color component control unit 106 shown in FIG. 11 can colorize regions that are likely to be erroneously detected by the second image area separation unit 108 in the subsequent stage, and can increase the margin for erroneous detection. In addition, the chromatic part can be kept to the minimum necessary.

  In the configuration example of FIG. 11, an example in which the detection unit having the same configuration as the second image area separation unit 108 is used for the third separation unit 1073 has been shown. When it is known that there is a high possibility that a pixel close to achromatic color is erroneously detected, a white background / background region detection result from the first image region separation unit 103 and a black character can be obtained without providing the third separation unit 1073. A region to be chromaticized in advance can be specified based on the detection result and pixel information that is substantially achromatic.

(Fourth embodiment)
In the fourth embodiment of the present invention, in the image processing apparatuses of the first, second, and third embodiments described above, an image signal that has been subjected to predetermined processing by the color component control unit 106 is transmitted by the system or a user. The color component control means has a processing function of converting to a specified predetermined image format (compression method, compression rate, image resolution, color space) and transferring it to an external device, and according to the specified predetermined image format It is characterized by controlling.

  Here, the control of the color component control means according to a predetermined image format includes control for expanding the area of the black character pixel determined by the first separation means 103 as an area to be achromatic. Yes.

  FIG. 12 is a diagram illustrating a configuration example of an image processing apparatus according to the fourth embodiment of the present invention. In the example of FIG. 12, in the image processing apparatus of FIG. 9, the image signal stored in the storage unit 113 is converted into a predetermined format and transferred to an external device. That is, in the example of FIG. 12, when the image signal stored in the storage unit 113 is converted into a predetermined format and transferred to an external device, the signal from the storage unit 113 is read and decompressed by the compression / expansion unit 117. Then, the resolution conversion means 119 converts it to a predetermined resolution. In order to reduce the data size at the time of external transfer, for example, a 600 dpi resolution image is converted to 300 dpi or 200 dpi. Further, it can be converted into a standard signal such as sRGB conversion in the block 120, converted into the JPEG format by the JPEG compression / decompression unit 121, and transferred to the external device via the NIC 122.

  In some cases, the externally transferred image signal is used as image data scanned as an application on a PC, and is input to the image forming apparatus again and copied. For example, a case where an unnecessary portion such as a punched hole image in an image read by editing software is removed or an image edited by pressing a stamp is output is an example. In such a case, the JPEG compression / decompression unit 121 again performs JPEG decompression via the NIC 122, and further converts into a device-dependent RGB signal at the block 120, and the resolution conversion unit 119 converts the original resolution (600 dpi). And compressed by the compression / expansion means 117 and stored in the storage means 113. When the storage in the storage unit 113 ends, the system controller (not shown) performs post-processing after the decompression unit 116.

  In FIG. 12, the black character separation information embedded in the image data by the first color component control means 106 is deteriorated / changed by the resolution conversion means 119 and the JPEG compression / expansion means 121, and therefore again. The accuracy of detection (re-extraction) of black character information in the second image area separation means 108 at the time of copy output is deteriorated.

  The fourth embodiment of the present invention is intended to satisfy the image quality of black characters even at the time of re-output through format conversion at the time of external transfer, and the first color component control means 106 is transferred to the external transfer. Control is performed in accordance with the image format at the time. Specifically, further color component control is performed on black character pixels and non-black character pixels so that the detection margin at the time of redetection (reextraction) is improved.

  For example, with respect to chromaticization for non-black character pixels, there is a method of outputting with stronger chromaticization than the chromaticization performed by the first color component control means 106.

As another method, there is a method of expanding an achromatic region. For example, JPEG compression is a method of converting a luminance color difference signal (YC _b C _r ) for each 8 × 8 block size and compressing an image using DCT conversion. When JPEG compression is performed on an achromatic black character pixel, if another pixel in the 8 × 8 block is a chromatic pixel, the black character pixel is chromatic. Normally, there is a white background area around the pixels that are determined to be black characters, and there are no highly saturated color pixels, but there are pixels that have a slight saturation even on a white background. A problem occurs. This is also noticeable when the compression rate is set high.

On the other hand, if all the pixels in the 8 × 8 block are achromatic pixels, the C _b C _r component becomes 0 when the YC _b C _r signal is used, and the achromatic information can be stored without deterioration. Therefore, when it is known that the first color component control means 106 performs JPEG compression and outputs the result to the outside, the first color component control means 106 determines whether the non-black character pixel in the block is chromatic / non-empty depending on the presence or absence of the black character pixel in the block to be compressed. It is configured to control the chromatic processing, and when there are black character pixels, all other chromatic pixels may be corrected to achromatic pixels.

  In addition, as described above, there are no highly saturated color pixels around the black character pixels, so it is not problematic in terms of image quality to achromatic all the pixels in the block, but for example, the block size is larger. In the compression method, there is a case where image quality deterioration is caused by achromatic pixels. In such a case, if the chromatic pixels having sufficient saturation in the block are not subjected to achromatic processing, only the pixels having relatively low saturation are achromatic. Good.

  Further, although the method for achromatizing the pixels around the black character in the block unit has been described, it may be configured to achromatize not the block unit but the region in which the black character pixel is expanded by several pixels. In this case, the number of pixels to be expanded may be determined according to the data format to be converted. The same applies to the resolution. If the area to be achromatized is wide when converted to low resolution data, the black character information can be stored well.

  As described above, by controlling the first color component control means 106, it is possible to embed black character information accurately in a signal converted into a different data format such as resolution conversion and compression method. High image quality can be achieved. In the above description, re-copying with this image processing apparatus has been described as an example. However, it is also effective for an external image processing apparatus or image processing program that can re-extract embedded attribute information and realize adaptive processing. is there.

(Fifth embodiment)
In the fifth embodiment of the present invention, in the image processing apparatuses of the second and third embodiments, the image signal stored in the storage means 113 is converted into a predetermined image format designated by the system or the user. Processing means for transferring to an external device, and the processing means includes second color component control means for performing chromaticization and / or achromatization processing on the image signal stored in the storage means 113 again. The image signal stored in the storage unit 113 is subjected to chromaticization and / or achromatization processing again and transferred to an external device.

  Here, the second color component control unit re-chromatizes and re-colors the image signal stored in the storage unit 113 according to the attribute information identified from the image signal stored in the storage unit 113. It is possible to transfer to an external device after applying achromatization processing.

  Alternatively, the second color component control unit re-chromatizes and / or achromatics the image signal stored in the storage unit 113 according to the attribute of the target pixel determined by the first separation unit 103. It is also possible to transfer to an external device after performing the conversion process.

  FIG. 13 is a diagram illustrating a configuration example of an image processing apparatus according to the fifth embodiment of the present invention. In the example of FIG. 13, a second color component control unit 118 is further provided between the compression / decompression unit 117 and the resolution conversion unit 119 in the configuration of FIG.

  The configuration example of FIG. 13 is effective when the image data processed and accumulated in the accumulation unit 113 for copy output is also used as an output to an external device. That is, as described above, the embedding of black character information optimized for copy output is deteriorated by resolution conversion or JPEG compression as it is. However, if a wide range of achromatization is performed as in the fourth embodiment in consideration of external transfer, image quality may be degraded for copy output. Therefore, in the fifth embodiment of the present invention, the second color component control unit 118 executes correction processing of black character information in accordance with the data format transferred externally.

  Specifically, the second color component control unit 118 again has the presence of the image signal stored in the storage unit 113 according to the attribute information identified from the image signal stored in the storage unit 113. Saturation and / or desaturation processing can be performed and transferred to an external device.

  Alternatively, the second color component control unit 118 re-chromatizes and / or disables the image signal stored in the storage unit 103 according to the attribute of the target pixel determined by the first separation unit 103. It can also be subjected to a coloring process and transferred to an external device.

  Further, the control by the second color component control means 118 may be performed based on the black character separation result c1 from the first image area separation means 103, or from the image data by the re-extraction means (not shown). The embedded black character information may be re-extracted and performed based on the re-extraction result.

  Incidentally, in each of the above-described embodiments, the storage unit 113 can store specified output conditions and processing contents as information together with the compressed image data. Saving specified output conditions and processing details as information is effective when the accumulated image data is output again at a later date by specifying output from the operation panel or the like. Reads information on the stored image data, and displays the image quality mode (character photo mode, character mode, photo mode, etc.), document type mode (printing paper, print document), applied filter parameters, parameters for suppressing color components, etc. By recognizing, it is possible to optimize the processing contents in the post-compression color correction means and halftone processing means.

  Furthermore, when transferring an image signal to an external device, it is desirable that the processing content applied to the image signal can be output as header information or footer information. Specifically, the converted resolution information, information indicating that the signal is an sRGB signal, JPEG quality, processing content in the second color component control means, and the like may be added to the information and output. it can. By doing so (that is, when the image signal is transferred to the external device, the processing content applied to the image signal is saved in the header information and transferred to the external device), and then input again from the outside. In this case, it can be converted into an appropriate image format according to the header information.

  Further, the second image area separation means 108 can perform highly accurate black character detection (extraction) by changing the separation method and parameters based on the header information. For example, the threshold values for chromatic pixel determination and achromatic pixel determination can be controlled according to the compression rate and resolution. As a specific example, when the compression rate is high, there is a high possibility that deterioration has occurred. Therefore, the determination threshold value is relaxed to make it easier to detect black characters. However, if the compression ratio is higher, false detection will increase greatly when trying to re-extract black characters, and the picture quality will deteriorate significantly. Set to OFF. As described above, the optimum image quality can be obtained by optimally controlling the second image area separating unit in accordance with the compression rate.

  Also, regarding the resolution, once converted to a low resolution image of a certain degree or less, it may be preferable to turn off the black character re-extraction function, and thus it can be controlled in this way.

  Further, when the process of changing the color component is performed by external editing, the black character re-extraction function can be turned off.

  Furthermore, the black character re-extraction function can be turned off when information about embedding of black character information is not added to the image signal input from the external device or when there is no header information.

  In other words, in the image processing apparatus in which attribute determination is performed by the second separation unit 108 on the image data input from the external device, the black character extraction method of the second separation unit 108 is controlled according to the header information. be able to.

  Further, image data input from an external device is stored in the storage unit 113, the image signal stored in the storage unit 113 is read, and the attribute of the target pixel is detected (extracted) by the second separation unit 108 to perform image processing. In the image processing apparatus to be applied, when the header information indicating the processing content is not attached to the input image signal, the black character extraction by the second separation unit 108 can be restricted or not performed.

  In this way, by controlling the use and non-use of the second image area separation means 108 and the parameters according to the information added to the image data, it is possible to output the optimum image quality that can be reproduced. It becomes possible.

  As described above, according to the present invention, based on the first separation unit for determining the attribute of the target pixel with respect to the input color image signal, and the attribute of the target pixel determined by the first separation unit, A color component control unit that performs predetermined processing on the color component of the target pixel; and a second separation unit that determines an attribute of the target pixel with respect to the image signal processed by the color component control unit. The means performs predetermined processing on the color component of the target pixel so as to improve the attribute determination accuracy of the target pixel in the second separation means (more specifically, the first separation means Having a black character pixel determination function for determining whether or not the target pixel is a black character pixel, and the color component control unit determines that the target pixel is not a black character pixel by the first separation unit. Increase pixel color component The second separating means has a function of detecting (extracting) black character pixels by analyzing at least the color components of the image signal processed by the color component control means. ), Black character information can be detected (re-extracted) with higher accuracy than in the past.

  More specifically, the black character information embedded as R = G = B may be deteriorated due to compression, expansion, etc., and detection (re-extraction) of black character information may not be performed successfully. In order to provide an image processing apparatus that is highly resistant to deterioration of pixel information corresponding to the case, in addition to achromatic black characters, non-black character pixels are chromatic. In addition, the chromaticization process is performed only on necessary pixels, such as a part that is likely to be erroneously separated when detecting (extracting) black character information in the subsequent stage, or a chromatic process is not performed on sufficient chromatic pixels. I have to.

  In addition, when copying a plurality of sheets or performing electronic sorting, there is a configuration in which image data embedded with black character information is temporarily stored for a plurality of pages in a large-capacity storage unit such as a hard disk device and is read out. In such a case, it is possible to save the capacity of the storage means (storage means) and to reduce the amount of data transferred to the bus by adopting the configuration of the present invention that does not hold the separation information as data.

  Furthermore, when storing and accumulating in the storage means (accumulation means), it is common to use a method of compressing and accumulating image data. In such a case, the previously embedded black character information is not degraded as much as possible. It is necessary to accumulate at. According to the present invention, preprocessing is performed so that the black character information is not deteriorated even when data changes due to lossy compression.

  In addition, when the image signal stored in the storage unit is transferred to the outside, it is usually further compressed and output by a compression unit such as JPEG, but processing with a different compression method or a different compression rate is performed. As a result, the black character information embedded in the image data may be damaged. In such a case, high-quality reproduction cannot be performed when the data once transferred to the outside is input and output again, or when transferred to another MFP having the same image processing system and output. On the other hand, in the present invention, in order to be able to save black character information even when the accumulated signal is compressed and output by another compression means, the second color component control means is provided and the black character code is stored. Is corrected to a more robust state.

  In the present invention, when image data is stored, the image processing content applied to the image data, such as the image quality mode, the scaling factor, and the compression rate, is stored in the header information together with the image data, thereby re-extracting black characters. This makes it possible to perform optimal processing.

  In each of the above-described examples, the first image area separating unit and the second image area separating unit determine a black character area for a black character on a white background, and a black character area for a black character on a halftone dot. Although the explanation has been made on the assumption that it is not, this is not the case.

  Even when the first image area separating means determines a black character on a halftone dot or color ground as a black character area, the black code is embedded by correcting the black character area pixel to R = G = B, If R = G = B is extracted by the image area separating means and black character processing is performed, the same effect can be obtained. Further, processing such as chromaticizing non-black character pixels is effective in improving the separation accuracy in the second separation means, and the same effect can be obtained.

  In each of the above-described examples, the image output unit 112 is described as a printer. However, the image output unit 112 may have any function as long as it has an image output function. Applies.

  FIG. 14 is a diagram illustrating a hardware configuration example of the image processing apparatus according to the present invention. Referring to FIG. 14, this image processing apparatus is realized by, for example, a personal computer and the like, and includes a CPU 21 that controls the whole, a ROM 22 that stores a control program of the CPU 21, and a RAM 23 that is used as a work area of the CPU 21. A hard disk 24, an image input unit 101 such as a scanner, an image output unit (for example, a display or a printer) 112, and a communication unit (for example, a NIC) 122.

  Here, the hard disk 24 corresponds to the storage means 113. The CPU 21 has the functions of the above-described means 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 115, 116, 117, 118, 119, 120, 121 and the like. .

  Note that the function of each means 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 115, 116, 117, 118, 119, 120, 121, etc. in the CPU 21 is, for example, software. It can be provided in the form of a package (specifically, an information recording medium such as a CD-ROM).

  In the present invention, the processing in each means 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 115, 116, 117, 118, 119, 120, 121, etc. is performed by a computer (CPU 21). Can be provided in the form of a program to be realized.

  In other words, the image processing apparatus of the present invention causes a general-purpose computer system having a scanner, a printer, and the like to read a program recorded on a recording medium such as a CD-ROM, and processes the program on the microprocessor of the general-purpose computer system. It is also possible to implement in an apparatus configuration that executes In this case, a program for executing the processing of the present invention (that is, a program used in the hardware system) is provided in a state recorded on a medium. The recording medium on which the program is recorded is not limited to the CD-ROM, and a ROM, RAM, flexible disk, memory card, or the like may be used. The program recorded on the medium is installed in a storage device incorporated in the hardware system, for example, the hard disk 24 and is activated to execute the program, thereby realizing the processing of the present invention.

In the above description, the present invention has been described as an image processing apparatus. However, for those skilled in the art, the present invention can also be understood as an image processing system and, further, as an image processing method.

It is a figure which shows the structural example of the image processing apparatus of the 1st Embodiment of this invention. It is a figure which shows the structural example of a color component control means. It is a figure which shows the structural example of a 2nd image area separation means. It is a figure which shows the example of a connectivity determination pattern. It is a figure which shows the other structural example of a color component control means. It is a figure which shows the other structural example of a color component control means. It is a figure which shows the other structural example of a color component control means. It is a figure which shows the structural example of the image processing apparatus of the 2nd Embodiment of this invention. It is a figure which shows the structural example of the image processing apparatus of the 3rd Embodiment of this invention. It is a figure which shows the other structural example of a color component control means. It is a figure which shows the other structural example of a color component control means. It is a figure which shows the structural example of the image processing apparatus of the 4th Embodiment of this invention. It is a figure which shows the structural example of the image processing apparatus of the 5th Embodiment of this invention. It is a figure which shows the hardware structural example of the image processing apparatus of this invention.

Explanation of symbols

21 CPU
22 ROM
23 RAM
24 hard disk 101 image input means 112 image output means 122 communication means 102 scanner γ correction means 103 first image area separation means (first separation means)
104 Edge amount calculation means 105 Filter processing means 106 Color component control means 107 Color correction means 108 Second image area separation means (second separation means)
109 Under color removal / black generation means 110 Printer gamma correction means 111 Halftone processing means 113 Storage means 115 Compression means 116 Expansion means 117 Compression / expansion means 118 Second color component control means 119 Resolution conversion means 120 Block 121 JPEG compression / Stretching means

Claims (6)

First separation means for determining whether or not the target pixel is a black character pixel with respect to the input color image signal;
When the first separation means determines that the target pixel is not a black character pixel, no processing is performed on the target pixel, and when it is determined that the target pixel is a black character pixel, the target in the color image signal Achromatic means for performing achromatic processing to remove the color component of the pixel;
A third separation unit for detecting a black character pixel by determining whether or not the target pixel is an achromatic color from the image signal from the achromatization unit, and a black character pixel detected by the first separation unit; A difference determination unit that detects a pixel area that has a separation result different from that of the first separation unit in the third separation unit, based on a difference from the black character pixel detected by the third separation unit;
When U representing the saturation in the YUV signal, which is the luminance color signal, is 0 or positive with respect to the pixel area detected by the difference determination means, U is added with a predetermined value k and output, and U is negative K is subtracted and output. When V representing the saturation in the YUV signal, which is a luminance color signal, is 0 or positive, a predetermined value k is added to V and output. When V is negative, k is output. Chromatic means for subtracting and outputting;
Compression means for performing irreversible compression processing on the image signal processed by the chromaticization means;
Storage means for storing the image signal compressed by the compression means;
A second means for detecting a black character pixel by determining whether or not the target pixel is an achromatic color with respect to the image signal expanded by the expansion means and the image signal expanded by the expansion means; And an image processing apparatus. 2. The image processing apparatus according to claim 1, wherein the second separation unit and the third separation unit detect a black character pixel by detecting an achromatic pixel block on a white ground. Processing equipment. First separation means for determining whether or not the target pixel is a black character pixel with respect to the input color image signal;
When the first separation means determines that the target pixel is not a black character pixel, no processing is performed on the target pixel, and when it is determined that the target pixel is a black character pixel, the target in the color image signal Achromatic means for performing achromatic processing to remove the color component of the pixel;
A third separation unit for detecting a black character pixel by determining whether or not the target pixel is an achromatic color from the image signal from the achromatization unit, and a black character pixel detected by the first separation unit; A difference determination unit that detects a pixel area that has a separation result different from that of the first separation unit in the third separation unit, based on a difference from the black character pixel detected by the third separation unit;
Predetermined to U when U representing the saturation in the YUV signal, which is a luminance color signal, is 0 or positive with respect to the pixel area detected by the difference determination means with respect to the pixel area detected by the difference determination means K is subtracted and output when U is negative, and when V representing saturation in the YUV signal, which is a luminance color signal, is 0 or positive, V is set to a predetermined value k. Chromaticizing means for adding and outputting, and subtracting and outputting k when V is negative;
Compression means for performing irreversible compression processing on the image signal processed by the chromaticization means;
Storage means for storing the image signal compressed by the compression means;
A second means for detecting a black character pixel by determining whether or not the target pixel is an achromatic color with respect to the image signal decompressed by the decompression means and the decompression means; And an image processing system. 4. The image processing system according to claim 3, wherein the second separation unit and the third separation unit detect black character pixels by detecting an achromatic pixel block on a white ground. Processing system. A first separation step of determining whether the target pixel is a black character pixel with respect to the input color image signal;
If it is determined in the first separation step that the target pixel is not a black character pixel, the target pixel is not processed, and if it is determined that the target pixel is a black character pixel, the target in the color image signal An achromatization process for performing an achromatization process to reduce or remove the color component of the pixel;
A third separation step of detecting a black character pixel by determining whether the target pixel is an achromatic color from the image signal from the achromatization step, and a black character pixel detected by the first separation step; A difference determination step of detecting a pixel region that has resulted in a separation result different from the first separation step in the third separation step based on a difference from the black character pixel detected by the third separation step;
When U representing the saturation in the YUV signal, which is a luminance color signal, is 0 or positive with respect to the pixel area detected by the difference determination step, U is added with a predetermined value k and output, and U is negative K is subtracted and output. When V representing the saturation in the YUV signal, which is a luminance color signal, is 0 or positive, a predetermined value k is added to V and output. When V is negative, k is output. A subtractive chromaticization process,
A compression step of performing irreversible compression processing on the image signal processed by the chromaticization step;
An accumulation step of accumulating the image signal compressed in the compression step;
A second step of detecting a black character pixel by determining whether or not the target pixel is an achromatic color with respect to the image signal expanded by the expansion step and the image signal expanded by the expansion step; An image processing method comprising: a separation step. 6. The image processing method according to claim 5, wherein the second separation step and the third separation step detect black character pixels by detecting an achromatic pixel block on a white ground. Processing method.

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