JP4847092B2 - Image processing apparatus and toner saving method - Google Patents

Description

  The present invention relates to an image processing apparatus and a toner saving method, and more particularly to an image processing apparatus and a toner saving method for automatically discriminating a document using automatic color selection (ACS).

  Conventionally, a technique for switching to a monochromatic image forming operation when a monochromatic color (monochromatic) is discriminated is known (Patent Document 1). However, with such a technique, it is impossible to identify mono-colors other than substantially monochrome.

  Conventionally, color pixel blocks and automatic color selection (hereinafter referred to as ACS) have been used as functions for automatically determining and improving productivity when copying a mixed original of a color original and a monochrome original on a full-color copying machine or the like. There are known techniques for discriminating pixels that are used at a plurality of white levels of W pixels for color and W pixels for color pixels (Patent Documents 2 and 3). Normally, the image forming process of full-color copying is performed in order of the copying process for each of the four basic colors of cyan (C), magenta (M), yellow (Y), and black (K) (or three of CMY). Execute and transfer these colors on a single recording sheet. That is, a copy process for each of the four colors is necessary. On the other hand, when executing the copy process in the monochrome mode, one image is copied in one copy process. Therefore, in this type of copying machine, the time required for the copying operation varies greatly between the full color mode and the monochrome mode, so the operator needs to pay attention to switching between the full color mode and the monochrome mode, depending on the type of document. Therefore, an operation for switching the copy mode appropriately must be performed (Patent Document 4). In order to eliminate the troublesome mode switching, ACS is used, and a technique for automatically identifying whether a document is color or monochrome and automatically switching the operation mode of the copier according to the identification result is disclosed (Patent Literature). 5, 6) Known.

  In recent years, copying machines equipped with a mode for performing two-color copying or mono-color copying on a full-color copying machine are increasing. The two-color copy is a mode in which a specific color of the original and another color other than the original color are reproduced with different colors. For example, a two-color copy mode that reproduces a red portion of an original as red and reproduces the others in black is widely known. In this case, the number of image formation is MYK 3C color and the number of image formation is 3, which is usually called two-color copy. The mono color copy is a mode for reproducing an original with only a specific color, and a plurality of color plates are required depending on the color.

  Copying in full color is expensive, but copying in these modes is considerably cheaper than full color, and in some cases it is possible to obtain a colored copy at the same charge as monochrome, which is a very cost advantage Is big. For example, for a manuscript written in red for monochrome, it is not necessary to make a full-color copy at a high cost, and a two-color copy of red and black is sufficient.

  Also, there is a difference in productivity between creating a full-color CMYK four-color original for two colors of red and black and copying in a two-color mode (three versions of MY + K). Considering copying 100 sheets, the calculation takes about ¾ of the time required for full color. For example, assuming that a full-color 10 CPM machine is used as a copying machine, it takes 10 minutes for full-color operation. Color copying will take 7 and a half minutes. Other than this, meaningless image formation with no output data is concerned that in a complicated electrophotographic process, the deterioration of components, including the influence on the engine, may be brought about at an early stage.

  Therefore, an image forming apparatus using ACS for determining RGBCMYK multicolors has been proposed (Patent Document 7). In addition to color / monochrome determination, it is possible to determine each color and perform a more detailed operation that forms an image with a small number of color plates.

By the way, from the viewpoint of cost, attention should be paid to the toner as a supply item. For this, a method has been proposed in which a toner save mode that can be selected by a user is provided to suppress consumption of toner to be used. Although it becomes thinner overall in terms of image quality, it can reduce toner consumption and extend the life of the supply.
Japanese Utility Model Publication No. 04-037953 JP 2001-103301 A JP 2001-101390 A JP 63-107274 A JP-A-10-155076 JP-A-8-265583 JP 2004-155015 A

  However, there are many cases where there is no problem in image quality even if the toner is saved if it is a monochrome document or a document that is marked with a marker pen or the like, but it is difficult in terms of finishing with a document that is copied in full color. For this reason, there is a problem that the toner save mode cannot be uniformly applied to a document in which full color and monochrome are mixed.

  The present invention has been made in view of the above problems, and identifies a color existing in a document according to the results of a plurality of color determination means, and performs toner save processing suitable for the document based on the specified result. The purpose is to do.

In order to solve the above problems, the present invention provides a plurality of image forming units each having a different image forming color, and a color for determining an input color that is all kinds of colors used in input image data. Pixel determining means, image forming color selecting means for selecting the image forming color necessary for expressing all colors determined by the color pixel determining means, and the input color determined by the color pixel determining means And a toner saving means for determining a consumption amount of toner of the image forming color according to the required image forming color, and the toner saving means has the number of input colors of 1 When the input color is black, the consumption amount of black toner is determined without toner saving, and when the number of the input colors is 1 and the input color is not black, the contrast Lookup table that emphasizes The toner consumption means determines the consumption amount of toner of the required image forming color, and the toner saving means, when the number of the input colors is 2 and one of the input colors is black, Using a look-up table that emphasizes gradation for black and using a look-up table that emphasizes contrast for the other input color, the toner consumption of the required image forming color is determined, and the required image When the image colors are all of the image forming colors possessed by each of the plurality of image forming units, a necessary consumption amount of toner of the image forming colors is determined using a look-up table that emphasizes gradation. The image forming apparatus is characterized by the above.

The present invention also relates to a toner saving method by an image forming apparatus having a plurality of image forming means each having a different image forming color, and an input color which is all kinds of colors used for input image data. A color pixel determination step for determining the image color, an image formation color selection step for selecting the image formation color necessary for expressing all the colors determined in the color pixel determination step, and the color pixel determination step. the determined number of the input color, and, in response to the image forming colors required, and toner save step of determining the amount of toner consumption of the image forming colors, only it contains, in the toner saving step, the input When the number of colors is 1 and the input color is black, the consumption amount of black toner is determined without saving toner, the number of input colors is 1, and the input color Emphasis on contrast when is not black A required consumption amount of the toner of the image forming color is determined, and the toner saving means is configured such that the number of the input colors is 2, and one of the input colors is black. In this case, a required consumption amount of the image forming color toner is determined using a lookup table that emphasizes gradation for black and a lookup table that emphasizes contrast for the other input color. When the required image forming colors are all of the image forming colors possessed by each of the plurality of image forming units, a toner having the required image forming color is obtained using a look-up table that emphasizes gradation. The toner saving method is characterized in that the consumption amount of the toner is determined .

  According to the present invention, it is possible to execute a toner save process suitable for a document while maintaining a balance between cost reduction by supply and maintenance of image quality.

  Hereinafter, an image processing apparatus and a toner saving method according to an embodiment of the present invention will be described in detail with reference to the drawings. The embodiments described below are preferred embodiments of the present invention, and therefore technically preferable various kinds of limitations are given. However, the scope of the present invention is not limited to the following description. As long as there is no description which limits, it is not restricted to these aspects.

  FIG. 1 is a block diagram showing the configuration of a full-color copying machine according to an embodiment of the present invention. The image forming apparatus according to the present embodiment employs a CMYK accumulation method. The flow of image data during copying will be described with reference to FIG. In addition, the numerical value etc. which are used by the following description are only illustrations on description, and in this invention, it is not limited to these numerical values at all.

  When reading an original, the original set in the reading unit 1 is read and sent to the scanner correction unit 2 as 600 dpi 8-bit image data for each color separated into RGB. Although the scanner correction unit 2 sets the image data read by the scanner to 8 bits for each color of 600 dpi, the present invention is not limited to this. As shown in FIG. 2, the scanner correction unit 2 performs a scanner γ process 201, a filter process 202, a color correction process 203, and a scaling process 204. An edge of a 600 dpi 8-bit RGB color signal is enhanced by filter processing, a picture portion is smoothed, and converted to an 8-bit CMYK (color) signal of 600 dpi by color correction processing. When the copy mode is the monochrome mode, only K data is useful data.

  In parallel with this, ACS determination is also performed. For this purpose, the scanner image data before various image processing is used to determine which color is present in the image data. Details of this determination will be described later.

  The 600 dpi CMYK image data for each color after scaling is converted into 2-bit image data for each color by a fixed-length irreversible compressor (fixed-length multi-value compressor) 3. The output of the fixed-length multi-value compressor 3 is connected to the general-purpose bus I / F, and 600 dpi 2-bit CMYK image data after irreversible compression is sent to the printer controller unit 5 through the general-purpose bus I / F. When the copy mode is the monochrome mode, only K data is useful as described above. Therefore, CMY data may be discarded and only K may be transferred. In that case, the data size at the time of accumulation can be reduced to ¼. The printer controller has an independent memory (for example, a semiconductor memory) 6 (6M to 6Y) for each color, and stores sent data.

  The printer controller 5 also holds attribute data containing attribute information of the accumulated image data. For example, information such as image resolution, character / photo, image quality mode such as color / monochrome, paper size, number of prints, and the like can be given.

  The stored image data and attribute data are written to the hard disk HDD 7 which is a large capacity storage device as needed. This is because it is possible to save the trouble of reading the original again even if the paper is jammed at the time of printout and the output does not end normally, and electronic sorting for rearranging a plurality of original image data is performed. In the present exemplary embodiment, the image forming apparatus may be added with a function of accumulating read originals and re-outputting them when necessary.

  In this embodiment, lossy compression is applied to CMYK image data. However, if the general-purpose bus I / F has a sufficiently wide bandwidth and the capacity of the HDD to be stored is large, the data is handled in an uncompressed state. Also good. In this way, image deterioration due to irreversible compression can be prevented. In addition, a reversible compression method may be used, but in this case, the code length after block compression is not constant, so it becomes difficult to rotate the image for each block, and in many cases, an external memory for rotation is provided. It may be necessary.

  In the case of output, 600 dpi 2-bit CMYK compressed image data in the HDD 7 is temporarily developed in a semiconductor memory, and then sent to a plotter engine unit through a general-purpose bus. The data is converted again into 8-bit CMYK image data by a fixed length multi-value expander (fixed length uncompressed expander) 8 of the engine unit. This data is sent to the printer correction unit 9 as shown in FIG. 3, and the toner saving unit 901 suppresses the CMYK output value so that the amount of toner at the time of output is reduced as required by an instruction from the controller 5. The printer correction unit performs printer γ correction 902 for each color of CMYK, and then performs halftone processing in accordance with the writing unit (GAVD) 10 and the image forming unit 11 and outputs the result onto transfer paper.

  The toner save unit 901 can be implemented in several forms. In this embodiment, a LUT (Look Up Table) prepared for each color of CMYK is used. In addition, it is also possible to employ other than LUT.

  FIG. 4 is a block diagram showing the configuration of the full-color copying machine according to the embodiment of the present invention. The image forming apparatus according to the present embodiment employs a CMYK accumulation method. The flow of image data during scanner distribution will be described with reference to FIG. Compared with the embodiment shown in FIG. 1, the flow of image data until it is stored in the HDD is the same, and thus the description until it is stored in the HDD 7 is omitted.

  The 600 dpi 2-bit CMYK compressed image data in the HDD is temporarily expanded in the semiconductor memory 6 in the same storage format, and the CMYK data compressed by the compression / decompression block 12 is expanded. The compression / decompression block 12 includes a plurality of algorithm decompressors, and the printer controller 5 reads information about the storage format recorded in the HDD 7, instructs the algorithm to be used, and decompresses data. Thus, 600 dpi 2-bit CMYK compressed image data is decoded into 600 dpi 8-bit CMYK image data. If the corresponding algorithm does not exist, the HDD 7 returns an error to the printer controller 5. In this case, the backup data cannot be written back.

  If the compression / decompression block is programmable by a DSP (Digital Signal Processor) or the like, the degree of freedom is further expanded. You can embed the code in the firmware of the device and use it when you use it, or you can download the code from the network if necessary.

  The expanded 600 dpi 8-bit CMYK image data is output to the image format conversion unit 13 for various processing. Data is converted from the storage format 600 dpi 8-bit CMYK in the HDD 7 to the image format 200 dpi 8-bit RGB used in distribution.

  FIG. 5 is a block diagram showing a configuration example of the image format conversion unit 13 according to the embodiment of the present invention. A color conversion circuit 1301 that performs color space conversion, a resolution conversion circuit 1302 that performs image resolution conversion, a filter processing circuit 1303 that performs filter processing, a γ processing circuit 1304 that performs γ processing, and a halftone that performs halftone processing The processing circuit 1305 is configured.

  The expanded 600 dpi 8-bit CMYK image data is converted by the color conversion circuit 1301 into 600 dpi 8-bit RGB image data which is a color space in scanner distribution. The converted 600 dpi RGB image data is subjected to resolution conversion into 200 dpi 8-bit RGB image data, which is the resolution set by scanner distribution in the resolution conversion circuit 1302. Note that the resolution and color space are not particular about the example shown here (generally, it is desired that the resolution is low and the file size is small in scanner distribution), and any resolution, sRGB, YUV, or gray scale is desired. The color space may be used.

  Subsequent filter processing, γ processing, and halftone processing are performed according to user settings. In this case, it passes through without performing any processing. In this way, the accumulated 600 dpi 8-bit CMYK data is converted into 200 dpi 8-bit RGB data for scanner distribution.

  The image data converted into 200 dpi 8-bit RGB inside the main body is compressed again according to the output format in the compression / decompression block 12, and once expanded in the semiconductor memory 6, JPEG (Joint Photographic Image Experts Group) , A general-purpose image format such as TIFF (Tagged Image File Format), BMP (Bit MaP) format, etc., and distributed to an external PC through a NIC (Network Interface Controller).

  FIG. 6 is a diagram showing the configuration of a full-color copying machine that employs the CMYK storage system according to the embodiment of the present invention. It is also a block diagram explaining the flow of image data at the time of FAX distribution. Compared with the embodiment shown in FIGS. 1 and 4, the flow of image data until it is stored in the HDD is the same, and thus the description until it is stored in the HDD 7 is omitted.

The 600 dpi 2-bit CMYK compressed image data in the HDD is temporarily expanded and stored in the semiconductor memory 6 in the storage format as it is, and the CMYK data compressed by the compression / decompression block 12 is expanded. The compression / decompression block 12 includes a plurality of algorithm decompressors, and the printer controller 5 reads the storage format information recorded in the HDD 7 and instructs the algorithm to be used to perform data decompression.
Thus, 600 dpi 2-bit CMYK compressed image data is decoded into 600 dpi 8-bit CMYK image data. If the corresponding algorithm does not exist, it returns an error to the printer controller. In this case, the backup data cannot be written back.

  If the compression / decompression block 12 is programmable by a DSP or the like as described above, the degree of freedom increases, and the code can be embedded in the firmware of the device or the corresponding code can be downloaded from the network.

  The expanded 600 dpi 8-bit CMYK image data is output to the image format conversion unit 13 for various processing. The data is converted from the storage format 600 dpi 8-bit CMYK in the HDD 7 to the image format 200 dpi 1-bit monochrome binary used in, for example, FAX distribution.

  The operation of the image format conversion unit will be described again with reference to FIG. The expanded 600 dpi 8-bit CMYK image data is converted by the color conversion circuit 1301 into 600 dpi 8-bit grayscale image data that is actually a color space in FAX distribution. The converted 600 dpi grayscale image data is subjected to resolution conversion into 200 dpi 8-bit grayscale image data, which is the resolution set by the scanner distribution by the resolution conversion circuit 1302. Note that the resolution and color space are not particularly limited to the example shown here. For example, in FAX distribution, the resolution is lowered, the file size is reduced, or even in a color space such as an arbitrary resolution, sRGB, YUV, and gray scale. Can be adopted.

  Subsequent filter processing, γ processing, and halftone processing are performed suitable for FAX distribution. That is, in order to improve the legibility of characters, a filter that emphasizes edges is applied, the γ characteristics are adjusted, and error diffusion processing is performed by halftone processing. In this way, the accumulated 600 dpi 8-bit CMYK data is converted into 200 dpi 1-bit grayscale data for FAX distribution.

  The image data converted to the 200 dpi 1-bit gray scale is again compressed by the compression / decompression block 12 according to the output format (MH (Modified Hoffman) / MR (Modified Read) / MMR (Modified Modified Read), etc. in FAX)). After being developed in the semiconductor memory once, it is adjusted to a general-purpose image format to the TIFF format and distributed to the public line through the FAX controller.

  Next, the ACS determination unit shown in FIG. 2 will be described. FIG. 7 is a diagram illustrating a configuration example of the ACS determination unit 205 according to the embodiment of the present invention, and determines a color existing in a document. The color to be determined is RGBCMY, but is not limited to this. The color determination unit is a block for detecting RGBCMY. As shown in the figure, the color determination unit determines a color pixel for determining RGBCMY by determining the color pixel block of the input image data and the line memory for storing 5 lines each of the output CMYW of the hue division unit 2051 and the hue division unit. And a determination unit 2052.

  The hue division unit 2051 separates input RGB image data into RGBCMYK + ACS W signals by hue division, and extracts white pixels for color pixel determination. As an example of hue division, each color boundary is obtained, and the difference between the maximum value and the minimum value of RGB is defined as an RGB difference, and is as follows. Here, in the RGB data, it is assumed that black increases as the number increases.

1. RY hue boundary (ry) R-2 * G + B> 0? 1: 0
2. Y-G hue boundary (yg) 11 * R-8 * G-3 * B> 0? 1: 0
3. G-C hue boundary (gc) R-5 * G + 4 * B <0? 1: 0
4. CB hue boundary (cb) 8 * R-14 * G + 6 * B <0? 1: 0
5. BM hue boundary (bm) 9 * R-2 * G-7 * B <0? 1: 0
6. MR hue boundary (mr) R + 5 * G-6 * B <0? 1: 0
7. ACS W pixel determination
If (R <thw) & (G <thw) & (B <thw), y = m = c = 0.
8. Y pixel determination
If (ry == 1) & (yg == 0) & (RGB difference> thy)
Let y = 1 and m = c = 0.
9. G pixel determination
If (yg == 1) & (gc == 0) & (RGB difference> thg)
Let c = y = 1, m = 0.
10. C pixel determination
If (gc == 1) & (cb == 0) & (RGB difference> thc),
Let c = 1 and m = y = 0.
11. B pixel determination
If (cb == 1) & (bm == 0) & (RGB difference> thb),
Let m = c = 1 and y = 0.
12. M pixel determination
If (bm == 1) & (mr == 0) & (RGB difference> thm),
Let m = 1 and y = c = 0.
13. R pixel determination
If (mr == 1) & (ry == 0) & (RGB difference> thr),
Let y = m = 1 and c = 0.
14. K pixel determination When not corresponding to 7-13 above, y = m = c = 1.

  Here, the priority of the above 7-14 gives priority to the smaller number. thwa, thy, thm, thc, thr, thg, and thb are threshold values determined before the color determination operation. The RGB difference is a difference between the maximum value and the minimum value between RGB image data in one pixel.

  As an output signal, cmy is combined and output in 3 bits. That is, 3 bits represent 8 colors of CMYRGBKW. Here, the threshold value is changed for each hue because the range of chromatic colors is different for each hue region, and the threshold value needs to be determined according to the hue region. Note that the configuration of the hue division unit 2051 is an example for explanation, and the present invention is not limited to this, and other methods may be used.

  The output cmy of the hue division unit 2051 is stored in five lines in the line memory, and is input to the color pixel determination unit 2052. FIG. 8 shows an example of the configuration of the color pixel determination unit 2052 shown in FIG. 7. The count unit 20510, the color pixel determination unit 20511, the blocking unit 20512, the density unit 20513, and the RGBCMY total count unit 20514 Consists of

  The counting unit 20510 receives 5 lines of cmy data from the line memory and counts the number of pixels (c, m, y) in a 5 × 5 block (the counted numbers are nc, nm, ny, respectively). ) And sent to the next color pixel determination unit 20511. The color pixel determination unit 20511 determines the color of the target pixel under the following conditions.

1. (min (nc, nm, ny) <tha_w) W judgment 2. (nc> tha_c1) & (nc-max (nm, ny)> th_c2) C judgment 3. (nm> tha_m1) & (nm-max (ny, nc)> th_m2) M judgment 4. (ny> tha_y1) & (ny-max (nc, nm)> th_y2) Y judgment 5. (nm> tha_r1) &(ny> tha_r1) & (min (nm , ny)-nc> th_r2) R judgment 6. (ny> tha_g1) &(nc> tha_g1) & (min (ny, nc)-nm> th_g2) G judgment 7. (nc> tha_b1) &(nm> tha_b1 ) & (min (nc, nm) -ny> th_b2) B judgment 8. When not corresponding to 1-7 above, K judgment

  Here, the priority of 1-8 is given priority to the smaller number. Note that tha_w, tha_c1, tha_c2, tha_m1, tha_m2, tha_y1, tha_y2, tha_r1, tha_r2, tha_g1, tha_g2, tha_b1, and tha_b2 are preset threshold values before color determination.

  As a result, when it is determined that the color is one of RGBCMYK, only the determined color is High and the others are Low, and are sent to the block forming unit 20512 in the subsequent stage. Further, when it is determined as W, it does not correspond to any color and is all sent to the blocking unit 20512 as Low.

  The block forming unit 20512 blocks each determination output of RGBCMYK from the color pixel determining unit 20511. Here, blocking means outputting as a color pixel block when there are one or more color pixels in a 4 × 4 matrix. Therefore, the processing after the blocking unit 20512 is output in block units with 4 × 4 as one block.

  The densification unit 20513 determines that the active block is active if there are three or more active conditions in the 3 × 3 block and the target block is active in order to remove an isolated block from the output of the blocking unit 20512. The result is output to each RGBCMYK continuous counting unit 20514.

  Each RGBCMYK continuous counting unit 20514 checks the continuity of the color pixel block for each color, and determines whether the document includes each color of RGBCMYK. This result is output to a CPU (not shown).

  The operation of counting the continuity of the color pixel block of the continuous count unit will be described with reference to the flowchart of FIG. FIG. 9 is a flowchart for explaining the operation of counting the continuity of the color pixel blocks in the continuous counting unit. MS indicates an array indicating state variables of the current line, SS indicates an array of state variables one line before, I indicates a pixel block position of main scanning, Thacs indicates a threshold for determining continuity, MS [I] · SS [I] indicates a continuous count value. Although there are seven types of circuits, RGBCMYK, all the operations are the same, and the description thereof is omitted.

  First, it is determined whether or not the pixel block of interest is a color pixel block (step S100). If the pixel block of interest is not a color pixel block (step S100 / No), MS [I] = 0 is set ( Step S100 → Step S112), and then the process proceeds to Step S105. On the other hand, when the pixel block of interest is a color pixel block (step S100 / Yes), the process proceeds to step S101. In step S101, it is determined whether MS [I] = Thacs (step S101). When the result of this determination is true (step S101 / Yes), it is determined as a color original (step S113).

  If MS [I] = Thacs is not satisfied (step S101 / No), it is determined whether MS [I] ≦ SS [I + 1] (upper right block) (step S102). If it is determined that I] ≦ SS [I + 1] (step S102 / Yes), the process proceeds to step S107. On the other hand, if it is determined in step S102 that MS [I] ≦ SS [I + 1] is not satisfied (step S102 / No), the process proceeds to step S103.

  In step S107, it is determined whether SS [I] (upper block) = 0. When the determination result is not SS [I] = 0 (step S107 / No), MS [I] = SS [I + 1] is set (step S108). That is, the process proceeds to step S103 with the continuous count value of the pixel block of interest as the continuous count value of the upper right pixel block. On the other hand, if SS [I] = 0 (step S107 / Yes), it is determined in step S109 whether SS [I-1] (upper left block) = 0, and SS [I-1] = If it is not 0 (No in step S109), the process proceeds to step S108 in the same manner.

  Further, if SS [I-1] = 0 in step S109, it is determined whether MS [I-1] (left block) = 0 (step S110). If MS [I-1] = 0 as a result of this determination (step S110 / Yes), MS [I] = SS [I + 1] +1 is set (step S111). That is, the continuous count value of the pixel block of interest is incremented by 1 from the continuous count value of the upper right pixel block, and the process proceeds to step S103. On the other hand, if MS [I-1] = 0 is not 0 in step S110 (step S110 / No), the process proceeds to step S108.

  In step S103, MS [I-1] (left block) = MAX (MS [I-1], S [I-1], S [I]), and the left, upper left, and upper pixels of the pixel block of interest. The maximum continuous count value in the block is set as the continuous count value in the pixel block on the left of the target pixel block. Subsequently, it is determined whether or not MS [I] ≦ MS [I-1] (step S104). That is, it is determined whether or not the continuous count value of the pixel block of interest is equal to or less than the continuous count value of the left pixel block. As a result of this determination, if it is determined that MS [I] ≦ MS [I-1] is not satisfied (step S104 / No), the process proceeds to step S105. On the other hand, when it is determined that MS [I] ≦ MS [I-1] (Step S104 / Yes), after setting MS [I] = MS [I-1] +1 (Step S106), The process proceeds to step S105. In step S105, I = I + 1 is set, and the continuous count value in the next pixel block is detected.

  In the above flow, when the pixel block of interest is a color pixel block, if the continuous count values of the left, upper and upper left pixel blocks are all 0, the continuous count value of the upper right pixel block is incremented by 1, and When the pixel block of interest is a color pixel block, if the continuous count value of the left, upper, upper left pixel block is any other than 0, the continuous count value of the upper right pixel block is held as it is. Then, the maximum continuous count value of the adjacent pixel block (peripheral left, upper, upper left, and upper right) is set as the continuous count value of the pixel block of interest (current pixel block). However, if the target pixel block is not a color pixel block, the continuous count value is cleared to zero. That is, the continuous count value is approximately the sum of the vertical and horizontal line segments. When the continuous count value reaches a certain threshold value (Thacs), it is determined that the document is a specific color document. The reason why the continuous count value of the upper right pixel block is treated differently from others is to prevent double counting.

  As described above, in the present embodiment, each color continuous count unit refers to the continuous count value of the color pixel block in the pixel block one line before (the pixel block on the upper left, upper, and upper right with respect to the target pixel block). Then, the continuous count value of the color pixel block in the target pixel block is calculated, and when the calculated continuous count value of the color pixel block in the target pixel block is equal to or greater than the threshold value, the document is determined to be a document using a specific color. Therefore, it is possible to accurately determine whether or not the document is a specific color. In addition, it is possible to accurately determine whether the document is of a specific color even if it is erroneously determined in a small area.

  Furthermore, in the conventional ACS, only monochrome or color can be determined, but in order to determine whether the original is a color document independently of RGBCMYK, how many colors are used? Judgment is possible for the question.

  In this embodiment, the configuration example for the RGB data is shown. However, the present invention is not limited to the RGB data. For example, the hue may be determined for a luminance color difference system (Lab color space).

  Each of the RGBCMYK color determination results determined by the ACS determination unit indicates whether the toner save is ON / OFF, the toner save method, and the color plate to be applied depending on the color. An example is shown below.

  When the ACS is in the toner save mode and the ACS determination result is full color using all CMYK image forming colors, a conversion table that gently compresses shadows as shown in FIG. 10A is used. . As a result, toner can be saved while suppressing a decrease in gradation in full color output that emphasizes image quality such as gradation.

  In the ACS and toner save mode, when the ACS determination result is RGBCMY, that is, single color, a conversion table as shown in FIG. 10B is used. Although the conversion table in FIG. 10B saturates the shadow side and collapses the gradation, the toner can be saved while suppressing a decrease in contrast of a character document or the like.

  In the ACS and toner save mode, when the ACS determination result is only K, that is, monochrome, the information amount of the original is emphasized, and the toner consumption is not so much in a single version, so toner save is not performed. This can be dealt with by setting the toner save portion to “through” or setting a linear conversion table.

  In the ACS and toner save mode, when the ACS determination result is K, that is, two-color color including black in addition to any one of RGBCMY, the K plate is made through (passing) with emphasis on the amount of information and is attached. For any of the RGBCMY color plates, the toner saving process emphasizing contrast as shown in FIG. 10B is performed. As a result, the toner can be saved while maintaining the characteristics of the two-color color only in the color plate while maintaining the information such as black characters.

  As described above, in the present embodiment, it is possible to automatically apply an appropriate toner save process according to the determination result by ACS. The presence / absence of the toner saving process based on each determination result and the processing method to be applied are not limited to the above range, and can be arbitrarily applied according to the user's wishes.

  For example, there is a case where toner saving is performed when it is positively determined that the original is prepared as a monochrome original from the idea that there are many monochrome. In that case, it is preferable to perform toner save by using a conversion table as shown in FIG.

  As another embodiment according to the present invention, the user can set which process can be applied to which case. Furthermore, the user can set a favorite conversion table.

  As described above, the embodiment of the present invention has been described using the configuration example of the full-color multifunction peripheral that employs the storage method in CMYK. In the following FIGS. 11 to 15, it is explained that the RGB storage method is used, and this method can be similarly configured. FIGS. 11, 14 and 15 show an example of the configuration of a full-color multi-function peripheral that employs the RGB storage method. In the full-color multi-function peripheral in the case of storing in RGB instead of the image storage in CMYK described above. FIG. 5 is a block diagram illustrating the flow of image data during copying, scanner distribution, and FAX distribution.

  The basic operation is the same as that of the configuration example adopting the CMYK accumulation method. Others are in principle the same as the embodiment shown in FIGS. 1, 4 and 6, respectively. The difference is that the color correction circuit in the scanner correction circuit of FIG. 2 has changed to a printer correction circuit due to the change from CMYK storage to RGB storage (see FIGS. 12 and 13). The other operations are the same as those in the embodiment shown in FIGS.

  As described above, according to the embodiment, it is possible to switch whether to perform the toner save process based on the result of specifying the color existing in the document according to the result of the plurality of color determination means.

  Further, according to the above embodiment, the toner saving process can be switched based on the result of specifying the color existing in the document according to the result of the plurality of color determination means.

  Further, according to the above-described embodiment, it is possible to perform the toner saving process only for a specific color plate based on the result of specifying the color existing in the document according to the result of the plurality of color determination means.

  As mentioned above, the invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and various modifications can be made without departing from the scope of the invention. Needless to say.

2 is a schematic block diagram illustrating a configuration of a full-color digital multi-function peripheral that performs CMYK accumulation according to an embodiment of the present invention, and a diagram illustrating a flow of image data during copying. FIG. It is a block diagram of a scanner correction unit according to an embodiment of the present invention. It is a block diagram of a printer correction unit according to an embodiment of the present invention. FIG. 3 is a schematic block diagram illustrating a configuration of a full-color digital multi-function peripheral that performs CMYK accumulation according to an embodiment of the present invention and a flow of image data at the time of scanner distribution. It is a block diagram of the image format conversion part which concerns on embodiment of this invention. FIG. 2 is a schematic block diagram illustrating a configuration of a full-color digital multi-function peripheral that performs CMYK accumulation according to an embodiment of the present invention, and a diagram illustrating a flow of image data during FAX distribution. It is a schematic block diagram which shows the structural example of the ACS determination part which concerns on embodiment of this invention. It is a block diagram which shows the internal structural example of the color pixel determination part which concerns on embodiment of this invention. It is a flowchart which shows the flow of the process which counts the continuity of the color pixel block which concerns on embodiment of this invention. FIG. 6 is a configuration block diagram of a conversion table when performing toner save according to the embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a schematic block showing a configuration of a full-color digital multi-function peripheral that performs RGB accumulation according to an embodiment of the present invention and a flow of image data during copying. It is a block diagram of a scanner correction unit according to an embodiment of the present invention. It is a block diagram of a printer correction unit according to an embodiment of the present invention. FIG. 2 is a schematic block diagram illustrating a configuration of a full-color digital multi-function peripheral that performs RGB accumulation according to an embodiment of the present invention and a flow of image data at the time of scanner distribution. FIG. 2 is a schematic block diagram illustrating a configuration of a full-color digital multi-function peripheral that performs RGB accumulation according to an embodiment of the present invention and a flow of image data during FAX distribution.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reading unit 2 Scanner correction | amendment part 3 Fixed length multi-value compressor 5 Printer controller 6 Memory | storage means (semiconductor memory)
7 HDD
8 Fixed length multi-value expander 9 Printer correction unit 10 GAVD
11 Image creation unit 12 Compression / decompression block 13 Image format conversion unit

Claims (2)

A plurality of image forming means each having a different image forming color;
Color pixel determination means for determining input colors that are all kinds of colors used in input image data;
Image forming color selecting means for selecting the image forming color necessary for expressing all the colors determined by the color pixel determining means;
Toner save means for determining a consumption amount of toner of the image forming color according to the number of the input colors determined by the color pixel determining means and the required image forming color ;
The toner saving means includes
When the number of input colors is 1 and the input color is black, the consumption amount of black toner is determined without toner saving;
When the number of the input colors is 1 and the input color is not black, a consumption amount of the toner of the image forming color that is necessary is determined using a lookup table that emphasizes contrast,
When the number of the input colors is 2 and one of the input colors is black, the toner saving unit uses a look-up table in which gradation is emphasized for black, and the other input Using a look-up table that emphasizes contrast for color, determine the amount of toner consumption of the image color required,
When the required image forming colors are all of the image forming colors possessed by the plurality of image forming units, a look-up table that emphasizes gradation is used to determine the toner of the required image forming colors. An image forming apparatus for determining a consumption amount . A toner saving method by an image forming apparatus having a plurality of image forming means each having a different image forming color,
A color pixel determination step for determining an input color that is all kinds of colors used in the input image data;
An image forming color selecting step for selecting the image forming color necessary for expressing all the colors determined in the color pixel determining step;
The number of the input color which is determined by the color pixel determination step, and, in response to the image forming colors required, see containing a toner saving step, the determining the amount of toner consumption of the image forming colors,
In the toner saving process,
When the number of input colors is 1 and the input color is black, the consumption amount of black toner is determined without toner saving;
When the number of the input colors is 1 and the input color is not black, a consumption amount of the toner of the image forming color that is necessary is determined using a lookup table that emphasizes contrast,
When the number of the input colors is 2 and one of the input colors is black, the toner saving unit uses a look-up table in which gradation is emphasized for black, and the other input Using a look-up table that emphasizes contrast for color, determine the amount of toner consumption of the image color required,
When the required image forming colors are all of the image forming colors possessed by the plurality of image forming units, a look-up table that emphasizes gradation is used to determine the toner of the required image forming colors. A toner saving method characterized by determining a consumption amount .

Images