JP2008066950A - Image color deciding device, image color deciding method, and image color deciding program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform processing suitable to features of a document even when an image associated with the document is an achromatic color image. <P>SOLUTION: When deciding that the image is a monochromatic image, a mode deciding unit 152 further decides features of the document by using decision results of a block decision unit 148 which decides color classifications that respective blocks obtained by longitudinally and laterally dividing the image associated with the document belong to decide which of a white-paper document, a gray document, and a black-and-white document the document is. The mode decision unit 152 sets the processing mode of a digital multifunction apparatus 1 to a white-paper mode when deciding that the document is a white-paper document, sets the processing mode of the digital multifunction apparatus 1 to a mode suitable to a gray document when deciding that the document is the gray document, and sets the processing mode of the digital multifunction apparatus 1 to a mode suitable to a black-and-white document when deciding that the document is the black-and-white document. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image color determination device, an image color determination method, and an image color determination program.

  An electrophotographic color copying machine that reads an original and reproduces an image on a recording sheet is usually provided with an image forming engine of four colors of yellow, magenta, cyan, and black, and repeats image formation on the recording sheet four times. This realizes color copying. However, when the image relating to the document is an achromatic image, it is wasteful in terms of copying time and copying cost to operate all four color image forming engines to form an image on recording paper. For this reason, it is automatically determined whether or not the image relating to the original is an achromatic image, and when the image can be regarded as an achromatic image, only the black image forming engine is operated to operate on the recording paper. It is desirable to form an image on

  Note that Patent Document 1 is a prior art document relating to a technique for determining whether an image is an achromatic image.

Japanese Patent Publication No.8-10901

  However, in the prior art, it can be determined whether or not the image related to the original is an achromatic image, but when the image related to the original is an achromatic image, the color copier performs processing suitable for the characteristics of the original. I couldn't.

  The present invention has been made to solve this problem, and an image processing apparatus such as a color copier can perform processing suitable for the characteristics of an original even if the image related to the original is an achromatic image. The purpose is to be able to.

  In order to solve the above-described problem, the invention of claim 1 includes a luminance classification determination unit that determines whether each of blocks obtained by dividing an image related to a document belongs to a luminance classification of white, gray, or black, An image color determination apparatus comprising: a determination unit that determines a processing mode of the image using a determination result of the luminance classification determination unit.

  The invention according to claim 2 is characterized in that the determining means sets the processing mode of the image to the first mode when all the blocks belong to the white luminance classification. It is a determination device.

  The invention according to claim 3 is characterized in that the determining means sets the processing mode of the image to the second mode when the number of blocks belonging to the gray luminance classification is equal to or greater than a reference value. Alternatively, the image color determination apparatus according to claim 2.

  The invention according to claim 4 is characterized in that the determining means sets the processing mode of the image to a third mode when the number of blocks belonging to the gray luminance division is smaller than a reference value. An image color determination apparatus according to claim 3.

  According to a fifth aspect of the present invention, there is provided averaging means for averaging pixel data for each pixel set including a plurality of pixels, and pixel data averaged by the averaging means is assigned to any of white, gray, and black luminance categories. Pixel data determination means for determining whether the block belongs, and the luminance classification determination means uses the determination result of the pixel data determination means, and each of the blocks belongs to one of white, gray, and black luminance classifications 5. The image color determination apparatus according to claim 1, wherein the image color determination apparatus is configured to determine whether the

  The invention of claim 6 further comprises copy means for copying an image from a document to a recording medium, wherein the number of pixels included in the pixel set is determined based on a scaling factor at the time of copying. 5. The image color determination device according to 5.

  The invention according to claim 7 further includes conversion means for converting the resolution of the image, and the luminance classification determination means is configured such that each of the blocks obtained by dividing the image before the resolution is converted by the conversion means is white. 7. The image color determination apparatus according to claim 1, wherein the image color determination apparatus determines which one of the brightness classifications gray, gray, and black belongs.

  The invention according to claim 8 includes unit data determination means for determining whether or not unit data that is a constituent unit of image data relating to the image belongs to a gray luminance classification, and the number of unit data belonging to the gray luminance classification. Counting means for counting the number of gray unit data, and the brightness classification determining means determines that the block belongs to the gray brightness classification when the number of gray unit data exceeds a first threshold, and the number of gray unit data Is less than the first threshold and greater than the second threshold, it is determined that the block belongs to the black luminance category, and when the gray unit data number is equal to or less than the second threshold, it is determined that the block belongs to the white luminance category. The image color determination device according to claim 1, wherein the image color determination device is a device for determining image color.

  According to a ninth aspect of the present invention, there is provided unit data determination means for determining whether or not unit data as a constituent unit of image data relating to the image belongs to a gray luminance category and whether to belong to a black luminance category, gray data And counting means for counting the number of gray unit data that is the number of unit data belonging to the luminance classification and the number of black unit data that is the number of unit data belonging to the black luminance classification, and the luminance classification determining means If the number of unit data exceeds the first threshold and the number of black unit data exceeds the second threshold, it is determined that the block belongs to the black luminance classification, the number of gray unit data exceeds the first threshold, and the number of black unit data is the second. If the threshold is less than or equal to the threshold, the block is determined to belong to the gray luminance category. If the number of gray unit data is equal to or less than the first threshold and the number of black unit data exceeds the second threshold, the block is determined to belong to the black luminance category. , 8. The block according to claim 1, wherein when the number of ray unit data is equal to or less than a first threshold and the number of black unit data is equal to or less than a second threshold, it is determined that the block belongs to a white luminance category. This is an image color determination device.

  The invention according to claim 10 determines whether the image is an achromatic color image by using a color classification determination means for determining a color classification to which each block belongs, and a determination result of the color classification determination means. 10. An achromatic color determining unit, further comprising: determining a processing mode of the image when the achromatic color determining unit determines that the image is an achromatic image. The image color determination apparatus according to any one of the above.

  According to the eleventh aspect of the present invention, there is provided a luminance classification determining step for determining whether each of the blocks obtained by dividing the image relating to the original document belongs to a luminance classification of white, gray or black, and determination of the luminance classification determining step And a determination step of determining a processing mode of the image using a result.

  According to a twelfth aspect of the present invention, there is provided a luminance classification determination procedure for determining whether each block obtained by dividing an image relating to a document belongs to a luminance classification of white, gray, or black, and determination of the luminance classification determination procedure An image color determination program that causes a computer to execute a determination procedure for determining a processing mode of the image using a result.

  According to the first to twelfth aspects of the present invention, even if the image relating to the document is an achromatic image, processing suitable for the characteristics of the document can be performed.

  According to the second aspect of the present invention, it is possible to perform processing suitable for a blank original in the first mode.

  According to the invention of claim 3, processing suitable for a gray document can be performed in the second mode.

  According to the invention of claim 4, it is possible to perform processing suitable for a black and white document in the third mode.

  According to the invention of claim 5, the influence of false color can be eliminated.

  According to the invention of claim 6, it is possible to effectively eliminate the influence of false color due to zooming.

  According to the invention of claim 7, the determination of the processing mode is not affected by the resolution conversion.

  According to the invention of claim 8, the image color determination device can be simplified.

  According to invention of Claim 9, an image color determination apparatus can be simplified.

  According to the tenth aspect of the present invention, it is possible to automatically determine whether or not an image relating to an original is an achromatic image and to perform processing suitable for the characteristics of the original.

<1 Overall configuration of digital multifunction device>
FIG. 1 is a block diagram showing an overall configuration of a digital multi-function peripheral 1 according to a preferred embodiment of the present invention. The digital multi-function peripheral 1 is also called MFP (Multi Function Peripherals) and has a plurality of functions such as a facsimile function, a copy function, a scan function, and a print function.

  As shown in FIG. 1, the digital multifunction peripheral 1 includes a CPU 102, a ROM 104, and a RAM 106. The ROM 104 stores a program PRG such as firmware of the digital multi-function peripheral 1. The computer realized by the CPU 102, the ROM 104, and the RAM 106 executes arithmetic processing according to the program PRG stored in the ROM 104, thereby The functions of the digital multi-function peripheral 1 are realized by comprehensively controlling the components 1. The RAM 106 is used as a work area when the computer executes arithmetic processing.

  The image memory 108 stores an image to be processed by the digital multi-function peripheral 1 as image data.

  The digital multi-function peripheral 1 is provided with an operation panel 110 as a user interface. The operation panel 110 includes an operation unit that is an operation target and a display unit that displays information in a visually recognizable manner.

  The digital multifunction device 1 includes a scanner unit 112 and a printer unit 114.

  The scanner unit 112 reads an original with a CCD line sensor 132, which will be described later, and generates image data. The scanner unit 112 reads an original by an ADF (Automatic Document Feeder) method or an FBS (Flat Bed Scanner) method. The ADF method is a method of reading a document by feeding it one by one from a document bundle obtained by bundling a plurality of documents, and the FBS method is a method of reading a document placed on a contact glass. The ADF method includes a method of reading a moving document with a stationary reading optical system (sheet-through method) and a method of reading a stationary document with a reading optical system that moves. When the latter method is adopted, the scanner unit 112 repeats a reading procedure in which a document is stationary on the contact glass, the stationary document is read by the moving reading optical system, and the document that has been read is discharged.

  The printer unit 114 forms an image related to the image data on a recording medium such as recording paper by an electrophotographic method, and discharges the recording medium. The printer unit 114 includes four color image forming engines of Y (yellow), M (magenta), C (cyan), and K (black), and repeats the image formation on the recording medium four times to obtain a color image. Can be formed on a recording medium.

  The image color determination unit 116 performs predetermined processing on the image data. The image color determination unit 116 can be configured by hardware such as a dedicated LSI, but a computer realized by the CPU 102, the ROM 104, and the RAM 106 performs part or all of the processing performed by the image color determination unit 116 as a program PRG. It may be performed by executing.

  The compression / decompression unit 118 performs compression processing or decompression processing on the image data. As the image data compression method, the JPEG method or the like can be adopted for multi-tone image data, and the MH method, MR method, MMR method, JBIG method, or the like is adopted for two-tone image data. be able to. The compression / decompression unit 118 can also be configured by hardware such as a dedicated LSI, but a computer realized by the CPU 102, the ROM 104, and the RAM 106 executes a program PRG for part or all of the processing performed by the compression / decompression unit 118. You may be made to do by.

  The NCU 120 and the modem 122 are used for transmission / reception of facsimile image data via the public switched telephone network 91. The NCU 120 controls connection to the public switched telephone network 91. The NCU 120 has a function of transmitting a dial signal corresponding to the telephone number of the other party and a function of detecting an incoming call. The modem 122 is based on a facsimile transmission control procedure according to ITU (International Telecommunication Union) -T recommendation T.30. 17, V. 27ter, V.L. The facsimile image data is modulated / demodulated according to 29 or the like. Alternatively, the modem 122 can be connected to the V.V. The facsimile image data is modulated / demodulated in accordance with No. 34.

  The data communication unit 124 connects the digital multi-function peripheral 1 to the network 92 by, for example, Ethernet (registered trademark).

  Each component of the digital multi-function peripheral 1 described above is connected by a bus line 126 so that data can be transmitted and received between them.

  In the facsimile mode, the digital multi-function peripheral 1 reads a document using the scanner unit 112, and uses the NCU 120 and the modem 122 to send facsimile image data relating to the document to another facsimile machine via the public telephone exchange network 91. Then send. Further, the digital multifunction peripheral 1 receives facsimile image data transmitted from another facsimile machine via the public telephone exchange network 91 using the NCU 120 and the modem 122, and uses the printer unit 114 to transmit the facsimile. An image related to the image data is formed on a recording medium.

  In the copy mode, the digital multi-function peripheral 1 copies an image from the original to the recording medium by reading the original using the scanner unit 112 and forming an image related to the original on the recording medium using the printer unit 114. To do.

  In the scan mode, the digital multi-function peripheral 1 reads a document using the scanner unit 112 and accumulates image data related to the document in the image memory 108.

  In the print mode, the digital multi-function peripheral 1 receives image data transmitted from the personal computer via the network 92 using the data communication unit 124, and uses the printer unit 114 to receive an image related to the image data. Are formed on the recording medium.

<2 Configurations related to scan mode and print mode>
FIG. 2 is a block diagram illustrating a configuration related to processing of the digital multi-function peripheral 1 in the scan mode and the print mode. In FIG. 2, a mode determination unit 152 and a binarization unit 154 are processing blocks that represent functions realized when a computer realized by the CPU 102, the ROM 104, and the RAM 106 executes a program PRG. Of course, the mode determination unit 152 and the binarization unit 154 may be configured by hardware such as a dedicated LSI.

  Hereinafter, the configuration related to the processing of the digital multi-function peripheral 1 in the scan mode and the print mode will be described separately for “configuration related to image processing” and “configuration related to mode determination processing”.

<2.1 Configuration related to image processing>
An outline of a configuration related to image processing that causes the digital multi-function peripheral 1 to function as an image processing device will be described along the flow of image processing indicated by a solid line in FIG. 2. Image data generated by the CCD line sensor 132 is gamma corrected. After the gamma correction by the unit 134, the resolution conversion by the resolution conversion unit 136, and the color space conversion by the color space conversion unit 138 are sequentially performed, the data is output from the scanner unit 112. The image data output from the scanner unit 112 is accumulated in the image memory 108. In the print mode, the image data stored in the image memory 108 is binarized by the binarizing unit 154 as necessary, and then transferred to the printer unit 114. The printer unit 114 converts the image data into the image data. Such an image is formed on a recording medium. In the scan mode, the image data stored in the image memory 108 is binarized by the binarization unit 154 as necessary, and then subjected to compression processing by the compression / decompression unit 118.

  The CCD line sensor 132 repeats reading at a constant cycle while the reading optical system that guides light from the document to the CCD line sensor 132 scans the document, thereby causing image data expressed in RGB color space, That is, image data having color component data of R (red), G (green), and B (blue) is generated. The scanning speed of the reading optical system is set based on the resolution of the image data generated by the CCD line sensor 132 in the sub-scanning direction. Specifically, the higher the resolution in the sub-scanning direction, the slower the scanning speed of the reading optical system, and the lower the resolution in the sub-scanning direction, the higher the scanning speed of the reading optical system. The “scanning speed” is a relative moving speed between the original and the reading optical system.

  The gamma correction unit 134 performs gamma correction on the R, G, B color component data.

  In the print mode, the resolution conversion unit 136 converts the resolution in the main scanning direction of the image data from the resolution at the time of reading the document to the resolution at the time of transfer to the printer unit 114. In the scan mode, the resolution conversion unit 136 converts the main resolution of the image data. The resolution in the scanning direction is converted from the resolution at the time of reading the document to the resolution at the time of storing in the image memory 108.

  In the digital multi-function peripheral 1, when performing variable magnification copy, the resolution conversion unit 136 converts the resolution in the main scanning direction according to the magnification specified by the operator, and the scanning speed of the reading optical system is changed. The resolution in the sub-scanning direction is set to a resolution according to the scaling factor designated by the operator by making a difference from the case of performing the same size copy.

  The color space conversion unit 138 converts image data expressed in the RGB color space (hereinafter “RGB image data”) into image data expressed in the YCbCr color space (hereinafter “YCC image data”). The image data output from the color space conversion unit 138 has a luminance component Y and color difference components Cb and Cr.

  The binarization unit 154 acquires image data, generates a binarized image obtained by binarizing the color components of the image data, and stores the binarized image in the image memory 108. Here, “binarization” refers to conversion of multi-gradation image data into two-gradation image data. The binarization of the image data can be performed by a simple binarization method, a systematic dither method, an error diffusion method, or the like.

  On the other hand, the printer unit 114 acquires image data and forms an image related to the image data on a recording medium using a necessary image forming engine.

  The compression / decompression unit 118 acquires image data, generates compressed image data, and stores the compressed image data in the image memory 108.

  The processing modes of the digital multi-function peripheral 1 include “monochrome mode” and “color mode”, and “monochrome mode” includes “gray mode” suitable for a gray document and “monochrome mode” suitable for a monochrome document. .

  When scanning in the “color mode”, the color space conversion unit 138 converts the multi-gradation RGB image data input from the resolution conversion unit 136 into multi-gradation YCC image data, and the compression / decompression unit 118. However, the multi-gradation YCC image data is compressed by the JPEG method or the like and stored in the image memory 108.

When copying in the “color mode”, the color space conversion unit 138 converts the multi-gradation RGB image data input from the resolution conversion unit 136 into multi-gradation Lab image data (L ^* a ^* b ^* color). Image data expressed in space), the multi-tone Lab image data is further converted into multi-tone CMYK image data (image data expressed in the CMYK color space), and the binarization unit 154 Multi-tone CMYK image data is binarized into two-tone CMYK image data. The printer unit 113 acquires two-tone CMYK image data, and uses a necessary one of the four color image forming engines of “Y”, “M”, “C”, and “K” on the recording medium. To form a color image. Here, “necessary of the four color image forming engines of the image forming engines“ Y ”,“ M ”,“ C ”, and“ K ”” means image formation necessary for expressing colors included in an image. The idea is that only the engine needs to be operated. For example, if the color classification of the color included in the image is only “Y”, only the image forming engine of “Y” may be operated. If the color classification of the color included in the image is “R”, Only the “Y” and “M” image forming engines need be operated.

  When scanning in the “gray mode”, the color space conversion unit 138 converts the multi-gradation RGB image data input from the resolution conversion unit 136 into multi-gradation YCC image data, and the compression / decompression unit 118. However, the luminance component Y of the multi-gradation YCC image data is compressed by the JPEG method and stored in the image memory 108. Alternatively, the color space conversion unit 138 converts the multi-gradation RGB image data input from the resolution conversion unit 136 into multi-gradation YCbCr image data, and the binarization unit 154 performs multi-gradation YCC image data. The luminance component Y is binarized into a two-gradation luminance component Y by a systematic dither method or the like, and the compression / decompression unit 118 compresses the two-gradation luminance component Y by the JBIG method or the like and stores it in the image memory 108.

  When copying in the “gray mode”, the color space conversion unit 138 converts the multi-gradation RGB image data input from the resolution conversion unit 136 into multi-gradation YCC image data, and the binarization unit 154. However, the luminance component Y of the multi-gradation YCC image data is binarized into a two-gradation luminance component Y by a systematic dither method, an error diffusion method, or the like. The printer unit 113 acquires a two-tone luminance component Y, and forms a monochrome image on a recording medium using an image forming engine of “K”.

  When scanning in the “monochrome mode”, the color space conversion unit 138 converts the multi-gradation RGB image data input from the resolution conversion unit 136 into multi-gradation YCC image data, and the binarization unit 154. However, the luminance component Y of the multi-gradation YCC image data is binarized into a two-gradation luminance component Y by a simple binarization method or the like, and the compression / decompression unit 118 compresses the luminance component Y of the two gradations by the JBIG method or the like. And stored in the image memory 108.

  When copying in the “monochrome mode”, the color space conversion unit 138 converts the multi-gradation RGB image data input from the resolution conversion unit 136 into multi-gradation YCC image data, and the binarization unit 154. However, the luminance component Y of the multi-gradation YCC image data is binarized into a two-gradation luminance component Y by an error diffusion method, a simple binarization method, or the like. The printer unit 113 acquires a two-tone luminance component Y, and forms a monochrome image on a recording medium using an image forming engine of “K”.

  It should be noted that binarization when copying in the “gray mode” is preferably performed with more emphasis on gradation reproducibility than the “black and white mode”, and binarization when copying in the “black and white mode”. It is desirable that the reproducibility of characters is more important than the “gray mode”.

<2.2 Configuration related to mode determination processing>
The outline of the configuration for causing the digital multi-function peripheral 1 to function as an image color determination device will be described along the flow of the mode determination process indicated by the dotted line in FIG. 2. The image data generated by the CCD line sensor 132 is the image color determination unit 116. Are sequentially applied by the averaging unit 142, gamma correction by the gamma correction unit 144, and color space conversion by the color space conversion unit 146, and then input to the block determination unit 148. Then, the block determination unit 148 determines the color classification and the luminance classification to which the block belongs, the determination counting section 150 counts the number of blocks belonging to each of the color classification and the luminance classification, and the mode determination section 152 performs the document determination. Features are determined. The mode determination unit 152 further sets the processing mode of the digital multi-function peripheral 1 to a mode suitable for the characteristics of the document, and performs processing corresponding to the set mode in the binarization unit 154, the printer unit 114, and the compression / decompression unit 118. Let it run.

The averaging unit 142 calculates an average value of pixel data for each pixel set including a plurality of pixels. Since the image data input to the averaging unit 142 is expressed in the RGB color space, the pixel data is composed of R, G, and G color component data. For this reason, the averaging unit 142 calculates an average value for each of the R, G, and B color component data for each pixel set including a plurality of pixels. That is, n pixels P _i (i = 1, 2,..., N) are included in the pixel set, and R, G, B color component data of the pixels P _i are respectively R _i , G _i. , B _i , the averaging unit 142 calculates the average values R _avg , G _avg , B _avg of the R, G, B color component data according to the equation (1).

In this embodiment, the pixel set is composed of four adjacent pixels of 2 in the vertical direction (sub-scanning direction) × 2 in the horizontal direction (main scanning direction). The average values R _avg , G _avg , and B _avg of R, G, and B color component data in each pixel set constitute unit data that expresses colors in subsequent processing. The unit data is a constituent unit of coarse image data that is coarser than the image data before averaging. Such averaging is not necessarily essential, and the unit data may be composed of color component data of each pixel. However, if the unit data is constituted by the average values R _avg , G _avg , and B _avg of the color component data for each pixel set, the R, G, B reading lines in the CCD line sensor 132 have a line interval of several μm. Therefore, the influence of the false color due to the provision of the block determination unit 148 can be eliminated, and the determination in the block determination unit 148 can be performed with high accuracy.

  The false color described above often becomes a problem when performing variable-size copying. This is because if the line interval of the R, G, B reading lines of the CCD line sensor 132 corresponds to an integral multiple of the reading interval in the sub-scanning direction, the reading line preceding the reading timing in the subsequent reading line. Although it is possible to prevent false colors by delaying more, even if the “integer multiple” relationship is established when performing the same size copy, the “integer multiple” relationship is established when performing the variable size copy. This is because there is no limit.

  For example, let us consider a case where the resolution in the sub-scanning direction at the time of copying at the same magnification is 600 dpi and the line interval corresponds to four times the reading interval. In this case, when performing the same-size copy, the false timing can be prevented by delaying the read timing in the subsequent read line by four cycles from the preceding read line, but when performing the 70% reduced copy. Since the resolution in the sub-scanning direction is 420 dpi and the line interval corresponds to 2.8 times the reading interval, even if the reading timing in the subsequent reading line is delayed by three cycles from the preceding reading line, The reading position is shifted by 0.2 times the reading interval from the subsequent reading line, which causes false color.

  In addition, a mechanical shift in the formation position of the R, G, and B reading lines of the CCD line sensor 132 may cause false colors.

  In addition, the size of the pixel set should be determined according to the line interval, scaling factor, and the like, and the above-mentioned “vertical 2 × 2 horizontal 4 pixels” is merely an example. Absent.

  For example, in order to eliminate the influence of false colors when performing variable magnification copying, it is effective to increase the number of pixels in the sub-scanning direction of the pixel set as the “reading position shift” increases. Since the “positional deviation” is determined by the scaling factor, a table describing the relationship between the scaling factor and the number of pixels in the sub-scanning direction of the pixel set is prepared in advance in the ROM 104, and the specified scaling factor is referred to. It is desirable to determine the number of pixels in the sub-scanning direction of the pixel set according to the magnification.

  Note that the averaging unit 142 averages image data that has not been subjected to resolution conversion by the resolution conversion unit 136. Therefore, there is no particular problem even if the number of pixels in the main scanning direction of the pixel set is constant. Averaging in the main scanning direction is effective for false colors caused by the above-mentioned “mechanical shift”.

  However, it is not essential for the averaging unit 142 to perform averaging in both the vertical and horizontal directions. That is, the averaging unit 142 may perform averaging only in either the vertical direction or the horizontal direction.

  The gamma correction unit 144 and the color space conversion unit 146 have the same circuit configuration as the gamma correction unit 134 and the color space conversion unit 138, respectively, but the correction tables and coefficients applied to the processing are different.

  The block determination unit 148 determines the color classification to which each of the blocks obtained by dividing the image relating to the document vertically and horizontally. Here, the “block” is, for example, an area including a set of 900 pixels of 30 vertical pixels × 30 horizontal pixels. The scanner unit 112 reads an original at 600 dpi and is adjacent to 2 vertical pixels × 2 horizontal pixels. When averaging is performed with respect to the four pixels, it corresponds to an area of 5 mm long × 5 mm wide in the document. Therefore, when an original of 210 mm long × 297 mm wide is read at 600 dpi and averaged for four adjacent pixels of 2 vertical pixels × 2 horizontal pixels, the image relating to the original is 2520 × 42 × 60 horizontal. Divided into blocks. The “color classification to which each block belongs” is a total of seven color classifications including one achromatic color classification and six chromatic color classifications of R, G, B, Y, M, and C. Selected from the color category.

  Further, the block determination unit 148 determines the luminance classification to which each of the blocks belonging to the achromatic color classification belongs. The “luminance classification to which each block belongs” is selected from three luminance classifications of white, gray, and black.

  The determination counting unit 150 counts the number of blocks belonging to each of the seven color categories. Further, the determination counting unit 150 also counts the number of blocks belonging to each of the three luminance categories.

  The mode determination unit 152 uses the determination result of the block determination unit 148 to specify the color classification of the colors included in the image, and determines whether the image is a color image or a monochrome image. The “color classification of colors included in the image” also includes a total of seven colors, one achromatic color classification and six chromatic color classifications of R, G, B, Y, M, and C. Selected from the category. If the mode determination unit 152 determines that the image is a color image, the mode determination unit 152 determines that the document is a color document, and sets the processing mode of the digital multifunction peripheral 1 to the color mode.

  If the mode determination unit 152 determines that the image is a monochrome image, the mode determination unit 152 further determines the characteristics of the document using the determination result of the block determination unit 148, and the document is either a blank document, a gray document, or a monochrome document. It is determined whether it is. When the mode determination unit 152 determines that the document is a blank document, the mode setting unit 152 sets the processing mode of the digital multifunction device 1 to the blank page mode. When the mode determination unit 152 determines that the document is a gray document, the digital multifunction device 1 Is set to a mode suitable for gray originals (for example, “text / photo mode”, “photo mode”, etc.), and if it is determined that the original is a black and white original, the processing mode of the digital multifunction peripheral 1 is set. A mode suitable for a black and white document (for example, “character mode”) is set.

  If it is known from the beginning that the image is a monochrome image, the mode determination unit 152 does not need to determine whether the image is a color image or a monochrome image. For example, when making a determination on monochrome image data generated using only the G reading line of the CCD line sensor 132 or making a determination on monochrome image data obtained by extracting the luminance component Y of the YCC image data, the image is a color image and There is no need to determine whether the image is a monochrome image.

  According to such a configuration, when the original can be regarded as a blank original, the binarizing unit 154 and the compression / decompression unit 118 do not perform any particular processing.

  Further, according to such a configuration, it is possible to cause the digital multi-function peripheral 1 to perform appropriate copying or scanning according to the characteristics of the document.

<2.3 Block determination unit>
Next, the configuration of the block determination unit 148 will be described in more detail with reference to the block diagram of FIG. As illustrated in FIG. 3, the block determination unit 148 includes an affine transformation unit 162, a unit data determination unit 164, a unit data counting unit 166, a color determination unit 168, and a luminance determination unit 170.

  The affine transformation unit 162 applies affine transformation to the color difference components Cb and Cr of the unit data to obtain color parameters Cb1 and Cr1 related to the color difference. This affine transformation is the same as the affine transformation applied to the entire hue when obtaining the color plane H1 from the color plane H0 as will be described later. The unit data is adapted to the color plane H1 used by the block determination unit 148. It is intended to make it.

  The unit data determination unit 164 determines, for each pixel set included in the block, to which of the above-described seven color classifications the unit data belongs. Specifically, the unit data determination unit 164 has seven points on the color plane H1 shown in FIG. 4 that correspond to the colors represented by the unit data, that is, seven points on which the color parameters Cb1 and Cr1 of the unit data are plotted. It is determined which of the partial areas mA, mM, mB, mC, mG, mY, and mR belongs to, and the unit data belongs to the color classification corresponding to the partial area to which the point corresponding to the color represented by the unit data belongs. Color classification. Here, the partial areas mA, mM, mB, mC, mG, mY, and mR correspond to the achromatic colors, M, B, C, G, Y, and R, respectively.

Further, the unit data determination unit 164 determines whether the unit data belonging to the achromatic color classification corresponds to white, gray, or black. Specifically, the unit data determination unit 164 checks the magnitude relationship between the luminance component Y of the unit data and the threshold values Y ₁ and Y ₂ (Y ₁ > Y ₂ ) related to the luminance, and if Y ≧ Y ₁ , It is determined that the data corresponds to white. If Y ₁ > Y ≧ Y _2, it is determined that the unit data corresponds to gray, and if Y ₂ > Y, it is determined that the unit data corresponds to black. That is, “white” here is not a “overexposed” state in which the luminance reaches the upper limit value Y _max as shown in the schematic diagram of FIG. 5, but a constant luminance close to the upper limit value Y _max . The bright state in the range (Y _{1 to} Y _max ) means “black” here, not the “blackout” state where the luminance has reached the lower limit Y _min but the luminance is close to the lower limit Ymin. It means a dark state within a certain range (Y _{min to} Y ₂ ). In this way, it is possible to prevent most of the unit data from being determined to correspond to gray under the influence of slight dirt on the document or noise generated in the CCD line sensor 132.

Note that when determining the achromatic color classification to which the unit data belongs, instead of using the luminance component Y in the YCbCr color space, it may be determined using the lightness component L ^* in the L ^* a ^* b ^* color space.

  The unit data counting unit 166 counts the number of unit data belonging to each of the seven color categories. Further, the unit data counting unit 166 counts the number of unit data corresponding to white, gray, and black for the unit data belonging to the achromatic color classification.

  The color determination unit 168 determines the color classification to which each block belongs based on the counting result (number of unit data belonging to each color classification) of the unit data counting section 166. Specifically, a threshold value is set in advance for each of the seven color categories described above, and a color category in which the number of unit data to which the unit belongs exceeds the threshold value is set as a color category to which the block belongs. According to this determination method, there may be two or more color sections to which a block belongs.

  The luminance determination unit 170 determines the luminance classification to which each of the blocks belonging to the achromatic color classification belongs, based on the counting result (number of unit data corresponding to white, gray, and black) of the unit data counting section 166.

Specifically, the brightness determination unit 170, the number of unit data corresponding to gray (hereinafter "gray Units Data") number of gray threshold TG _g and white gray threshold TG _wg and unit data corresponding to black about NG (Hereinafter referred to as “the number of black unit data”) A black and white threshold value TB _wb for NB is set in advance, and the magnitude relationship between the gray unit data number NG, the gray threshold value TG _g and the white gray threshold value TG _wg, and the black unit data number NB The magnitude relationship with the black and white threshold TB _wb is examined, and the luminance classification to which the block belongs is specified according to the result. That is, when the gray unit data number NG is larger than the gray threshold value TG _g (NG> TG _g ), the luminance determination unit 170 determines that the block is classified as a gray luminance division because a certain region or more in the block is a gray portion. Judge as belonging. On the other hand, when the gray unit data number NG is smaller than the white gray threshold value TG _wg (NG <TG _wg ) and the black unit data number NB is smaller than the monochrome threshold value TB _wb (NB <TB _wb ), Since a certain area or more in the block is a bright part, it is determined that the block belongs to the white luminance division. Further, the luminance determining unit 170 determines that the block belongs to the black luminance category in the case of the residual.

  However, such determination of the luminance classification to which the block belongs is merely an example, and the luminance classification to which the block belongs is determined in consideration of the number of unit data corresponding to white (hereinafter, “number of white unit data”) NW. Alternatively, the brightness classification to which the block belongs may be determined in consideration of only one of the white unit data number NW, the gray unit data number NG, and the black unit data number NB.

As an example of the latter, for example, if the gray unit data number NG is larger than the gray threshold value TG _g (NG> TG _g ), it is determined that the block belongs to the gray luminance category, and the gray unit data number NG is the gray threshold value TG _g. If it is below the white gray threshold TG _wg (TG _g ≧ NG> TG _wg ), it is determined that the block belongs to the black luminance category, and if the gray unit data number NG is less than or equal to the white gray threshold TG _wg (TG _wg ≧ NG), it is conceivable to determine that the block belongs to the white luminance category. Of course, when such a determination is adopted, it is only necessary to determine whether or not the unit data belongs to the gray luminance classification, and therefore the configuration for the mode determination process can be simplified. Such a determination based only on the gray unit data number NG can be adopted because if there is a dark part in the block, it is considered that a gray part is always present at the boundary between the bright part and the dark part. According to this determination, if the entire image is a bright part or a dark part, it is determined that all the blocks belong to the white luminance category.

  As yet another example, the brightness classification to which the block belongs may be determined in consideration of only two of the white unit data number NW, the gray unit data number NG, and the black unit data number NB.

  For example, (1) if the gray unit data number NG is larger than the threshold TG (NG> TG) and the black unit data number NB is larger than the threshold TB (NB> TB), a gray part exists at the boundary between the bright part and the dark part Therefore, it is determined that the block belongs to the black luminance classification, and (2) the gray unit data number NG is larger than the threshold TG (NG> TG) and the black unit data number NB is equal to or less than the threshold TB. (TB ≧ NB), since there is mainly a gray portion, it is determined that the block belongs to the gray luminance classification, and (3) the gray unit data number NG is equal to or less than the threshold TG (TG ≧ NG), the black unit data If the number NB is larger than the threshold value TB (NB> TB), it is determined that the block belongs to the black luminance category mainly because there is a dark part. (4) The gray unit data number NG is equal to or less than the threshold value TG (TG ≧ NG), black If position data number NB is equal to or smaller than the threshold value TB (TB ≧ NB), primarily because it is considered that the light portion is present, it determines that the block belongs to the brightness segment white. Of course, when such a determination is adopted, it is only necessary to determine whether the unit data belongs to the gray luminance division and whether the unit data belongs to the black luminance division, so the configuration for the mode determination processing is simplified. Can be

  If the determination of the color classification and the luminance classification for each block is adopted, even if the original has a stain significantly smaller than the block size, the stain is classified as “the color division to which the block belongs” and “the luminance division to which the block belongs”. Therefore, it is possible to appropriately determine the characteristics of the document.

  In addition, if such a determination of the color classification for each block is adopted, when a large area of a certain block is an achromatic area and a remaining area of the block is a chromatic area, the block Since the chromatic color classification can be adopted as the color classification to which the image belongs, it can be reduced that the image to be determined as the color image is determined as the monochrome image.

  Further, when such determination of color classification and luminance classification for each block is employed, an area on the document to be determined can be set to a desired range by appropriately selecting a block to be used for determination.

<2.4 Color plane H1>
The color plane H1 is a two-dimensional color plane in which two coordinate axes of a Cb1 axis (horizontal axis) associated with the color parameter Cb1 and a Cr1 axis (vertical axis) associated with the color parameter Cr1 are orthogonal.

  Similar to the CbCr chromaticity diagram of the YCbCr color space, the color plane H1 has a property that the saturation shown as it approaches the origin O decreases. For this reason, in the color plane H1, the partial area mA including the origin O is a partial area corresponding to the achromatic color classification. The partial area mA is a square (more generally, a rectangle) surrounded by two saturation boundary lines D01 and D02 parallel to the Cb1 axis and two saturation boundary lines D03 and D04 parallel to the Cr1 axis. ). If such a partial area mA is set in the color plane H1, whether or not the color parameter Cb1 is included between the upper limit value -w and the lower limit value + w, and the color parameter Cr1 is lower limit value -w and the upper limit value. If it is confirmed whether or not it is included between the values + w, it can be determined whether or not the point corresponding to the color represented by the unit data belongs to the partial area mA without performing a complicated calculation. Therefore, it becomes easy to determine whether or not the image is a monochrome image in the mode determination process.

  On the outside of the partial area mA, six chromatic colored partial areas mM, mB, mC, mG, mY, and mR, which are partitioned by hue boundary lines D1 to D5 extending radially from the origin O, are set. In the color plane H1, the hue boundary line D1 is the boundary between the partial region mR and the partial region mM, the hue boundary line D2 is the boundary between the partial region mM and the partial region mB, and the hue boundary line D3 is the partial region mB and the partial region mC. , The hue boundary line D4 is the boundary between the partial area mC and the partial area mG, the hue boundary line D5 is the boundary between the partial area mG and the partial area mY, and the hue boundary line D6 is the boundary between the partial area mY and the partial area mR It has become.

  Among the hue boundary lines D1 to D6, the hue boundary lines D1 and D4 are set on the Cr1 axis, and the hue boundary lines D2, D3, D5, and D6 are respectively divided into two equal parts, that is, It is set so as to form an angle of 45 ° with the Cb1 axis and the Cr1 axis in the quadrant. If the hue boundary lines D1 to D6 are set in this way, the color parameters Cb1 and Cr1 are set to the color plane H1 based on the positive / negative of the color parameters Cb1 and Cr1 and the magnitude relationship between the absolute value of the color parameter Cr1 and the absolute value of the color parameter Cr1. It is possible to easily determine which of the six partial regions mM, mB, mC, mG, mY, and mR belongs to the points plotted in FIG. For example, if both the color parameters Cb1 and Cr1 are positive, it can be determined that the plot point is in the first quadrant. If the absolute value of the color parameter Cr1 is larger than the absolute value of the color parameter Cb1, the plot point is in the partial region mM. Can be determined to belong to.

  Such a color plane H1 can be obtained by applying affine transformation such as rotation transformation and scaling transformation to the color plane H0 corresponding to the CbCr chromaticity diagram of the YCbCr color space.

  Here, a method of obtaining the color plane H1 will be described with reference to FIGS.

  In obtaining the color plane H1, first, as shown in FIG. 6, the color plane H0 corresponding to the CbCr chromaticity diagram of the YCbCr color space, that is, the Cb axis (horizontal axis) associated with the color difference component Cb, Hue boundary lines D1 to D6 are set on a color plane H0 having an orthogonal coordinate system in which two coordinate axes orthogonal to the Cr axis (horizontal axis) associated with the color difference component Cr are orthogonal. The hue boundary lines D1 to D6 may be set based on human vision, but if set as they are based on human vision, two hue boundary lines (for example, hue boundary lines D2 and D2, which are substantially symmetric with respect to the origin O). D5) is set to be on a straight line passing through the origin O.

  Subsequently, the rotation transformation around the origin O is applied to the entire hue so that the hue boundary lines D1, D4 close to the vertical axis coincide with the vertical axis. As a result, as shown in FIG. 7, the orthogonal coordinates in which the two coordinate axes of the Cb2 axis (horizontal axis) associated with the color parameter Cb2 and the Cr2 axis (vertical axis) associated with the color parameter Cr2 are orthogonal to each other. A color plane H2 having a system is obtained.

  Subsequently, anisotropic scaling conversion (in the horizontal axis direction and the horizontal axis direction) is performed so that the hue boundary lines D2, D3, D5, D6 that do not coincide with the vertical axis form an angle of 45 ° with the horizontal axis and the vertical axis in each quadrant. (Scaling conversion in which the enlargement ratio or the reduction ratio differs in the vertical axis direction) is applied to the entire hue. As a result, as shown in FIG. 8, orthogonal coordinates in which two coordinate axes of the Cb3 axis (horizontal axis) associated with the color parameter Cb3 and the Cr3 axis (vertical axis) associated with the color parameter Cr3 are orthogonal to each other. A color plane H3 having a system is obtained.

  A color plane H1 shown in FIG. 4 is obtained by further setting saturation boundary lines D01 to D04 for the color plane H3.

When the color space conversion unit 146 converts image data expressed in the RGB color space into image data expressed in the L ^* a ^* b ^* color space, the color plane used in the block determination unit 148. H1 is a two-dimensional color plane with orthogonal coordinate system in which the two axes of the b ^* axis, which are associated with a chromaticity component a ^* and association was a ^* axis and the chromaticity component b ^* is orthogonal What is necessary is just to obtain by applying affine transformation, such as rotation transformation and scaling transformation, similarly.

More generally, the image data output from the color space conversion unit 146 includes one achromatic component (for example, the luminance component Y in the YIQ color space, the luminance component Y in the YCbCr color space, and the L ^* a ^* b ^* color space. Lightness components L, L ^* u ^* v ^* lightness component L in color space) and two chromatic components (for example, color difference components I, Q in YIQ color space, color difference components Cb, Cr, L in YCbCr color space) ^* a ^* b ^* color space used in the block determination unit 148 in the case of being composed of chromaticity components a ^* , b ^* , L ^* u ^* v ^* lightness components u ^* , v ^*, etc. H1 is a two-dimensional color having an orthogonal coordinate system in which two coordinate axes of a chromatic axis associated with the first chromatic component and a chromatic axis associated with the second chromatic component are orthogonal Affine transformation such as rotation transformation and scaling transformation is applied to the plane. What is necessary is just to be obtained by applying like.

  If the color plane H1 as described above is used in the block determination unit 148, the amount of calculation when determining the color classification to which the unit data belongs can be reduced. It does not prevent the use of the color plane. For example, as shown in FIG. 5, a color plane H0 corresponding to the CbCr chromaticity diagram in the YCbCr color space with a partial area mA including the origin O may be used.

  In the above description, the color plane H1 is divided into six chromatic partial areas mM, mB, mC, mG, mY, and mR along hue boundary lines D1 to D5 extending radially from the origin O, and unit data is The color classification to which the unit data belongs is determined by determining the positional relationship between the point corresponding to the color to be expressed and the hue boundary lines D1 to D5 (the magnitude relationship between the absolute value of the color parameter Cb1 and the absolute value of the color parameter Cr). However, the number of chromatic color partial regions can be easily increased by increasing the number of hue boundary lines. For this reason, the color plane H1 is divided into seven or more chromatic color partial areas, and a unit is formed from a total of eight or more color sections, one achromatic color section and seven or more chromatic color sections. It is easy to select the color classification to which the data belongs.

<3 Mode determination processing procedure>
FIG. 9 is a flowchart illustrating a procedure of mode determination processing in the digital multi-function peripheral 1.

  In the mode determination process, first, the mode determination unit 152 determines whether or not the document is a color document (step S101). At this time, the mode determination unit 152 acquires the number of blocks belonging to each of the color classifications from the determination counting unit 150, acquires a preset color determination reference value from the ROM 104, and blocks that belong to the chromatic color classification The size relationship between the total number of colors and the color criterion value is examined. Then, if the total number of blocks belonging to the chromatic color classification is equal to or greater than the color determination reference value, the mode determination unit 152 determines that the image related to the document is a color image, and the document is a color document. Is determined.

  When the mode determination unit 152 determines that the document is a color document (“YES” in step S101), the mode determination unit 152 sets the processing mode of the digital multifunction peripheral 1 to the color mode (step S102).

  On the other hand, if the mode determination unit 152 determines that the document is not a color document (determines that the document is a monochrome document) ("NO" in step S101), it subsequently determines whether the document is a blank document (step S101). Step S103). At this time, the mode determination unit 152 obtains the number of blocks belonging to the white luminance category from the determination counting unit 150, and when all the blocks belong to the white luminance category, the entire image related to the document Therefore, it is determined that the document is a blank document.

  When the mode determination unit 152 determines that the document is a blank document (“YES” in step S103), the mode determination unit 152 sets the processing mode of the digital multifunction peripheral 1 to a blank mode suitable for the blank document (step S104).

  When the mode determination unit 152 determines that the document is not a blank document ("NO" in step S103), the mode determination unit 152 further determines whether the document is a gray document (step S105). At this time, the mode determination unit 152 acquires the number of blocks belonging to the gray luminance category from the determination counting unit 150, acquires a preset gray reference value from the ROM 104, and determines the number of blocks belonging to the gray reference value. Compare the magnitude relationship of. Then, when the number of blocks belonging to the mode exceeds the gray reference value, the mode determination unit 152 determines that the document is a gray document because gray occupies a certain portion of the image related to the document.

  When the mode determination unit 152 determines that the document is a gray document (“YES” in step S105), the mode determination unit 152 sets the processing mode of the digital multifunction peripheral 1 to a mode suitable for the gray document (step S106). If not ("NO" in step S105), the processing mode of the digital multi-function peripheral 1 is set to a mode suitable for a monochrome document (step S107).

  According to such a mode determination process, even if the image related to the document is a monochrome image, it is possible to cause the digital multi-function peripheral 1 to perform a process suitable for the characteristics of the document. For example, in the digital multi-function peripheral 1, binarization processing is performed on image data related to a black and white document that is less required to be expressed in multiple gradations, while a gray document that is highly required to be expressed in multiple gradations. Such image data is not subjected to binarization processing, or is subjected to binarization processing that emphasizes gradation reproducibility. Alternatively, in the digital multi-function peripheral 1, the image forming engine is not operated to print image data related to a blank original that does not include substantial image information.

  In addition, according to such a determination process, when the gray reference value changes, the determination result of the mode determination unit 152 also changes, so that the gray reference value can be adjusted so that a desired process is performed. Good.

  In addition, the above-described determination criterion for document characteristics is an example in which good results can be obtained, but it does not preclude the use of other determination criteria. For example, instead of determining that the original is a blank original when all the blocks belong to the white luminance classification, the original is a blank original when the number of blocks belonging to the white luminance classification exceeds a predetermined number. You may make it determine with it. Alternatively, the number of blocks belonging to the black luminance section may be taken into consideration, and for example, the document may be determined to be a blank original even when all the blocks belong to the black luminance section.

<4 other>
In the above-described embodiment, the luminance classification to which the unit data or block belongs is selected from three luminance classification candidates, but may be selected from four or more luminance classification candidates. When the brightness category to which the unit data or block belongs is selected from four or more brightness categories, for example, one brightness category on the high brightness side is selected as the white brightness category, and one brightness category on the low brightness side is selected. Two or more luminance divisions having intermediate luminance between the black luminance division, the white luminance division, and the black luminance division can be regarded as the gray luminance division. Of course, two or more luminance segments on the high luminance side may be white luminance segments, and two or more luminance segments on the low luminance side may be black luminance segments. Note that the number of brightness classification candidates to which the unit data or block belongs is not particularly limited, but may be eight for convenience of processing by the computer.

1 is a block diagram showing an overall configuration of a digital multi-function peripheral 1 according to a preferred embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration related to processing of the digital multi-function peripheral 1 in a scan mode and a print mode. It is a block diagram which shows the structure of the block determination part 148. FIG. It is a figure which shows the color plane H1 used by the block determination part 148. FIG. It is a figure explaining the brightness | luminance range of white, gray, and black in the unit data determination part 164. FIG. It is a figure which shows the color plane H0 equivalent to the CbCr chromaticity diagram of YCbCr color space. It is a figure which shows the color plane H2 which has an orthogonal coordinate system with which Cb2 axis | shaft and Cr2 axis | shaft orthogonally crossed. It is a figure which shows the color plane H3 which has the orthogonal coordinate system with which Cb3 axis | shaft and Cr3 axis | shaft orthogonally crossed. 4 is a flowchart illustrating a procedure of mode determination processing in the digital multi-function peripheral 1.

Explanation of symbols

1 Digital MFP 102 CPU
104 ROM
106 RAM
108 Image memory 112 Scanner unit 114 Printer unit 116 Image processing unit 118 Compression / decompression unit PRG program

Claims (12)

Luminance classification determination means for determining whether each of the blocks obtained by dividing the image relating to the original document belongs to white, gray, or black luminance classification;
A determination unit that determines a processing mode of the image using a determination result of the luminance classification determination unit;
An image color determination apparatus comprising:   The image color determination apparatus according to claim 1, wherein the determination unit sets the processing mode of the image to a first mode when all the blocks belong to a white luminance category.   The said determination means makes the processing mode of the said image a 2nd mode, when the number of the blocks which belong to the brightness | luminance classification | category of a grayscale is more than a reference value. Image color determination device.   4. The method according to claim 1, wherein the determination unit sets the processing mode of the image to a third mode when the number of blocks belonging to the gray luminance division is smaller than a reference value. The image color determination apparatus described. Averaging means for averaging pixel data for each pixel set including a plurality of pixels;
Pixel data determination means for determining whether the pixel data averaged by the averaging means belongs to a brightness classification of white, gray, or black;
Further comprising
2. The luminance classification determining unit according to claim 1, wherein a determination result of the pixel data determination unit is used to determine whether each of the blocks belongs to a white, gray, or black luminance classification. Item 5. The image color determination device according to any one of Items 4 to 6. A copy means for copying an image from a manuscript to a recording medium;
Further comprising
6. The image color determination apparatus according to claim 5, wherein the number of pixels included in the pixel set is determined based on a scaling factor at the time of copying. Conversion means for converting the resolution of the image data relating to the original;
Further comprising
7. The image color determination apparatus according to claim 1, wherein a processing mode of the image is determined based on image data before resolution is converted by the conversion unit. Unit data determination means for determining whether or not unit data as a constituent unit of image data relating to the image belongs to a gray luminance classification;
A counting means for counting the number of gray unit data, which is the number of unit data belonging to the gray luminance classification;
Further comprising
The luminance classification determining unit determines that the block belongs to the gray luminance classification when the number of gray unit data exceeds the first threshold, and when the number of gray unit data is equal to or less than the first threshold and exceeds the second threshold, 8. The method according to claim 1, wherein the block is determined to belong to a black luminance section, and if the number of gray unit data is equal to or smaller than a second threshold value, the block is determined to belong to a white luminance section. Image color determination device. Unit data determination means for determining whether or not unit data as a constituent unit of the image data relating to the image belongs to a gray luminance classification and whether to belong to a black luminance classification;
A counting means for counting the number of gray unit data that is the number of unit data belonging to the gray luminance classification and the number of black unit data that is the number of unit data belonging to the black luminance classification;
Further comprising
The luminance classification determining means includes
If the number of gray unit data exceeds the first threshold and the number of black unit data exceeds the second threshold, it is determined that the block belongs to the black luminance category, and the number of gray unit data exceeds the first threshold and the number of black unit data is the first. When the threshold value is 2 or less, it is determined that the block belongs to the gray luminance category. When the gray unit data number is equal to or less than the first threshold value and the black unit data number exceeds the second threshold value, the block is determined to belong to the black luminance category. 8. The method according to claim 1, wherein when the number of gray unit data is less than or equal to the first threshold and the number of black unit data is less than or equal to the second threshold, it is determined that the block belongs to a white luminance category. 2. An image color determination apparatus according to 1. Color classification determination means for determining the color classification to which each of the blocks belongs;
Achromatic color determining means for determining whether or not the image is an achromatic image using the determination result of the color classification determining means;
Further comprising
9. The image color determination according to claim 1, wherein when the achromatic color determination unit determines that the image is an achromatic image, a processing mode of the image is determined. apparatus. A luminance classification determination step for determining whether each of the blocks obtained by dividing the image relating to the document belongs to a luminance classification of white, gray, or black;
A determination step of determining a processing mode of the image using a determination result of the luminance classification determination step;
An image color determination method comprising: A luminance classification determination procedure for determining whether each of the blocks obtained by dividing the image related to the original document belongs to a white, gray, or black luminance classification;
A determination procedure for determining a processing mode of the image using a determination result of the luminance classification determination procedure;
An image color determination program that causes a computer to execute the above.

Images