JP2006311193A - Image processor, image reader provided with the same and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the generation of image quality degradation that an impression viewed in a color region close to an achromatic color becomes largely different from a source image due to the color vision characteristics of a human in color subtraction by the integration of colors when generating main images for respective colors for multilayering color images. <P>SOLUTION: When extracting from the source image the main images of characters or the like plotted by luminance different from the base in the source image, sorting them by respective display colors and generating the image data of the main image for the respective colors, a display color candidate extracted from the source image is integrated with a display color candidate nearby on the condition that they are included in the same division space and the display color is decided for each main image part. At the time, in the case that the plurality of display color candidates satisfying the integration condition exist in both of a prescribed achromatic color region and a chromatic color region on the outer side, the display color candidates existing separately in both regions are not integrated with each other and are adopted as the display colors respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing apparatus for generating a so-called multi-layer image by dividing a color image into a plurality of layers, and an image reading apparatus and image processing method including the image processing apparatus. And an image processing apparatus including the image processing apparatus, the image reading apparatus, and the image processing method including the image processing apparatus in which the main image is sorted for each display color and stored in a file in a separate layer. .

  In order to digitize documents, a method of reading a document with a scanner and converting it to image data has become widespread, and when distributing a document created with document creation software on a computer, it can be viewed without any problems at the distribution destination. It is desirable to convert the document into image data, and there are various compression methods for reducing the data size in order to save the storage device capacity and shorten the communication time. It's being used.

In particular, in the case of a color document, the reproduction image quality may deteriorate due to the color compression process due to the difference in brightness between the character that is usually drawn at low brightness and its surroundings. There is a known technique in which a character image with a different drawing color is stored for each display color and stored in a file on a separate layer for the compression processing using different compression methods for the image and the background image (patent) Reference 1). In particular, in this technology, in order to keep the file size small, character regions that are regarded as the same color in a predetermined color range are integrated to increase the compression efficiency.
JP 2003-18413 A

  However, in the case where the colors included in the predetermined range are integrated as the same color as in the conventional technique, the compression efficiency can be improved by reducing the color by setting a large range to be integrated into one color. However, the impression of viewing may change due to the integration of distant colors, especially in the near-achromatic color region, since slight changes in saturation can be easily identified by human color vision, the original image In the above, a color that is clearly visible as a chromatic color may change to an achromatic color or a color that cannot be visually recognized, resulting in a deterioration in image quality such that the viewed impression is greatly different from the original image.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is to generate a color-specific main image for multi-layering a color image. An image processing apparatus configured to avoid a deterioration in image quality in which an impression seen in a color region close to an achromatic color is largely changed from an original image due to human color vision characteristics in color reduction by color integration, and An object of the present invention is to provide an image reading apparatus and an image processing method provided with the same.

  In order to solve such a problem, in the image processing apparatus according to the present invention, as shown in claim 1, a main image drawn with a luminance different from the background is extracted from the original image and the main image is extracted from the original image. Main image generation means for generating image data of the main image for each color by sorting for each display color, and a portion in the original image corresponding to the main image is filled with a required fill color based on the image data of the surrounding pixels A main image generating unit that generates image data of an image, and an image compressing unit that compresses each image data of the main image and the base image obtained thereby by different compression methods; However, the display color candidates extracted from the original image for each main image part are integrated with the display color candidates in the vicinity thereof according to a predetermined integration condition to determine the display color. When there are a plurality of display color candidates that satisfy the integration condition in both the area and the chromatic color area outside the area, the display color candidates existing separately in both areas are not integrated, The display color is adopted separately.

  According to this, if the achromatic color region is appropriately set, it is possible to avoid a deterioration in image quality in which a color that can be easily recognized as a chromatic color on the original image changes to a color that can only be recognized as an achromatic color.

  In this case, the achromatic region may be a region that is centered on a straight line that is an achromatic color in the color space and that is defined by a predetermined threshold as a distance to the boundary.

  In addition, in the process of extracting display color candidates from the original image, a group of pixels that continuously constitute the main image, that is, each continuous region of pixels that become black pixels on a binary image obtained by binarizing the main image. For example, a representative color may be obtained, for example, an average color obtained by averaging a plurality of pixel values may be obtained and used as a display color candidate.

  In the image processing device, as described in claim 2, the main image generation means includes a plurality of display color candidates as one of the integration conditions that the color space is included in one of the divided spaces. The display color candidates are determined as display colors according to the priority order set according to the number of pixels for the display color candidates for each divided space. At this time, a predetermined color centered on the display color candidates is determined. If there is a display color with a high priority in the similar region, the display color candidates can be integrated with the display color. According to this, since the color of the main image drawn in the same color as one character is in the vicinity of the boundaries of the plurality of divided spaces, even if a plurality of display color candidates that should originally be one are set, the similar region It can be integrated on the condition that it is within, and the problem that the display color increases unnecessarily can be avoided.

  In this case, the similar region is a region in which the distance to the boundary is defined by a predetermined threshold with the target display color candidate as the center.

  In the image processing device, as shown in claim 3, the main image generation unit integrates display color candidates in the achromatic color region and integrates display color candidates in the chromatic color region. Thus, the integration process is performed using the similar areas having different sizes, and the similar area for the achromatic color area is set to be larger than the similar area for the chromatic color area. According to this, in the chromatic color area, the impression seen by the integration of distant colors changes greatly, but in the achromatic color area, the impression seen only by the gradation change does not change much even when the distant colors are integrated. By reducing the color by using a large similar area in the achromatic color area, it is possible to increase the compression efficiency while suppressing the deterioration of the image quality.

  According to a fourth aspect of the present invention, there is provided an image reading apparatus comprising the image processing apparatus and original reading means for reading a color image of an original, and based on original image data acquired by the original reading means. Thus, the image processing apparatus performs a required process and outputs a multilayer image file.

  In the image processing method according to the present invention, as shown in claim 5, a main image drawn with a luminance different from that of the background is extracted from the original image, and the main image is sorted by display color. A step of generating image data for each color, a step of generating a background image image data by painting a portion in the original image corresponding to the main image with a required fill color based on the image data of the surrounding pixels, and Compressing each image data of the obtained main image and background image by mutually different compression methods, and generating image data of the main image for each color from the original image for each main image portion The extracted display color candidates are integrated with the display color candidates in the vicinity thereof in accordance with a predetermined integration condition to determine the display color. At this time, the predetermined achromatic color region and the outside thereof are determined. When there are a plurality of display color candidates that satisfy the integration condition in both the chromatic color area, the display color candidates that exist separately in both areas are not integrated, and are separately displayed as display colors. Adopted.

  According to this, if the achromatic color region is appropriately set, it is possible to avoid a deterioration in image quality in which a color that can be visually recognized as a chromatic color on the original image changes to a color that can only be visually recognized as an achromatic color.

  As described above, according to the present invention, in order to improve the compression efficiency by subtractive color, by setting a large range to be integrated into one color, the impression seen in the color region close to the achromatic color is greatly changed from the original image. Thus, a significant effect can be obtained in reducing the data size by increasing the compression efficiency while suppressing the deterioration of the image quality.

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

  FIG. 1 is a block diagram showing a schematic configuration of a multifunction machine to which an image processing apparatus according to the present invention is applied. This multi-function machine includes a CCD 1 that reads an image of a document, a read data processing unit 2 that processes image data from the CCD 1 so as to obtain an appropriate read result, and a read data processing unit that obtains an appropriate print result. 2 has a print data processing unit 3 that processes image data from 2, and a printer engine 4 that records an image on recording paper based on the image data from the print data processing unit 3, and copies the original image onto the recording paper. It has a copy function.

  In addition, this multifunction device has a scanner function for reading an image of a document and creating an output image file, and image data obtained through the CCD 1 and the read data processing unit 2 is sent to the multi-layer image generation unit 5. In this case, the read image data is separated into a base image and a character image, compressed by a different compression method, and stored in a PDF (portable document format) file format (multi-layer image file). ) Is created.

  Furthermore, this multifunction device has a data conversion function for creating a multi-layer image file from print data of a document created by document creation software on a computer such as a PC, and print data in a page description language such as a postscript. Is received by the network control unit 6, and the print data is converted into RGB image data by the data conversion unit 7 and then sent to the multi-layer image generation unit 5 to create a multilayer image file.

  The read data processing unit 2 includes an A / D / offset adjustment unit 11 that performs A / D conversion and offset adjustment of the output signal of the CCD 1, a shading / black correction unit 12 that corrects sensitivity unevenness of the CCD 1, and a line sensor. The line-to-line correction unit 13 corrects a shift in the sub-scanning direction caused by the CCD 1 and the gamma correction unit 14 performs gamma correction according to the characteristics of the CCD 1.

  The print data processing unit 3 includes a color conversion unit 16 that performs color space conversion of RGB image data to CMYK image data, a scaling unit 17 that expands and contracts to an image size corresponding to the output resolution of the printer engine 4, and a printer. A printer gradation correction unit 18 that corrects gradation so as to conform to the output characteristics of the engine 4 and characters in order to appropriately perform the processing of the color conversion unit 16 and the printer gradation correction unit 18 according to the characteristics of the image. And an image area determination unit 19 for detecting an area such as a photograph.

  FIG. 2 is a block diagram illustrating a configuration of the multi-layer image generation unit illustrated in FIG. The multi-layer image generation unit 5 extracts a main image such as a character or a line drawing figure drawn with a luminance different from that of the background image (background image) in the color original image from the original image (main image generation unit). 21, a background image generation unit (background image generation means) 22 that generates a background image by painting a portion of the original image corresponding to the main image with a predetermined fill color, and the main image and the background image obtained thereby A main image compression unit (image compression unit) 23 and a background image compression unit (image compression unit) 24 for compressing the image by different compression methods, and a plurality of compressed image data of the main image and the background image obtained thereby. And a file generation unit 25 for allocating the files to a file.

  The main image generation unit 21 includes a luminance generation unit 31 that calculates luminance for each pixel from RGB image data, and a binarization process that binarizes the luminance image obtained thereby based on a predetermined threshold value. An image for extracting a main image such as a character or a graphic based on the area information obtained by the area determination unit 33 for determining an area such as a character or a graphic in the binary image obtained thereby; An extraction unit 34, a main image color extraction unit 35 that extracts a display color at the time of reproduction of the main image obtained thereby from the original image, and stores the main image in a file in a separate layer for each display color obtained thereby In order to do this, it has a color-by-color layer dividing unit 36 that creates data of main images by color.

  The area determination unit 33 determines each area of the character in the binary image, the table separated by the ruled line, the figure drawn by the line drawing, and the bitmap image (photograph, etc.), and the binary of each area obtained here Based on the area information regarding the position (coordinates) on the image, the image extracting unit 34 extracts characters, ruled lines, and line drawing figures as main images. In the character area, a process of cutting out an image of one character unit through line recognition is performed. In the table area, the table structure may be recognized and a ruled line image and a cell unit image may be cut out.

  The main image compression unit 23 compresses main image data such as characters and line drawing figures by a compression method suitable for binary image compression, for example, MMR or JBIG. In the background image compression unit 24, the data of the background image is compressed by a compression method with excellent multi-value image compression efficiency, for example, JPEG. The compressed image data of the main image and the background image obtained in this manner is filed as a separate layer in the file generation unit 25, so that when the original image is directly JPEG compressed, the luminance is lower than that of the surrounding background portion. It is possible to avoid the occurrence of mosquito noise in the surrounding background portion due to the main images such as characters and line drawings drawn on the screen.

  In assigning the compressed data of the main image to the color-specific layers, a predetermined number (for example, eight) of color-specific layers is set in advance, and the main image color extracting unit 35 determines the number of colors corresponding to the number of layers. Therefore, a color reduction process for unifying the approximate colors is performed. The main image color extraction unit 35 generates color palette information indicating the correspondence between the display color of the main image (binary image) separated by color and the identification number of each color layer. The file generation unit 25 stores the multi-layer image file.

  The base image generation unit 22 represents a portion of the binary main image obtained by the image extraction unit 34 of the main image generation unit 21, that is, a portion in the original image corresponding to a pixel that is a black pixel on the binary image. A background image is generated by painting with a paint color similar to the surrounding color, and a paint color extracting unit 37 that extracts a paint color for painting from the original image and an image extracting unit 34 of the main image generating unit 21. A paint processing unit 38 is provided for painting a portion in the original image corresponding to the image line part of the obtained main image with the paint color obtained by the paint color extracting unit 37.

  The fill color extraction unit 37 determines the fill color with reference to the pixel values of the part in the original image corresponding to the non-image line part around the image line part of the main image obtained by the image extraction unit 34. In particular, here, after the RGB image data is converted to YCbCr image data, the luminance component value Y of the fill color is determined based on the luminance component value of the pixel in the portion of the original image corresponding to the non-image portion. On the other hand, the color difference component values (chromaticity component values) Cb · Cr of the fill color are preset to Cb = Cr = 128 when the intermediate value, for example, the color difference component value is expressed in 256 levels, and the fill color is It becomes achromatic.

  In the background image compression unit (image compression means) 24, the data of the background image is JPEG-compressed, and in this JPEG compression, downsampling for greatly compressing the color difference component value with respect to the luminance component value is performed. The sampling ratio Y: Cb: Cr of the luminance component value Y and the color difference component values Cb · Cr may be any one of 4: 1: 1, 4: 2: 2, 4: 2: 0.

  FIG. 3 is a conceptual diagram showing a processing procedure in the multilayer image generation unit shown in FIG. A binary image obtained by binarizing the original image is obtained through the luminance generation unit 31 and the binarization processing unit 32 of the main image generation unit 21, and further, the characters, tables, and figures are obtained through the region determination unit 33 and the image extraction unit 34. The image data of the main image for each area type is obtained, and the image of the character area is segmented in units of one character by a rectangle circumscribing the character in the binary image to obtain a character image for each character.

  Extraction of the color of the main image performed by the main image color extraction unit 35 of the main image generation unit 21, and extraction of the fill color and fill processing performed by the fill color extraction unit 37 and the fill processing unit 38 of the base image generation unit 22. Is performed for each block of 8 × 8 pixels, which is a processing unit in JPEG compression processing.

  First, in the main image color extracting unit 35 of the main image generating unit 21, the color of the pixel having the same coordinate as that of the pixel constituting the image line unit which is a black pixel on the binary image is acquired from the data of the multi-valued image (original image). Then, based on each pixel value on the multi-valued image, a color (for example, red) for displaying the image line portion of the main image is determined. Then, the color layer dividing unit 36 of the main image generating unit 21 performs a process of distributing the main image for each display color obtained by the main image color extracting unit 35 and creating data of the main image for each color.

  In addition, the fill color extraction unit 37 of the base image generation unit 22 has luminance component values of pixels having the same coordinates as the pixels constituting the non-image part that is a white pixel around the image line part that is a black pixel on the binary image. Is obtained from the data of the multivalued image subjected to the YCbCr color system conversion, the average value of the luminance component values for each pixel on the multivalued image is calculated, and the average luminance component value and the intermediate value (128) are calculated. The fill color is determined based on the color difference component value set in advance. For example, if the portion in the multi-valued image corresponding to the non-image area of the binary image is blue, the portion corresponding to the image area of the binary image is surrounded by the background image obtained by the fill processing unit 38. The color scheme is filled with gray with the same brightness as the blue color.

  When acquiring the display color of the main image, the display color is determined for a plurality of pixels selected according to an appropriate rule, not for all the pixels constituting the image line portion in the processing block. It is good to do. Similarly, when obtaining the fill color of the background image, the fill color may be determined for a plurality of pixels selected according to an appropriate rule from the pixels constituting the non-image portion. In addition, pixels located on the outer periphery of the character image for each character can be used as a reference for determining the fill color of the base image.

  4 and 5 are flowcharts showing a processing procedure in the multilayer image generation unit shown in FIG. Here, an example in which characters are used as a main image is shown.

  First, image data of an RGB original image stored in the memory is acquired in the main image generation unit 21 (step 101), and then image data based on YCbCr is generated by color system (color space) conversion processing (step 102). After the luminance image by the luminance component value Y is created by the luminance generation unit 31, the binarization processing unit 32 performs a process of binarizing the luminance image (step 103). A layout analysis process for detecting areas such as characters and graphics in the binary image is performed by the area determination unit 33, and attributes relating to the area type and the position (coordinates) of the area on the original image are set for each area. Is created (step 104).

  Next, the process proceeds to a process of acquiring an image of one character unit (steps 105 to 108). Here, a process of cutting out a character image for each character from the binary image in the character region is first performed by the image extraction unit 34 (step 106) Next, a process of adding the storage address of the character image for each character cut out to the area list is performed (step 107).

  Next, the display color of the character image is acquired for each character, and the process proceeds to the step of compressing the image by assigning it to the character layer by color (steps 109 to 116). Here, the character image belonging to the character region is first referred to the region list. The processing for obtaining the coordinates for each processing block is performed, and a character list describing the information regarding the processing block thus obtained is created (step 110). Then, the process of acquiring the display color of the character image in units of processing blocks described in the character list is performed by the main image color extraction unit 35 (step 112), and then the process of sorting the image in units of processing blocks for each display color is performed. This is performed by the color-specific layer dividing unit 36 (step 113). Further, when the display color acquisition and sorting process for all characters belonging to the target character area is completed (step 114), the main image compression unit 23 performs a process of compressing the binary image for each display color (step 115). ).

  Next, as shown in FIG. 5, the process proceeds to a process (steps 117 to 123) of obtaining and painting the fill color of the background image in units of processing blocks. Here, first, information on the processing block for each character is obtained as described above. After the described character list is created (step 118), a process of acquiring a fill color for each processing block described in the character list is performed by the fill color extracting unit 37 (step 120), and then the acquired fill color is used. The painting process is performed by the painting processing unit 38 in units of processing blocks (step 121).

  When the filling process for one page is completed (step 123), the background image compression unit 24 performs the sub-sampling of the filled multi-value image and JPEG compression (steps 124 and 125).

  When the compressed data of the character image and the background image is acquired in this way, the process proceeds to the process of creating the multilayer image file, and the process of adding the header information to each compressed data of the character image and the background image and writing to the file is performed. This is performed by the generation unit 25 (steps 126 and 127).

  6 and 7 are conceptual diagrams showing an outline of the character color extraction process shown in FIG. In particular, FIG. 7 shows an RB plane for convenience of explanation. In the main image color extraction unit 35 of the main image generation unit 21, in order to limit the number of display colors to a predetermined value, the display color candidates extracted from the original image for each main image part are integrated with the display color candidates in the vicinity thereof. In particular, here, one display color is set in principle for a divided space obtained by dividing the RGB color space at equal intervals, and a plurality of display color candidates exist in one divided space (integration condition) ) Is performed to integrate the plurality of display color candidates into one.

  In the process of extracting display color candidates from the original image, a pixel group that continuously constitutes the main image, that is, a continuous region of pixels that become black pixels on the binary image obtained by binarizing the main image is represented. A color is obtained and used as a display color candidate. At this time, the average value of a plurality of pixel values constituting a continuous area of black pixels is calculated, that is, the average value obtained by calculating the average value for each RGB by averaging the RGB values of each pixel is representative. Color should be used. Similarly, in the integration process in the case where a plurality of display color candidates exist in one divided space, similarly, the average color obtained by calculating the average value of the pixel values of the plurality of display color candidates is displayed in the corresponding divided space. Color candidates can be used.

  In the example of FIG. 6, the number of divisions is set to 4 for each RGB component value, and the total number of division spaces is 4 × 4 × 4 = 64, but this division number depends on the required compression rate and the like. It is possible to set the number of divisions more appropriately than this, and for example, the number of divisions may be 16 for each RGB component value. In this case, the total number of division spaces is 16 × 16 ×. 16 = 4096.

  Furthermore, here, a straight line R = G = B connecting white (R, G, B) = (0, 0, 0) and black (R, G, B) = (255, 255, 255) is the center. An area of a predetermined width is defined as an achromatic color area, and the integration process is separately performed for the display color candidates in the achromatic color area and the display color candidates in the chromatic color area outside the achromatic color area. When there are a plurality of display color candidates that satisfy the integration condition of the divided space in both the chromatic color area and the outer chromatic color area, the display color candidates that exist separately in both areas are integrated. Instead, they are adopted separately as display colors.

  Therefore, in the achromatic color division space including the achromatic color region, two display colors of the achromatic color and the chromatic color can be set, and when there are a plurality of display color candidates in the achromatic color region in the achromatic color division space, In addition, when there are a plurality of display color candidates in the chromatic color region in the achromatic color division space, the integration process is performed for each. On the other hand, in the chromatic color division space that does not include the achromatic color region, one display color is set, and when there are a plurality of display color candidates, their integration processing is performed.

  The achromatic region is a region centered on a straight line R = G = B, which is an achromatic color in the color space, and the distance to the boundary is defined by a predetermined threshold value. The achromatic color region is the RGB color space. The threshold value that defines the size (radius) of the cylinder having the straight line R = G = B as the center line is set to 15 when the RGB color component values are represented by values of 0 to 255, for example. Has been.

  Further, here, the display color candidate is determined as the display color according to the priority set in accordance with the number of pixels with respect to the display color candidate for each divided space, and at this time, in the similar region centered on the display color candidate. When there is a display color with a high priority, the display color candidate is integrated with the display color. In particular, when the display color candidates in the achromatic color area are integrated and when the display color candidates in the chromatic color area are integrated, integration processing is performed using similar areas of different sizes, and for the achromatic color area. The similar region is set larger than the similar region for the chromatic color region.

  The similar region is a region in which the target display color candidate is the center and the distance to the boundary is defined by a predetermined threshold. The similar region is a sphere centered on the display color candidate and has a large size. The threshold value defining the thickness (radius) is set to 96 for achromatic colors and 32 for chromatic colors, for example.

  In the example of FIG. 7, first, the first display color candidate is determined as the display color. And since this first display color candidate is a chromatic color, the second display color candidate is an achromatic color, so both are in the same divided space but are not integrated, The second display color candidate is also determined as the display color. On the other hand, since the third display color candidate is a chromatic color, the necessity of integration is determined by the similar region. Here, the first display color candidate is ranked first in the similar region centered on the third display color candidate. Since there are display color candidates, the third display color candidate is integrated with the first display color candidate with the highest priority in the prior order.

  On the other hand, for example, in the conventional method of averaging and integrating the display color candidate values, the first and second display color candidates are integrated into their average colors (achromatic colors), and the average color The third priority display color candidate having a low priority is integrated into the display color, and this causes a disadvantage that neither the first or third display color candidate of the chromatic color is adopted as the display color. With this configuration, since the first display color candidate of the chromatic color is adopted as the display color, it is possible to avoid deterioration in image quality in which the color changes from the original image.

  As described above, display colors are determined by integrating display color candidates extracted from the original image for each main image portion (continuous region of black pixels) according to a predetermined integration condition. The number is limited to a predetermined number, for example, 12 for each region such as a character detected by the image area determination unit 19, a table delimited by ruled lines, and a figure drawn by a line drawing. When the number of display colors reaches a predetermined number, the process ends. At this time, display color candidates that are not adopted as display colors are discarded, but according to the priority set according to the number of pixels as described above. Since the display color candidate is determined as the display color, it is possible to avoid image quality deterioration that greatly changes the viewed impression.

  FIG. 8 is a flowchart showing a processing procedure of character color extraction shown in FIG. This character color extraction process is performed by the main image color extracting unit 35 of the main image generating unit 21 shown in FIG. 2, and the number of pixels is large with respect to each continuous area of black pixels. The representative colors of the numbered labeling data are registered as display color candidates, and the display color candidates are sequentially determined as display colors based on the priority order according to the number of pixels. At this time, approximate colors are determined according to predetermined integration conditions. Are integrated into one display color, and the display color is determined in a range not exceeding a predetermined number.

  First, a process of decomposing a character block into a plurality of labeling data is performed (step 201), and then a process of obtaining a representative color of the labeling data by averaging the values of each pixel included in the labeling data (step 201). Step 202). Based on a predetermined threshold value, it is determined whether or not the representative color of the labeling data is an achromatic color, that is, whether or not it is in the achromatic color region shown in FIG. 7 (step 203). Then, a process of registering the representative color of the labeling data as an achromatic color candidate in the corresponding achromatic color divided space is performed (step 204), and if it is not an achromatic color, that is, if it is a chromatic color, the representative color of the labeling data Is registered as a chromatic color display color candidate in the corresponding achromatic or chromatic color divided space (step 205).

  Next, the number of pixels included in the divided space corresponding to the display color candidates is counted, and the process of rearranging the display color candidates in the descending order of the number of pixels is performed (step 206). Next, when there are a plurality of display color candidates in each divided space, a process for obtaining a representative display color candidate for each divided space is performed by averaging the values of the plurality of display color candidates ( Step 207). Here, in the achromatic color division space, averaging processing is performed separately for the achromatic color region and the chromatic color region, and when the display color candidates for the labeling data are divided into both regions, the representative display color is displayed. Two candidates are set.

  Next, display color candidates are selected according to the priority order. If there are unprocessed display color candidates at this time (step 208), whether or not the determined number of display colors is less than a predetermined threshold value. Is determined (step 209), and if it is determined that the number of display colors is less than the threshold value, it is determined whether or not there is a determined display color (step 210). If there is no display color, that is, the first display color candidate with the highest priority, the display color candidate is determined as the display color (step 211), and the process proceeds to the next display color candidate process. (Steps 208-210).

  If it is determined in step 210 that the determined display color is present (step 210), it is determined whether the target display color candidate is an achromatic color. 7 is determined (step 212). If the display color candidate is an achromatic color, the target display is selected from the determined achromatic display colors. A process for searching for a color candidate that is close to the color candidate is performed (step 213). If the display color candidate is not an achromatic color, that is, if it is a chromatic color, the display color candidate that has been determined is selected as a target display color candidate. A process for searching for a nearby object is performed (step 214).

  Next, whether or not the determined display color found by the search process (steps 213 and 214) is in a similar region centered on the target display color candidate is determined for achromatic color and chromatic color. (Step 215). If it is determined that there is no display color already determined in the similar region of the target display color candidate, the display color candidate is set as the display color. Processing to determine is performed (step 216). On the other hand, if it is determined that there is a determined display color in the similar region of the target display color candidate, processing for deleting the display color candidate is performed (step 217).

  When the above processing is performed for each display color candidate according to the priority order, and it is determined in step 208 that there is no unprocessed display color candidate, it is determined that there is no unprocessed display color candidate. The process is terminated. In the determination of whether or not the determined display color number is less than the predetermined threshold value (step 209), the display color number is not less than the predetermined threshold value, that is, the display color number is set to the predetermined threshold value. If it is determined that it is not possible to register any more display colors, the process ends even if there are unprocessed display color candidates remaining.

  FIG. 9 is a flowchart showing a processing procedure of character image color separation shown in FIG. This character image color separation processing is performed by the color layer division unit 36 of the main image generation unit 21 shown in FIG. 2, and the display color acquired by the character color extraction processing shown in FIG. Each time, the labeling data is sorted based on the representative color of the labeling data, and the image data of the main image stored in the file in another layer is generated for each color.

  First, a process of decomposing a character block into a plurality of labeling data is performed (step 301), then it is determined whether or not unprocessed labeling data exists (step 302), and there is unprocessed labeling data. For example, it is determined whether or not the representative color of the labeling data is an achromatic color (step 303). If the representative color is an achromatic color, the most representative color of the labeling data is selected from the achromatic display colors. A process of searching for a close object is performed (step 304), and the labeling data is drawn with the display color acquired thereby (step 305).

  On the other hand, if it is determined whether the representative color of the labeling data is an achromatic color (step 303), it is determined that the representative color of the labeling data is not the achromatic color, that is, if it is determined to be a chromatic color, the most representative color of the labeling data. A process of searching for a close one is performed (step 306), and then the display color found by the search process is compared with the representative color of the labeling data to determine whether or not both are within a predetermined threshold value. (Step 307). If it is determined that the value is within the threshold value, the labeling data is drawn with the display color found by the search process (step 306) (step 305).

  On the other hand, if it is determined that the display color found by the search process (step 306) is not within the threshold value in the determination based on the threshold value (step 307), the process of removing the labeling data from the list is performed. This is done (step 308), thereby abandoning drawing of the corresponding labeling data as the main image, and the main image portion corresponding to this is displayed as the background image. Thereby, it is possible to avoid drawing with a display color whose color tone is greatly separated. When the processing of the labeling data focused in this way is completed, the process proceeds to the processing of the next labeling data, and the same processing is repeated for all the labeling data.

  An image processing apparatus, an image reading apparatus provided with the image processing apparatus, and an image processing method according to the present invention provide a human color vision in color reduction by color integration when generating a color-specific main image for multi-layering a color image. Due to the above characteristics, it has the effect of avoiding the image quality degradation that the impression seen in the color area close to achromatic color greatly changes from the original image, and the color image is divided into multiple layers and filed. The present invention is useful as an image processing apparatus that generates a so-called multi-layer image, an image reading apparatus including the image processing apparatus, and an image processing method.

1 is a block diagram showing a schematic configuration of a multifunction machine to which an image processing apparatus according to the present invention is applied. The block diagram which shows the structure of the multi-layer image production | generation part shown in FIG. The conceptual diagram which shows the point of the process in the multilayer image generation part shown in FIG. The flowchart which shows the procedure of the process in the multilayer image generation part shown in FIG. The flowchart which shows the procedure of the process in the multilayer image generation part shown in FIG. Conceptual diagram showing an outline of the character color extraction process shown in FIG. Conceptual diagram showing an outline of the character color extraction process shown in FIG. The flowchart which shows the procedure of the character color extraction process shown in FIG. FIG. 4 is a flowchart showing the procedure of character image color separation processing shown in FIG.

Explanation of symbols

5 Multilayer image generation unit 21 Main image generation unit (main image generation means)
22 Background image generation unit (background image generation means)
23 Main image compression unit (image compression means)
24 Base image compression unit (image compression means)
37 Fill Color Extraction Unit 38 Fill Processing Unit

Claims (5)

Main image generation means for extracting a main image drawn with a luminance different from that of the background in the original image from the original image and distributing the main image for each display color to generate image data of the main image for each color;
A background image generation means for generating a background image image data by painting a portion in the original image corresponding to the main image with a required fill color based on image data of surrounding pixels;
Image compression means for compressing each image data of the main image and the background image obtained thereby by different compression methods;
The main image generation means determines the display color by integrating the display color candidates extracted from the original image for each main image portion with the display color candidates in the vicinity thereof according to a predetermined integration condition. When there are a plurality of display color candidates that satisfy the integration condition in both the predetermined achromatic color area and the chromatic color area outside the predetermined achromatic color area, the display color candidates that exist separately in both areas are integrated. An image processing apparatus characterized in that the display color is adopted separately.   The main image generation means integrates a plurality of display color candidates into one as a result of being included in one of the divided spaces obtained by dividing the color space at equal intervals, and the display color candidates for each divided space Display color candidates are determined as display colors according to the priority order set according to the number of pixels. At this time, a display color with a high priority order exists in a predetermined similar region centering on the display color candidates. 2. The image processing apparatus according to claim 1, wherein the display color candidates are integrated with the display color.   Integration processing using the similar regions having different sizes when the main image generation unit integrates display color candidates in the achromatic color region and when integrates display color candidates in the chromatic color region The image processing apparatus according to claim 2, wherein the similar region for the achromatic color region is set to be larger than the similar region for the chromatic color region.   An image processing apparatus according to any one of claims 1 to 3 and an original reading unit that reads a color image of an original, and the image processing apparatus includes the original image data acquired by the original reading unit. An image reading apparatus in which a required process is performed and a multilayer image file is output. Extracting a main image drawn with a luminance different from the background in the original image from the original image and distributing the main image for each display color to generate image data of the main image for each color;
Generating a background image image data by painting a portion in the original image corresponding to the main image with a required fill color based on the image data of the surrounding pixels;
Compressing each image data of the main image and the background image obtained thereby by different compression methods,
In the step of generating image data of the main image for each color, a display color candidate extracted from the original image for each main image portion is integrated with a display color candidate in the vicinity thereof according to a predetermined integration condition to determine a display color. In this case, if there are a plurality of display color candidates that satisfy the integration condition in both the predetermined achromatic color area and the chromatic color area outside the predetermined achromatic color area, the display color is divided into both areas. An image processing method characterized in that display color candidates to be used are not integrated but are separately adopted as display colors.

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