JP3944032B2 - Image processing apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and a method thereof, and for example, relates to image processing for dividing an image into regions.
[0002]
[Prior art]
When copying a document in which characters and halftone images are mixed, the copying machine performs various processes on the image data output from the scanner, and then prints it out. For example, when sharpening characters, a sharpness filter is applied. However, moire occurs when the same filter processing is applied to the halftone image. Accordingly, a plurality of copy modes, such as a mode in which character reproduction is emphasized and a mode in which dot image reproduction is emphasized, are prepared in a copying machine and the like, and filter processing corresponding to the copy mode is performed.
[0003]
Some color copying machines separate character and line drawing areas and halftone image areas (image area separation), and switch the filtering process applied to each area.
[0004]
The color copier further determines whether the character and line drawing area or the separated image is achromatic, and if it is achromatic, prints using only the black color material, Some improve the reproducibility of black thin lines. In order to suppress erroneous determination due to noise when determining whether or not the color is achromatic, there is a preprocessing for performing a smoothing process on the target pixel data.
[0005]
[Problems to be solved by the invention]
Due to the phase difference of the RGB signals generated when the image is read by the scanner, a color component is generated at the edge portion of the achromatic character and the line drawing area (hereinafter referred to as “reading color shift”). When the reading color misregistration occurs, the area is not determined to be an achromatic color although it is originally an achromatic character and line drawing area. The RGB signal phase difference, which is the cause of reading color misregistration, is caused by mechanical vibration when scanning the scanner head, chromatic aberration of an optical system such as a lens, and the like. If it is attempted to suppress vibration and chromatic aberration, the cost of the device will increase considerably.
[0006]
The smoothing process described above is an effective method for suppressing the color misregistration that occurs at the edges of black characters and black thin lines on a white background (hereinafter referred to as “white background”). If smoothing processing is performed on black thin lines or black characters (called “color ground”), a color is generated at the edge of the black thin lines or black characters, making it impossible to determine an achromatic region.
[0007]
The present invention is for solving the above-described problems individually or collectively, and an object thereof is to suppress the influence of reading color misregistration when performing image area separation.
[0008]
[Means for Solving the Problems]
The present invention has the following configuration as one means for achieving the above object.
[0009]
An image processing apparatus according to the present invention refers to an area around a target pixel of an input image signal, an averaging unit that averages the color components of the target pixel, and a pixel based on the averaged image signal A determination unit that determines whether the pixel is an achromatic color or a chromatic color, and when a plurality of consecutive pixels including the target pixel have a predetermined arrangement of determination results of the determination unit and a change in brightness, And correction means for correcting the determination result of the achromatic color by the determination means to the determination result of the chromatic color.
[0010]
The image processing method according to the present invention refers to an area around the target pixel of the input image signal, averages the color components of the target pixel, and determines whether the pixel is achromatic based on the averaged image signal. If a plurality of continuous pixels including the target pixel have a predetermined arrangement of determination results and a change in brightness, the determination result of the achromatic color by the determination with respect to the target pixel is present . The correction is made to the determination result of coloring.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an image processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.
[0012]
[Constitution]
FIG. 1 is a block diagram illustrating a configuration example of a color copying machine as an image processing apparatus according to an embodiment.
[0013]
The image input unit 1 outputs digital image signals R1, G1, and B1 color-separated into RGB three colors for each pixel of the color image. The image input unit 1 corresponds to an image reader of a color copying machine, which includes an optical system such as a lamp, a mirror and a lens, an RGB 3-line CCD, an A / D converter, and the like. The 3-line CCD is arranged so that the distance between them is 6 lines. The image input unit 1 adjusts the position of the RGB image signal in the sub-scanning direction, for example, by delaying the R and G image signals in accordance with the B image signal. The image input unit 1 is not limited to an image reader, and may be an interface for inputting an image from a computer device or the like.
[0014]
The image signals R1, G1, and B1 output from the image input unit 1 are subjected to color correction processing using a matrix operation of 3 × 3 pixels in the input masking unit 2, and a standard color space such as NTSC-RGB or The signals are converted into sRGB image signals R2, G2, and B2 and input to the spatial filter 3, a character / line image detection unit 8 and a color determination unit 9 described later.
[0015]
The character / line image detection unit 8 determines whether or not the input image region is a character / line image region from the image signals R2, G2, and B2, and outputs an MJDET signal indicating the determination result to the spatial filter unit 3 and the saturation suppression unit 4. To do. The color determination unit 9 determines whether the input image is an achromatic color from the image signals R2, G2, B2, and outputs a BWDET signal indicating the determination result to the saturation suppression unit 4.
[0016]
The spatial filter 3 performs spatial filter processing on the image signals R2, G2, and B2, and the characteristics of the spatial filter are switched by the MJDET signal output from the character / line image detection unit 8. The spatial filter 3 includes a buffer for synchronizing the image signal with the detection / determination timing of the character / line image detection unit 8 and the color determination unit 9. Similarly, the character / line image detection unit 8 has a buffer for synchronizing the determination result to the determination timing of the color determination unit 9, but it will be easily understood by those skilled in the art. Is omitted.
[0017]
The image signals R3, G3, and B3 output from the spatial filter 3 are input to the saturation suppression unit 4, and processing for suppressing the saturation is performed based on the MJDET signal and the BWDET signal.
[0018]
Image signals R4, G4, and B4 output from the saturation suppression unit 4 are input to the output masking unit 5, subjected to logarithmic conversion (luminance density conversion), and then subjected to masking and UCR processing to obtain C1, M1, Converted to Y1 and K1 density signals.
[0019]
The image signals C1, M1, Y1, and K1 output from the output masking unit 5 are input to the gamma conversion unit 6 and subjected to gradation conversion based on the gradation characteristics of the printer unit 7.
[0020]
Image signals C2, M2, Y2, and K2 output from the gamma conversion unit 6 are input to the printer unit 7 to form a print image.
[0021]
[Character line drawing detection unit]
The character / line image detection unit 8 determines the image signal in units of pixels, determines whether or not it is a pixel constituting a character or a line image, and if it is determined as a pixel constituting a character or a line image as an MJDET signal, '1' If it is determined that the pixel is not a pixel constituting a character or line drawing, “0” is output.
[0022]
FIG. 2 is a block diagram illustrating a configuration example of the character / line image detection unit 8.
[0023]
The brightness signal generation unit 11 converts the image signal into a brightness signal L by the following equation.
L = (R + 2 x G + B) / 4… (1)
[0024]
The signal L output from the lightness signal generation unit 11 is input to the edge amount determination unit 12 and the binarization unit 13. The edge amount determination unit 12 calculates the Laplacian (edge amount) of the signal L and outputs “1” when the absolute value of the Laplacian is equal to or greater than a predetermined value as the output signal ED, and “0” when the absolute value is less than the predetermined value. Output.
[0025]
The binarization unit 13 binarizes the target pixel using an average value of pixel values in a predetermined area (for example, a 5 × 5 pixel area) around the target pixel as a threshold value. FIG. 3 shows an example of the binarization result of the line drawing area, and FIG. 4 shows an example of the binarization result of the halftone dot area (the output BD of the binarization unit 13).
[0026]
The isolation amount determination unit 14 that receives the output signal BD of the binarization unit 13 refers to a predetermined area (for example, a 9 × 9 pixel area) around the target pixel and outputs an output signal SUM corresponding to the isolation state of the target pixel. Output. That is, in the predetermined area around the target pixel, the BD = '0' pixel adjacent to the BD = '1' pixel is counted, and if the count value (isolation amount) is less than the predetermined value, SUM = '1 If 'exceeds a predetermined value, SUM =' 0 'is output.
[0027]
In the example of the line drawing area shown in FIG. 3, since the pixels of BD = “1” are continuous, the isolated amount is equal to or less than a predetermined value, and SUM = “1” is output. On the other hand, in the example of the halftone dot area shown in FIG. 4, since the pixel of BD = “1” exists in isolation, the isolation amount exceeds a predetermined value and SUM = “0” is output. Note that the pixel of BD = “1” tends to be continuous not only in the line drawing area but also in the character area, and the output signal SUM of the isolated amount determination unit 14 for the character area becomes “1”. In this way, the isolation amount determination unit 14 outputs the signal SUM that separates the character line drawing area and the halftone dot area.
[0028]
The determination unit 15 that receives the output signal ED of the edge amount determination unit 12 and the output signal SUM of the isolation amount determination unit 14 has ED = '1' (large edge amount) and SUM = '1' (small isolation amount) In this case, MJDET = '1' indicating that the pixel of interest is in the character / line drawing area is output.
[0029]
In the case of a continuous halftone area such as a silver halide photograph, the output signal SUM of the isolated amount determination unit 14 may be '1' or '0' depending on the image. Separation from is not sufficient. However, since the edge amount of the continuous halftone area is small, ED = '0' (edge amount is small) is output from the edge amount determination unit 12, and the determination unit 15 determines that the continuous halftone area is a character line drawing area. Can be prevented.
[0030]
[Color judgment part]
FIG. 5 is a block diagram illustrating a configuration example of the color determination unit 9.
[0031]
The color space conversion unit 31 converts the color space of the image signal, and converts the color space of the input image signal into a lightness signal component representing brightness and a chromaticity component representing color. Specifically, the image signals R2, G2, and B2 are simply converted into the lightness signal L and the chromaticity signals Ca and Cb by the equation (2).
L = (R2 + 2 x G2 + B2) / 4
Ca = (R2-G2) / 2… (2)
Cb = (R2 + G2-2 x B2) / 4
[0032]
The lightness signal L and the chromaticity signals Ca and Cb output from the color space conversion unit 31 are input to the line memories 32, 33, and 34, respectively, as a signal delayed by one line and a signal delayed by two lines. The data is input to the area processing unit 34. The signal name shown in FIG. 5 represents the delay amount (relative position in the sub-scanning direction) by its subscript. For example, L (-1) is the signal one line before L (0), L (−2) represents the signal two lines before.
[0033]
The area processing unit 34 performs an averaging process on each of the lightness signal L and the chromaticity signals Ca and Cb with reference to the 3 × 3 pixel area around the target pixel. That is, the area processing unit 34 refers to nine pixels in the 3 × 3 pixel region, and outputs the average value aveL of the brightness signal and the average values aveCa and aveCb of the chromaticity signals Ca and Cb.
[0034]
The signals aveCa and aveCb output from the area processing unit 34 are input to the saturation calculation unit 35, and the saturation S of the target pixel is calculated by Expression (3).
S = √ (aveCa ² + aveCb ² )… (3)
[0035]
For the sake of simplicity, the saturation S may be compared with the absolute values | aveCa | and | aveCb |, and the larger absolute value may be used as the saturation S. FIG. 6 is a diagram showing the relationship between the saturation S0 calculated by the equation (3) and the saturation S1 calculated simply.
[0036]
The saturation S output from the saturation calculation unit 35 is input to the determination unit 36 and compared with a predetermined threshold value. The determination unit 36 determines that the target pixel is an achromatic color when the saturation S is equal to or less than a predetermined threshold and outputs a signal MONO = '1', and if the saturation S exceeds the predetermined threshold, the target pixel is determined to be a chromatic color. Signal MONO = '0'.
[0037]
The line memory 37 gives a delay of up to four lines to the signal MONO, and inputs a signal obtained by delaying the signal MONO by 1, 2, 3 and 4 lines to the correction unit 39. Further, the line memory 38 gives a delay of up to 4 lines to the signal aveL, and inputs a signal obtained by delaying the signal aveL by 1, 2, 3 and 4 lines to the correction unit 39.
[0038]
[Scanning color shift]
Before describing the operation of the correction unit 39, the reading color misregistration will be described in detail.
[0039]
FIG. 7 is a schematic diagram showing the relationship between the original image and the RGB signal photoelectrically converted by the image input unit 1, showing the read value and saturation S of the RGB signal corresponding to each sampling position 0 to 5 of the original image, In the example, the phase of the R signal is shifted by one sampling with respect to the phase of the G and B signals.
[0040]
Due to the phase difference of the RGB signals, saturation S that does not exist in the original image is generated at sampling positions 1 and 4 corresponding to the black edge portion of the original image, and an image with a color on the black edge portion is generated. As shown in FIG. 7, the saturation S generated by the RGB read signal is suppressed by the averaging process of the area processing unit 34, but the determination unit 36 may still determine the black edge portion as a chromatic color. This depends on the setting of the determination threshold of the determination unit 36, but when the saturation of the background of the original is almost zero, if the phase difference of the RGB signal is small, the black edge portion is obtained by the averaging processing of the area processing unit 34. Saturation S generated in the above is effectively suppressed, and the determination unit 36 does not erroneously determine the black edge portion as a chromatic color. However, when the phase difference of the RGB signal is 0.5 pixels or more, the determination unit 36 is more likely to determine the black edge portion as a chromatic color.
[0041]
8 and 9 are schematic diagrams showing the output of the determination unit 36. FIG. The pixel indicated by X (-1) in FIG. 8 corresponds to the sampling position 0 in FIG. 7, the pixel indicated by X (0) corresponds to the sampling position 1, and the pixel indicated by X (1) corresponds to the sampling position 2. Similarly, the pixel indicated by X (-1) in FIG. 9 corresponds to the sampling position 3 in FIG. 7, the pixel indicated by X (0) corresponds to the sampling position 4, and the pixel indicated by X (1) corresponds to the sampling position 5. . In FIG. 8 (a) and FIG. 9 (a), the pixel of X (0) is determined to be a chromatic color based on the phase difference of the RGB signals described above.
[0042]
[Correction section]
FIG. 10 is a flowchart showing the correction process of the correction unit 39.
[0043]
The correction unit 39 refers to the signal MONO (-3) for three consecutive pixels including the pixel of interest X (0) and its front and back, and the pixels X (-1), X (0), and X (1) It is determined whether or not the arrangement (arrangement) of the determination results of the determination unit 36 is “achromatic, chromatic, achromatic” (S1), and the arrangement of the determination results of the determination unit 36 is “achromatic, chromatic, no In the case of “coloration”, the brightness of the pixels X (−1), X (0), and X (1) is determined with reference to the signal aveL (−3) for three consecutive pixels (S2 and S3).
XL (-1)> XL (0)> XL (1)… (4)
XL (-1) <XL (0) <XL (1)… (5)
Where XL (-1) is the brightness of the pixel of X (-1) aveL (-3)
XL (0) is the pixel brightness of X (0) aveL (-3)
XL (1) is the pixel brightness of X (1) aveL (-3)
[0044]
If the condition of Expression (4) or Expression (5) is satisfied, the target pixel X (0) is determined as a pixel at the black edge, and the determination result of the target pixel X (0) is changed from chromatic to achromatic. Correction is performed and BWDET = '1' indicating an achromatic pixel is output (S4). On the other hand, if the arrangement of the determination results of the determination unit 36 does not indicate `` achromatic color, chromatic color, achromatic color '' or if the condition of Expression (4) or Expression (5) is not satisfied, the target pixel X (0 ) BWDET = MONO (-3) is output without correcting the determination result (S5). Then, the pixel of interest is advanced by one pixel (S6), and then the process returns to step S1.
[0045]
In this way, the chromatic color generated at the black edge due to the phase difference of the RGB signal by determining the arrangement (arrangement) of the determination result MONO between achromatic color and chromatic color and the magnitude relationship between the lightness aveL corresponding to them The determination result for the pixel can be corrected to “achromatic color” as shown in FIGS. 8B and 9B.
[0046]
In the above description, correction of determination when determining whether the line direction (main scanning direction) is an achromatic color or a chromatic color has been described. However, the correction unit 39 also applies to the direction orthogonal to the line (sub-scanning direction). In addition, the determination result of three pixels continuous in the sub-scanning direction is corrected. At that time, the correction unit 39 outputs signals MONO (-2), MONO (-3), and MONO (-4) output from the line memory 37, and signals aveL ( -2), aveL (-3), and aveL (-4) are referred to, and the determination result of the target pixel X (0) is corrected if necessary.
[0047]
Therefore, BWDET = MONO (-3) is output only when it is determined that correction of the determination result of the target pixel X (0) is unnecessary in both the main scanning direction and the sub-scanning direction. In this case, BWDET = '1' indicating the character / line drawing area is output as the determination result of the target pixel X (0).
[0048]
● Correction of chromatic color pixels In the above example, the judgment result for chromatic pixels generated at the black edge due to the phase difference of the RGB signal is corrected to “achromatic”. An example of correcting the color to “chromatic color” will be described.
[0049]
FIG. 11 is a diagram schematically showing a saturation signal of a document image having a color area on a white background (achromatic area).
[0050]
By the averaging process of the area processing unit 34, the saturation S at the sampling positions 2 and 4 decreases, and the saturation S at the sampling positions 1 and 5 increases. When the saturation of the color area is low, the pixels at the signing positions 1 and 5 where the saturation is increased by the averaging process are determined to be achromatic, but the pixels at the sampling positions 2 and 4 where the saturation is decreased are also achromatic. May be determined.
[0051]
12 and 13 are schematic diagrams showing the output of the determination unit 36 in such a case. As shown in FIG. 12 (a) and FIG. 13 (a), the pixel position corresponding to the sampling positions 2 and 4 is shown as X (0), and the pixel X (0) is caused by the decrease in saturation S due to averaging. It is determined as an achromatic color.
[0052]
FIG. 14 is a flowchart showing the correction processing of the correction unit 39.
[0053]
The correction unit 39 refers to the signal MONO (-3) for four consecutive pixels in the vicinity of the target pixel X (0), and the pixels X (-1), X (0), X (1), X (2 ) Is determined whether or not the arrangement (array) of the determination results of the determination unit 36 is “achromatic, achromatic, chromatic, achromatic” (S11), and the arrangement of the determination results of the determination unit 36 is “achromatic, In the case of `` achromatic, chromatic, achromatic '', refer to the signal aveL (-3) for four consecutive pixels, and pixel X (-1), X (0), X (1), X (2 ) Is determined (S12).
XL (-1)> XL (0)> XL (1) <XL (2)… (6)
[0054]
If the condition of Equation (6) is satisfied, the target pixel X (0) is determined as a pixel at the color edge portion, and the determination result of the target pixel X (0) is corrected from an achromatic color to a chromatic color. BWDET = '0' indicating the chromatic pixel is output (S13). On the other hand, when the arrangement of the determination results of the determination unit 36 does not indicate `` achromatic color, achromatic color, chromatic color, achromatic color '' or when the condition of Expression (6) is not satisfied, the pixel of interest X (0) BWDET = MONO (-3) is output without correcting the judgment result (S14). Then, the target pixel is advanced by one pixel (S15).
[0055]
Subsequently, the correction unit 39 refers to the signal MONO (-3) for four consecutive pixels in the vicinity of the target pixel X (0), and the pixels X (-2), X (-1), and X (0) , It is determined whether the alignment of the determination result of the determination unit 36 for X (1) is `` achromatic, chromatic, achromatic, achromatic '' (S16), and the alignment of the determination result of the determination unit 36 is `` achromatic color '' , Chromatic color, achromatic color, achromatic color '', refer to the signal aveL (-3) for four consecutive pixels, and pixel X (-2), X (-1), X (0), X The brightness of (1) is determined (S17).
XL (-2)> XL (-1) <XL (0) <XL (1)… (7)
[0056]
If the condition of Equation (7) is satisfied, the target pixel X (0) is determined as a pixel at the color edge portion, and the determination result of the target pixel X (0) is corrected from an achromatic color to a chromatic color. BWDET = '0' indicating a pixel is output (S18). On the other hand, when the arrangement of the determination results of the determination unit 36 does not indicate `` achromatic color, chromatic color, achromatic color, achromatic color '' or when the condition of Expression (7) is not satisfied, the pixel of interest X (0) BWDET = MONO (-3) is output without correcting the determination result (S19). Then, the pixel of interest is advanced by one pixel (S15), and the process returns to step S11.
[0057]
In this way, by determining the arrangement (arrangement) of the determination result MONO whether achromatic or chromatic and the magnitude relationship between the lightness aveL corresponding to them, the color edge of the low saturation region is determined by the phase difference of the RGB signal. As shown in FIGS. 12 (b) and 13 (b), it is possible to correct a misjudgment that occurs in the section as an achromatic pixel, and correct it to “chromatic color”. Of course, the sub-scanning direction may be determined and corrected in the same manner as the black region described above.
[0058]
Moreover, the example which correct | amends the chromatic color of a determination result to an achromatic color, and corrects an achromatic color to a chromatic color is not limited above. For example, if the RGB phase difference is large or the reference area of the averaging process is larger than 3 × 3 pixels, the determination result is displayed as `` achromatic color '' when it is determined that the chromatic color covers two pixels in the black edge area. FIG. 15 shows an example of correction to “.” FIG. 16 shows an example in which an erroneous determination of an achromatic color pixel occurring at a color edge in a low saturation region is corrected to “chromatic color” under the same conditions.
[0059]
[Spatial filter section]
Based on the output signal MJDET from the character / line image detection unit 8, the spatial filter unit 3 performs processing to give different spatial frequency characteristics to the character / line image region and other regions.
[0060]
FIG. 17 is a diagram showing the spatial frequency characteristics of the spatial filter. For pixels with MJDET = '1', edge enhancement characteristics are spatially filtered to improve the reproducibility of the character / line drawing area. For pixels with MJDET = '0', edge enhancement characteristics are applied. A spatial filter process is performed to weaken and suppress the occurrence of moire.
[0061]
[Saturation suppression section]
The saturation suppression unit 4 suppresses the saturation of the RGB image signal based on the output signal MJDET of the character / line drawing detection unit 8 and the output signal BWDET of the color determination unit 9.
[0062]
FIG. 18 is a block diagram illustrating a configuration example of the saturation suppression unit 4.
[0063]
The color space conversion unit 41 converts the color space of the image signal, and converts the color space of the input image signal into a lightness signal component representing brightness and a chromaticity component representing color. Specifically, the input image signals R3, G3, and B3 are simply converted into lightness signals L and chromaticity signals Ca and Cb by Expression (8).
L = (R3 + 2 x G3 + B3) / 4
Ca = (R3-G3) / 2… (8)
Cb = (R3 + G3-2 × B3) / 4
[0064]
The selector 42 is controlled by the logical product signal of the signal MJDET and the signal BWDET output from the AND gate 43. When the logical product signal is '1', the level 0 signal is displayed. When the logical product signal is '0', A chromaticity signal output from the color space conversion unit 41 is selected. That is, when the target pixel is in the character / line drawing area (MJDET = '1') and the achromatic color area (BWDET = '1'), the selector 42 outputs a chromaticity signal having a level of zero.
[0065]
The lightness signal output from the color space conversion unit 41 and the chromaticity signal output from the selector 42 are input to the color space inverse conversion unit 44 and converted into an image signal in the RGB color space by Equation (9). Ru
R4 = (4 × L + 5 × Ca + 2 × Cb) / 4
G4 = (4 × L-3 × Ca + 2 × Cb) / 4… (9)
B4 = (4 × L + Ca-6 × Cb) / 4
[0066]
Therefore, when the target pixel is in the character line drawing area and the achromatic color area, the selector 42 outputs Ca = Cb = 0, so that there is no color component, and the result of the inverse conversion according to the equation (8) is R4 = G4 = B4 = L, and RGB components are all equal gray scale image signals.
[0067]
Also, if the target pixel is in the non-character line drawing area or outside the achromatic area, the result of the inverse transformation by equation (8) is R4 = R3, G4 = G3, B4 = B3, and is input RGB image signal is output as it is.
[0068]
The image signal output from the saturation suppression unit 4 is input to the output masking unit 5 and converted into a CMYK image signal. At this time, the minimum value min (C, Y, M) of the CMY signal is set. A so-called 100% UCR is performed in which the difference between the CMY signal value and the K signal value is output as a CMY image signal as the K signal component. Therefore, when the RGB signal value input to the output masking unit 5 is R = G = B, the output CMY signal values are all zero, and the image is printed with only the K signal component.
[0069]
As described above, in the determination of dividing the pixel into the chromatic color and the achromatic color, due to the saturation component of the edge portion of the achromatic image area caused by one phase shift (reading color shift) of the input RGB signal, It is possible to avoid erroneous determination of determining a pixel as a “chromatic color”. As a result, it is possible to reproduce the edge portion of a black character or black line drawing with a single black color, and it is possible to improve the reproducibility of the black character or black line drawing, particularly a fine black character or black line drawing. In addition, even if the saturation process causes a decrease in saturation at the edge of a color character or color line drawing area, it is possible to avoid misjudgment to determine “achromatic color” and improve the quality of the printed image. I can plan.
[0070]
[Other Embodiments]
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer), and a device (for example, a copying machine and a facsimile device) including a single device. You may apply to.
[0071]
Another object of the present invention is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU or CPU) of the system or apparatus. Needless to say, this can also be achieved by the MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.
[0072]
Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.
[0073]
When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the flowcharts described above.
[0074]
【The invention's effect】
As described above, according to the present invention, it is possible to suppress the influence of the reading color shift when the image area is separated.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration example of a color copying machine;
FIG. 2 is a block diagram showing a configuration example of a character / line image detection unit;
FIG. 3 is a diagram showing an example of a binarization result (binary unit output BD) of a line drawing area;
FIG. 4 is a diagram illustrating an example of a binarization result (binary unit output BD) of a halftone dot region;
FIG. 5 is a block diagram illustrating a configuration example of a color determination unit;
FIG. 6 is a diagram showing a relationship between a chromaticity signal and saturation;
FIG. 7 is a schematic diagram showing a relationship between an original image and an RGB signal;
FIG. 8 is a schematic diagram showing an output of a determination unit;
FIG. 9 is a schematic diagram showing the output of the determination unit;
FIG. 10 is a flowchart showing correction processing of the correction unit;
FIG. 11 is a diagram schematically showing a saturation signal of a document image having a color area on a white background;
FIG. 12 is a schematic diagram showing the output of the determination unit;
FIG. 13 is a schematic diagram showing the output of the determination unit;
FIG. 14 is a flowchart showing correction processing of the correction unit;
FIG. 15 is a schematic diagram showing the output of the determination unit;
FIG. 16 is a schematic diagram showing the output of the determination unit;
FIG. 17 is a diagram showing the spatial frequency characteristics of the spatial filter;
FIG. 18 is a block diagram illustrating a configuration example of a saturation suppression unit.

Claims (7)

An averaging means for averaging the color components of the target pixel with reference to a region around the target pixel of the input image signal;
Determination means for determining whether a pixel is an achromatic color or a chromatic color based on the averaged image signal;
When a plurality of consecutive pixels including the target pixel have a predetermined arrangement of determination results of the determination unit and a change in brightness, the determination result of the achromatic color by the determination unit for the target pixel is determined as the determination result of the chromatic color. And an image processing apparatus. Wherein the correction means 4 consecutive pixels including the pixel of interest, is described in the case with a change in the arrangement and the intensity of the predetermined said determination result, to claim 1, characterized in that the correction Image processing device.   3. The image processing apparatus according to claim 1, further comprising a control unit that controls a saturation component of the image signal based on a determination result output from the correction unit. A discriminating means for discriminating whether or not the pixel is in the character line drawing area;
3. The control unit according to claim 1, further comprising: a control unit that controls a saturation component of a pixel determined to be in the character / line drawing area based on a determination result output from the correction unit. Image processing device. With reference to the area around the target pixel of the input image signal, the color components of the target pixel are averaged,
Based on the averaged image signal, determine whether the pixel is achromatic or chromatic,
When a plurality of consecutive pixels including the target pixel have a predetermined arrangement of determination results of the determination and a change in brightness, the determination result of the achromatic color by the determination for the target pixel is corrected to the determination result of chromatic color An image processing method. In the image processing device ,
A procedure for averaging the color components of the target pixel with reference to a region around the target pixel of the input image signal;
A procedure for determining whether a pixel is achromatic or chromatic based on the averaged image signal;
When a plurality of consecutive pixels including the target pixel have a predetermined arrangement of determination results and a change in brightness, the determination result of the achromatic color by the determination for the target pixel is corrected to a determination result of chromatic color And the steps to
A program for running In the image processing device,
A procedure for averaging the color components of the target pixel with reference to a region around the target pixel of the input image signal;
A procedure for determining whether a pixel is achromatic or chromatic based on the averaged image signal;
When a plurality of consecutive pixels including the target pixel have a predetermined arrangement of determination results and a change in brightness, the determination result of the achromatic color by the determination for the target pixel is corrected to a determination result of chromatic color And the steps to
The computer-readable recording medium which recorded the program for performing this .

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