JP5400278B2 - Image processing apparatus, image processing method, and program - Google Patents

Description

  The present invention relates to an image processing apparatus such as an electrophotographic method, and an image processing method in the image processing apparatus. In particular, the present invention relates to an image processing apparatus and an image processing method for reducing the amount of recording material without degrading an image.

In an electrophotographic printer (including an apparatus having a printer unit such as a copying machine), if the amount of toner as a recording material exceeds a certain value, toner fixing failure or toner scattering may occur. . Due to poor fixing and toner scattering, not only the image quality is impaired, but also the printer apparatus main body is damaged. Therefore, the amount of toner has been reduced by image processing before image formation. The reduction in toner amount is also called TOR. As one of the methods for reducing the toner amount, when the color conversion processing unit converts the color system from L * a * b * which is the standard color system to CMYK which is the color system of the output device, A method for manipulating the values of the conversion table has been proposed (see, for example, Patent Document 1). In Patent Document 1, in order to convert from L * a * b * to CMYK, a color conversion table in which values of CMYK colors corresponding to L * a * b * grid points are registered is used. In this color conversion table, the value of each color of C, M, Y, and K is set so that the total amount of output colors of the grid points is smaller than the limit value allowed at the time of output (for example, 250% with the maximum value being 100%). Is registered. Since an amount of recording material corresponding to the value of the pixel value is used during image formation, the above processing prevents the total value of CMYK after color conversion from exceeding the limit value and reduces the amount of ink and toner. The
JP 9-247471 A

  However, in the conventional image processing apparatus, the amount of toner is further reduced in the process of actually printing after finishing the toner reduction. This is because, in the electrophotographic method, the input pixel value (for example, density value) and the density of the image formed with respect to the pixel value do not have a linear relationship. In order to linearly correct the nonlinearity between the input pixel value and the image density, conversion of the input pixel value is performed. This conversion further reduces the toner amount. Hereinafter, this conversion is referred to as print gradation correction. Printing tone correction includes gamma correction and correction of changes in printer output density over time. In the electrophotographic system, as the time elapses, an image formed tends to have a higher density than the density to be expressed. For this reason, non-linear conversion is performed on the input pixel value so as to lower the density, particularly the intermediate density, by performing print tone correction. That is, the conversion characteristics of the print tone correction with the input pixel value on the horizontal axis and the output pixel value on the vertical axis draws a concave curve to reduce the input pixel value.

  Therefore, if toner reduction is performed before print gradation correction, the pixel value reduced by toner reduction is further reduced by subsequent print gradation correction. 4 and 5 show examples of toner amounts when a single color input image is printed such that the sum of the pixel values of each color component is 300 percent of the maximum value of each color component. FIG. 4 is a diagram showing the total amount of CMYK toner when toner reduction is not performed. FIG. 5 is a diagram showing the total amount of CMYK toner when toner reduction is performed.

  In the case of FIG. 4, even if the total value of each color component (CMYK) of the input pixel value is 300% of the maximum value of each color component, it becomes 200% by the print gradation correction. If the limit value is 250%, the density is converted to a density equal to or lower than the limit value without toner reduction.

  On the other hand, in the case of FIG. 5, if the total value of each color component of the input pixel value is 300% of the maximum value of each color component, it exceeds the limit value 250%, so toner reduction is performed. As a result, the sum of the pixel values of each color component is converted to a value equal to or less than the limit value, that is, 250%. The pixel value is further reduced to 180% by the subsequent print gradation correction. That is, the toner amount is excessively reduced. The excessive toner amount reduction processing deteriorates the gradation of the image data and degrades the quality of the formed image.

  In the toner reduction technique described above, in consideration of the final reduction of the toner amount, even if the toner reduction process is performed using a temporary limit value larger than the original limit value as a threshold, the toner is strictly within the limit value. It is difficult to reduce the amount.

  The present invention has been made in view of the above-described conventional example, and an object thereof is to provide an image processing apparatus and an image processing method that solve the above problems. That is, an object of the present invention is to provide an image processing apparatus and an image processing method that can prevent image deterioration caused by excessive limitation of the toner amount.

In order to achieve the above object, the present invention comprises the following arrangement. In other words, according to the first aspect of the present invention, gradation correction processing is performed using a gradation target having a characteristic that an output value with respect to an input value is reduced for each color component value of each pixel constituting image data. 1 gradation correction processing means;
A comparison means for comparing a total value of each color component value corrected by the first gradation correction processing means with the limit value after the first gradation correction processing;
As a result of the comparison by the comparison means, if the total value of the color component values after the first gradation correction processing is greater than the limit value, the color components are set so that the total value is less than or equal to the limit value. Control means for controlling the value;
For each color component values controlled by the control means, using the input-output characteristic having a characteristic that the output value increases with respect to the input values have a second gradation correction processing means for performing gradation correction processing,
Input-output characteristic having a characteristic that the output value for the input value is increased, Ru inverse characteristic der of the gradation target.

Alternatively, according to a second aspect of the present invention, the output value of the color conversion table for converting the input image data of the first color system to the output image data of the second color system is the output value. First gradation correction processing means for performing gradation correction processing using a gradation target having a characteristic of reducing
Comparison means for comparing a total value of each color component value of the output value after the first gradation correction processing corrected by the first gradation correction processing means with a limit value;
As a result of the comparison by the comparison means, if the total value of the color component values after the first gradation correction processing is greater than the limit value, the color components are set so that the total value is less than or equal to the limit value. Control means for controlling the value ;
For each color component values controlled by the control means, using the input-output characteristic having a characteristic that the output value increases with respect to the input values have a second gradation correction processing means for performing gradation correction processing,
Input-output characteristic having a characteristic that the output value for the input value is increased, Ru inverse characteristic der of the gradation target.

Alternatively, a third aspect of the present invention is a density adjustment processing unit that performs density adjustment processing on image data;
First tone correction for performing tone correction processing on each color component value of each pixel constituting the density-adjusted image data using a tone target having a characteristic that an output value with respect to an input value decreases. Processing means;
A comparison means for comparing a total value of each color component value corrected by the first gradation correction processing means with the limit value after the first gradation correction processing;
As a result of the comparison by the comparison means, if the total value of the color component values after the first gradation correction processing is greater than the limit value, the color components are set so that the total value is less than or equal to the limit value. Control means for controlling the value ;
For each color component values controlled by the control means, using the input-output characteristic having a characteristic that the output value increases with respect to the input values have a second gradation correction processing means for performing gradation correction processing,
Input-output characteristic having a characteristic that the output value for the input value is increased, Ru inverse characteristic der of the gradation target.
Alternatively, according to a fourth aspect of the present invention, density adjustment processing is performed on an output value of a color conversion table for converting input image data of the first color system to output image data of the second color system. Density adjustment processing means to perform;
A first gradation correction for performing gradation correction processing on each color component value of the output value after the density adjustment processing by the density adjustment processing unit using a gradation target having a characteristic that the output value with respect to the input value decreases. Processing means;
A comparison means for comparing a total value of each color component value corrected by the first gradation correction processing means with the limit value after the first gradation correction processing;
As a result of the comparison by the comparison means, if the total value of the color component values after the first gradation correction processing is greater than the limit value, the color components are set so that the total value is less than or equal to the limit value. Control means for controlling the value ;
For each color component values controlled by the control means, using the input-output characteristic having a characteristic that the output value increases with respect to the input values have a second gradation correction processing means for performing gradation correction processing,
Input-output characteristic having a characteristic that the output value for the input value is increased, Ru inverse characteristic der of the gradation target.

  According to the above configuration, it is possible to prevent an excessive toner amount from being reduced and to prevent image quality deterioration caused by the excessive toner amount reduction. In addition, the image quality adjustment after the toner reduction and the reflection of the gamma correction can prevent toner scattering and fixing failure due to the toner exceeding the limit value.

[First Embodiment]
The details of the toner amount reduction in the image processing apparatus according to the embodiment of the present invention will be described below with reference to the drawings. Before that, first, the correspondence between the configuration of the present invention and the configuration in the embodiment will be described.

  First, the calculation A process executed in the toner amount control processing unit and the toner amount calculation process at the time of output correspond to the calculation unit (calculation step). The calculation unit (calculation step) calculates recording material amount data representing the recording material amount necessary for forming the image based on the image data representing the image in each embodiment. The calculation A is performed in S702_2 in FIG. 7-2, S802_2 in FIG. 8-2, and S904_2 in FIG. 9-2. In this embodiment, the recording material amount is toner, particularly YMCK color toner. The YMCK color component value, including the corrected value, corresponds to recording material amount data representing the recording material amount. Further, the toner amount reduction processing executed in the toner amount control processing unit corresponds to a reduction processing unit (reduction process). The reduction processing unit (reduction process) sets a value corresponding to the reduced recording material amount when it is determined that the recording material amount needs to be reduced based on the recording material amount data calculated by the calculation unit. The recording material amount data is changed. This process is performed in S704_2 in FIG. 7-2, S804_2 in FIG. 8-2, and S906_2 in FIG. 9-2. Further, the inverse operation (referred to as inverse operation A) of the operation A executed in the toner amount control processing unit corresponds to the inverse operation unit (inverse operation step). The inverse operation unit (inverse operation step) performs an inverse operation of the operation performed by the operation unit on the recording material amount data after the processing by the reduction processing unit. Further, the printer unit corresponds to an image forming unit that performs image formation, that is, printing based on the recording material amount data that has been subjected to the reverse operation by the reverse operation unit. This process is performed in S705_2 in FIG. 7-2, S805_2 in FIG. 8-2, and S907_2 in FIG. 9-2.

  The recording material amount data is data indicating the value, that is, the density of each color component YMCK for each pixel constituting the image. The YMCK value is subjected to correction processing, for example, gamma correction, by the color conversion processing unit of each embodiment in order to correct the input / output characteristics of the toner. However, this processing can also be executed by the arithmetic unit described above. A module that performs this correction processing is particularly called a correction unit or a gamma correction unit.

  Further, output correction for correcting the density characteristics of image formation by the printer unit may be performed together with or selectively with gamma correction. In this case, the recording material amount data obtained in the toner amount control processing unit is density data indicating the density of each color component subjected to gamma correction and / or output correction.

  In addition, RGB corresponds to the first color system, and YMCK corresponds to the second color system. In the present embodiment, the first color system is a color system of input image data. The second color system is a table system of output image data. Also, the 3DLUT update process shown in FIGS. 8-2 and 9-2 corresponds to an update unit (update process). The update unit updates the color conversion table for converting from the first color system to the second color system based on the recording material amount data subjected to the reverse operation by the reverse operation unit.

  Further, the linear gain calculation (S901_2) and the fine density adjustment calculation (S902_2) shown in FIG. 9-2 correspond to a color adjustment unit (color adjustment step).

  Furthermore, S701_2 in FIG. 7-2, S801_2 in FIG. 8-2, and S903_2 in FIG. 9-2 correspond to a calculation means (calculation step). The calculation means calculates color material amount data for each pixel constituting the image data. The calculation means (calculation step) corresponds to the calculation A in S702_2 in FIG. 7-2, S802_2 in FIG. 8-2, and S904_2 in FIG. 9-2. The calculation means performs an output gradation correction process on the color material amount data, and calculates the color material amount data after the output gradation correction process. Further, S704_2 in FIG. 7-2, S804_2 in FIG. 8-2, and S906_2 in FIG. 9-2 correspond to control means (control process). The control means (control process) controls the color material amount data calculated by the calculation means to be equal to or less than the limit value based on the color material amount data calculated by the calculation means and the limit value of the color material amount. . S705_2 in FIG. 7-2, S805_2 in FIG. 8-2, and S907_2 in FIG. 9-2 correspond to inverse calculation means. The inverse operation means executes an inverse operation A of the operation A performed by the operation means on the color material amount data controlled by the control means.

<Configuration of image processing apparatus>
FIG. 1 is a schematic block diagram of an image processing apparatus according to an embodiment of the present invention. In the following, a digital multi-function peripheral or the like is assumed as an image processing apparatus in the embodiment, but the same can be considered for other printing devices such as a color printer as well as a copying machine.

  First, the structure of the image processing apparatus according to the present embodiment will be described. As shown in FIG. 1, the image processing apparatus 100 includes an image reading unit 101, an image processing unit 102, a storage unit 103, a CPU 104, an image output unit 105, a UI 106, and an image receiving unit 107. The image processing apparatus can also be connected to a server that manages image data, a personal computer (PC) that instructs the image processing apparatus to execute printing, via a network such as a LAN or the Internet. .

  Next, the operation of each component of the image processing apparatus shown in FIG. 1 will be described. The image reading unit 101 reads an input image. For example, the image reading unit 101 reads a CMYK color image or the like. Next, the image processing unit 102 converts the received print information into intermediate information (hereinafter referred to as “object”) and stores it in the object buffer. At this time, image processing such as density correction is performed. Further, the image processing unit 102 generates bitmap data based on the buffer object and stores the bitmap data in the band buffer. At this time, dither processing, halftone processing, and the like are performed. The image processing unit 102 can also be configured by, for example, a CPU and a memory, and a program executed by the CPU to realize the above functions.

  Next, configurations and functions of the storage unit 103, the CPU 104, and the image output unit 105 of the image processing apparatus illustrated in FIG. 1 will be described. The storage unit 103 includes various storage media such as a random access memory (RAM) and a read only memory (ROM). For example, the RAM is used as an area for storing data and various types of information or as a work area. On the other hand, the ROM is used as an area for storing various control programs. The CPU 104 is used to determine and control various processes according to a program stored in the ROM. Further, the image output unit 105 has a function of outputting an image (for example, forming and outputting an image on a recording medium such as printing paper).

  FIG. 10 is a diagram schematically illustrating a hardware configuration of the image reading unit (101), the image receiving unit (102), and the image output unit (106) of the image processing apparatus in FIG. 1, and a cross-sectional view of the image processing apparatus. Show. A more detailed configuration of the image processing apparatus described with reference to FIG. 1 will be described with reference to FIG. This image processing apparatus has functions of a copy, a printer, and a facsimile. 10, the image processing apparatus according to the present embodiment includes a scanner 301, a document feeder (DF) 302, a print recording printer 310 including a color four-color drum, a paper feed deck 314, a finisher 315, and the like.

  First, a reading operation performed mainly by the scanner 301 will be described. When a document is set on the document table 307 and read, the user sets the document on the document table 307 and closes the DF 302. Then, after the open / close sensor 350 detects that the document table 307 is closed, the light reflection type document size detection sensors 331 to 335 in the housing of the scanner 301 detect the set document size. Starting from this size detection, the light source 310 irradiates the original, and a charge-coupled device (CCD) 343 receives the reflected light from the original via the reflector 311 and the lens 312 to read the image. Then, the controller of the image processing apparatus converts the image data read by the CCD 34 into a digital signal, performs desired image processing, and converts it into a laser recording signal. The converted recording signal is stored in a memory in the controller.

  When a document is set on the DF 302 and read, the user places the document face up on the tray of the document setting unit 303 of the DF 302. Then, the document presence / absence sensor 304 detects that the document is set, and in response to this, the document feed roller 305 and the conveyance belt 306 rotate to convey the document, and the document is placed at a predetermined position on the document table 307. Is set. Thereafter, the image is read in the same manner as reading on the document table 307, and the obtained recording signal is stored in the memory in the controller.

  When the reading is completed, the conveyance belt 306 rotates again to feed the document to the right side in the cross-sectional view of the image processing apparatus in FIG. 10, and the document is discharged to the document discharge tray 309 via the discharge roller 308. Paper. When there are a plurality of documents, the documents are discharged from the document table 307 to the right side in the sectional view of the image processing apparatus, and at the same time, from the left side in the sectional view of the image processing apparatus via the sheet feeding roller 305. The original is fed, and the next original is continuously read. The above is the operation of the scanner 301.

  Next, a printing operation performed mainly by the printer 310 will be described. The recording signal (print image data) once stored in the memory in the controller is transferred to the printer 310 and converted into four-color recording laser light of Yellow, Magenta, Cyan, and Black by the laser recording unit. Then, the recording laser light is applied to the photosensitive members 316 of the respective colors, and an electrostatic latent image is formed on each photosensitive member. The printer 310 performs toner development on each photoconductor with the toner supplied from the toner cartridge 317, and the toner image visualized on each photoconductor is primarily transferred to the intermediate transfer belt 321. The intermediate transfer belt 321 rotates in the clockwise direction in FIG. 10, and the recording paper fed from the paper cassette 318 or the paper feed deck 314 through the paper feed conveyance path 319 reaches the secondary transfer position 320. The toner image is transferred from the intermediate transfer belt 321 to the recording paper.

  The recording paper onto which the image has been transferred is fixed with toner by pressurization and heat in a fixing device 322, and is conveyed through a paper discharge conveyance path. Then, the recording sheet is discharged to the face-down center tray 323, switched back to the discharge port 324 to the finisher, or the face-up side tray 325. However, the side tray 325 is a paper discharge port that can discharge paper only when the finisher 315 is not attached. The flappers 326 and 327 are for switching the transport path in order to switch these discharge ports. In the case of double-sided printing, after the recording paper passes through the fixing device 322, the flapper 327 switches the conveyance path, and then switches back and the recording paper is sent downward. The paper is fed to the position 320 and double-sided printing is performed.

  Next, operations performed by the finisher 315 will be described. The finisher 315 performs post-processing on the printed paper according to the function designated by the user. Specifically, it has functions such as staple (one place, two place binding), punch (two holes, three holes), and saddle stitching. The image processing apparatus of FIG. 10 has two paper discharge trays 328, and the recording paper that has passed through the paper discharge port 324 to the finisher 315 is discharged for each copy, printer, FAX function, for example, depending on user settings. The tray 328 is sorted. The print engine 310 is a color 4-drum printer, but may be a color 1-drum engine or a monochrome recording printer engine. When the image processing apparatus shown in FIG. 10 is used as a printer, monochrome / color printing, paper size, 2UP / 4UP printing / N-UP printing, double-sided, staple, punch, saddle stitching, slip sheet, and cover sheet are performed by a driver. Various settings such as back cover can be made.

<Toner reduction processing>
Next, a specific process for reducing the toner amount will be described. First, the toner amount reduction is shown in FIG. The “printer unit” in FIGS. 2-1 to 3-4 corresponds to the image output unit 105. Blocks other than the “printer unit” indicate functions performed by the image processing unit 102. The function of the image processing unit 102 may be implemented by hardware, but may be realized by a program having a procedure shown in the figure. In this case, “part” in FIGS. 2-1 to 3-4 means a “process” processed by the CPU. The same applies to FIGS. 7-1 to 9-2 and FIGS. 11-1 and 11-2.

  FIG. 2A is a schematic diagram illustrating a part of the processing of the image processing unit 102 and the processing of the image output unit 105. The unit A200_1 in the image processing unit 102 is a color conversion processing unit that performs color conversion processing from an RGB image that is a first color system to a CMYK image that is a second color system. The unit A 201_1 is a toner amount control processing unit that reduces the toner amount when the toner amount is larger than the limit value. The unit A 202_1 is a print gradation correction processing unit that performs gamma conversion and a temporal correction for correcting a change according to the elapsed time of the output density of the printer. The unit A 204_1 is an image processing unit 102 that performs various image processing such as the unit A 200_1 and the unit A 201_1.

  The unit A203_1 in the image output unit 105 is a printer unit that outputs based on the result of image processing.

FIG. 7-1 shows a processing flow according to the conventional method in the toner amount control processing unit A201_1 in FIG. Hereinafter, the processing flow of FIG. 7-1 will be described. The processing target is a pixel unit.
S700_1: Start.
S701_1: The current toner amount Toner_1 is calculated for the C, M, Y, and K values of the input pixel. For example, the total amount of C, M, Y, and K values of the input pixel is obtained as the current toner amount.
S702_1: The total value Toner_1 of C, M, Y, and K of the input pixel is compared with a predetermined limit value Limit_value. If the total value Toner_1 of C, M, Y, and K is larger, the process proceeds to S703_1. Otherwise (if less than the limit value), the process proceeds to S704_1.
S703_1: Toner amount reduction processing is performed to update the values of C, M, Y, and K, and the process proceeds to S702_1. For example, a predetermined ratio of CMY color values is replaced with a K component. As a result, the amount of CMY toner can be reduced.
S704_1: End.

  The above is the processing steps of the conventional method. In the conventional method, the toner amount is excessively reduced by print tone correction (gamma conversion, correction of change in output density of the printer over time, etc.) performed after the toner amount reduction. That is, in the conventional method, the toner amount control processing unit does not consider the toner reduction by the print gradation correction, and therefore the toner amount is excessively reduced. The gamma process is a process for linearly converting the input / output characteristics of the printer, so it is desirable to perform it after the color process. Furthermore, since toner reduction may cause irreversible loss of color components, it is desirable to perform color processing such as density adjustment after toner reduction.

Next, FIG. 7-2 shows a processing flow in the toner amount control processing unit A201_1 in FIG. 2-1 according to the embodiment of the present invention. Hereinafter, the processing flow of FIG. 7-2 will be described.
S700_2: Start.
S701_2: The current toner amount Toner_1 is calculated for the C, M, Y, and K values of the input pixel in the same manner as S701_1 in FIG. 7A, and the process proceeds to the next step. This process need not be performed.
S702_2: An operation A is performed on the C, M, Y, and K values of the input pixel using a gradation correction LUT (that is, a table), and the respective color component values C1, M1, Y1, and K1 at the time of printer output are calculated. To do. Then, the current toner amount Toner_2 is calculated. The toner amount Toner_2 is, for example, a total value of C1, M1, Y1, and K1. Then proceed to the next step. The gradation correction LUT is an LUT given in advance by gamma characteristics or calibration. For example, when the input / output data is 8 bits, the gradation correction LUT has an input / output characteristic of a downward convex curve as shown in FIG. That is, the value decreases by the conversion.
S703_2: The total value Toner_2 of the color component values C1, M1, Y1, and K1 at the time of printer output is compared with the limit value Limit_value, and if Toner_2 is larger, the process proceeds to S704_2, otherwise (if less than the limit value) ) The process proceeds to S705_2.
S704_2: The toner amount reduction process is performed in the same manner as S703_1 in FIG. 7A, and C1, M1, Y1, and K1 are replaced with the respective color component values after the toner amount reduction process, and the process proceeds to S703_2.
S705_2: C ′, M ′, Y ′, and K ′ are obtained using an LUT having a characteristic (reverse characteristic) opposite to that of the gradation correction LUT. If the characteristic of the gradation correction LUT is a downward convex curve as shown in FIG. 6, for example, when the input / output data is 8 bits, the inverse characteristic is the input characteristic of the upward convex curve as shown in FIG. It is an LUT.
S706_2: End.

This process is performed for all pixels to be processed. Various methods can be employed for the toner amount reduction processing step (S704_2). One of the methods is a toner amount reduction method shown in FIGS. FIG. 11A is a flowchart illustrating the steps of toner reduction, and FIG. 11B illustrates the processing (S1103_1) in the UCR unit in FIG. The processing in FIG. 11A will be described in order below.
S1100_1: Start.
S1101_1: The sum of signal values (here, CMYK) of all colors of the input pixel is obtained, and the value is defined as SUM.
S1102_1: It is checked whether or not the value SUM is larger than the limit value N. If N <SUM, the process proceeds to S1103_1, and if N ≧ SUM, the process proceeds to S1108_1.
S1103_1: The UCR (under color removal) process is performed, and the values for the new color components obtained as a result are set as C ′, M ′, Y ′, and K ′, respectively.
S1104_1: The sum of C ′, M ′, Y ′, and K ′ is obtained and set as a value SUM ′.
S1105_1: It is checked whether or not the value SUM ′ is larger than the limit value N. If N <SUM ′, the process proceeds to S1106_1. If N ≧ SUM ′, the process proceeds to S1107_1.
S1106_1: The black component value K ′ after removal of the under color is set as an output value K ″. Further, a value NK ′ obtained by subtracting the output black component K ′ (= K ″) from the limit value N is input to other inputs. According to the ratio of the color component values C ′, M ′, and Y ′, the values are divided into output values C ″, M ″, and Y ″.
S1107_1: The color component values C ′, M ′, Y ′, and K ′ after the undercolor removal are set as output color component values C ″, M ″, Y ″, and K ″.
S1108_1: The input color component values C, M, Y, and K are set as output color component values C ", M", Y ", and K".
S1109_1: End.

The UCR process S1103_1 in FIG. 11A is shown in FIG. 11B, and the flow is as follows.
S1100_2: Data is input from S1102_1. A value UCR is set to a minimum value among a half value (SUM-N) of a sum of input pixel values exceeding a limit value (SUM-N) and each of C, M, and Y color component values. Note that the operation of dividing by 2 is realized by 1-bit right shift.
S1101_2: As the value K ′ of the K component after toner reduction, a maximum value (2 ⁿ −1) that the K component value can take and a value obtained by adding the value UCR obtained in S1100_2 to the original K component value K The smaller value is set as a new value K ′ of the color component K.
S1102_2: The values obtained by subtracting the difference between the new K component value K ′ and the original K component value K (that is, the component from which the undercolor has been removed) from the original CMY values, respectively, C, M, The Y component values C ′, M ′, and Y ′ are assumed. Thereafter, the data is transferred to S1104_1.

  As described above, since the toner amount is controlled with respect to the toner amount at the time of output before the toner amount is reduced, excessive reduction of the toner amount can be prevented. The conventional method processing steps and the processing steps of this embodiment have been described above. Specific effects of the proposed method are shown below using examples.

<Example>
First, consider a conventional example. For example, when C, M, Y, K = (175, 175, 175, 175) and the limit value 640 (about 250%) in the toner application amount control unit (Example 1), the limit value 640 <the total input value = 175 × 4 = 700. Therefore, the toner amount reduction process is executed, and the total value of each color component is reduced to 640. Further, after the above processing, the total value of each color component is reduced to 510 by the effect of gradation correction through image processing, a device, or the like (approximately 20% signal value due to the effect of the gradation target at the signal value 175). ).

  When another value C, M, Y, K = (210, 220, 220, 50) (example 2) is input, the limit value 640 <the total input value = 210 + 220 + 220 + 50 = 700. Therefore, the toner amount reduction process is executed, and the total value of each color component is reduced to 640.

  Further, after the above processing, the total value of each color component is reduced to 610 by the effect of gradation correction through image processing, a device, etc. (When the signal value is Example 2, the effect by the gradation target is about 5 % Signal value decreases).

  Therefore, in the conventional method, when the input value exceeds the limit value, the toner amount is excessively reduced from the limit value.

  On the other hand, in the method of this embodiment, first, the toner amount at the time of printer output is calculated in the toner amount control processing unit. For this purpose, a value at the time of toner output is calculated using an LUT having characteristics of a gradation target (hereinafter, an operation for this calculation is referred to as an operation A. S702_2 in FIG. 7-2). Next, the toner amount is reduced, and finally the inverse operation of the operation A is performed (S705_2 in FIG. 7-2). Here, the operation A is an operation by the LUT having the effect of the gradation target.

  By performing the processing as described above, the toner amount can be controlled with the density at the time of printer output. The effect of the invention will be described in the above example. In the case of Example 1, first, the value at the time of toner output is calculated using the LUT having the characteristics of the gradation target. Due to the effect of the gradation target, the total input value is 700 to 560. That is, this calculation A does not increase the density value indicated by the image data. Next, the limit value 640 is compared with the magnitude. Since limit value = 640> total input value = 560, toner amount control does not work. Finally, the signal value is restored using an LUT having the inverse characteristics of the gradation target. As a result, the total value of the color component values becomes 560 → 700. That is, this inverse operation A does not decrease the density value indicated by the image data.

  Here, due to the processing after the toner amount control processing unit (print gradation correction including gamma correction), the signal value of 700 becomes 560 at the time of printer output, and toner scattering and fixing failure due to too high density occur. It becomes difficult.

  Similarly, when the processing is performed in Example 2, the total input value becomes 700 to 665 due to the effect of the gradation target. Since limit value = 640 <total input value = 665, toner reduction processing is performed. The total pixel value is converted from 665 to 640 by the effect of the toner reduction process. Finally, using a LUT having the inverse characteristics of the gradation target, for example, the sum of pixel values is converted from 640 to 670.

  Here, by the print tone correction performed after the toner amount control processing unit, the total of the respective color component values is changed from 670 to 640 at the time of printer output, and toner scattering and fixing failure are less likely to occur.

  As described above, the toner is not excessively reduced with respect to the limit value as compared with the prior art, and a wider gradation can be expressed.

[Second Embodiment]
Next, as a second embodiment, an embodiment in which toner reduction is performed simultaneously with color conversion will be described. The configuration of the apparatus is the same as that of the first embodiment as shown in FIG.

  The conventional method and the proposed method will be described in the case where the toner amount reduction in this embodiment is performed in the toner amount control processing unit 3DLUT update processing unit A201_2 in the color conversion processing unit A200_2 shown in FIG. The color conversion processing unit is included in the image processing unit 102. FIG. 2B is a schematic diagram illustrating a part of the processing of the image processing unit 102 and the processing of the image output unit 105.

  The unit A 200_2 in the image processing unit 102 is a color conversion processing unit that performs color conversion processing from an RGB image to a CMYK image. The unit A201_2 has a toner amount control processing unit for limiting the reduction of the toner amount when the toner amount of the CMYK data read in the unit A200_2 is larger than the limit value, and updates the CMYK data when the reduction is performed. 3DLUT update processing unit. A unit A202_2 is a print gradation correction processing unit that performs gamma conversion and a temporal correction that corrects a change in the output density of the printer with the passage of time, and A203_2 is a printer unit that outputs based on the image processing result.

  When the toner conversion is performed in the color conversion processing unit A200_2 in FIG. 2-2, the 3DLUT update processing unit A201_2 is controlled by the CPU 104 (or the CPU built in the image processing unit 102).

The processing flow of the 3DLUT update processing unit A201_2 in FIG. 2-2 according to the conventional method is FIG. 8_1. Hereinafter, the processing flow of FIG. 8_1 will be described.
S800_1: Start.
S801_1: The CMYK values corresponding to the input RGB values are read from the three-dimensional LUT, and the current toner amount Toner_1 is calculated for the read C, M, Y, K values. For example, the total amount of C, M, Y, and K values of the input pixel is obtained as the current toner amount.
S802_1: The sum of C, M, Y, and K of the input pixel is compared with the limit value Limit_value of the predetermined toner amount. If the sum of C, M, Y, and K is large, the process proceeds to S803_1; If it is equal to or less than the limit value), the process proceeds to S804_1.
S803_1: Toner amount reduction restriction processing is performed to obtain C ′, M ′, Y ′, and K ′, and the process proceeds to S802_1. For example, a predetermined ratio of C, M, and Y color values is replaced with a K component. As a result, the amounts of C, M, and Y toners can be reduced.
S804_1: When the toner amount of the C, M, Y, and K values read in S801_1 is equal to or less than the limit value, the C, M, Y, and K values are updated as they are. When the toner amount of the C, M, Y, and K values read in S801_1 is larger than the limit value, the C ′, M ′, Y ′, and K ′ values obtained in S803_1 are updated.
S805_1: End.

  In this conventional method, as in the conventional method described in the first embodiment, since the toner amount at the time of print output is not calculated in the toner reduction process, the toner amount is excessively reduced.

Here, FIG. 8-2 shows processing steps of toner amount reduction by the proposed method in the present embodiment in the color conversion processing unit A206_2 in FIG. 2-2.
S800_2: Start.
S801_2: The current toner amount Toner_1 is calculated based on the values of C, M, Y, and K.
S802_2: A calculation A is performed on the input C, M, Y, and K values using the gradation correction target LUT, and the respective color component values C1, M1, Y1, and K1 at the time of printer output are calculated. Then, the current toner amount Toner_2 is calculated. The toner amount Toner_2 is, for example, a total value of C1, M1, Y1, and K1. Then proceed to the next step. The gradation correction target LUT is an LUT given in advance by gamma characteristics or calibration. For example, when the input / output data is 8 bits, the gradation correction target LUT has an input / output characteristic of a downward convex curve as shown in FIG. That is, the value decreases by the conversion.
S803_2: The sum of C, M, Y, and K obtained in S802_2 is compared with the limit value Limit_value of the predetermined toner amount. If the sum of C, M, Y, and K is large, the process proceeds to S806_2, otherwise. If it is equal to or less than the limit value, the process proceeds to S807_2.
S804_2: A toner amount reduction restriction process is performed to obtain C ′, M ′, Y ′, and K ′, and the process proceeds to S803_2. For example, a predetermined ratio of C, M, and Y color values is replaced with a K component. As a result, the amount of CMY toner can be reduced.
S805_2: Inverse characteristic LUT having characteristics opposite to the gradation target correction LUT (for example, when input / output data is 8 bits, it has an input / output characteristic of an upward convex curve as shown in FIG. 12).
Is used to perform inverse operation A to obtain C ′, M ′, Y ′, K ′.
S806_2: When the toner amount of the C, M, Y, and K values read in S805_2 is smaller than the limit value, the 3DLut value is updated while keeping the C, M, Y, and K values. On the other hand, when the toner amount of the C, M, Y, and K values read in S805_2 is larger than the limit value, the 3DLut value is updated to the C ′, M ′, Y ′, and K ′ values obtained in S806_2.
S807_2: End.

  Further, as the toner amount reduction method in step S804_2, the method shown in FIGS. 11A and 11B may be used as in the first embodiment.

  According to the above method, the toner amount when being output from the printer is taken into consideration when the toner amount is reduced, so that the toner amount can be appropriately reduced.

  According to the present embodiment, since toner reduction can be performed simultaneously with color conversion, the same effects as in the first embodiment can be obtained, and the processing burden can be reduced compared to the first embodiment.

  In the present embodiment, it is desirable that the color conversion LUT is not executed every time but is executed in a fixed processing unit or asynchronously with the printing process. That is, A201_2 in FIG. 2-2 is executed periodically or at a time designated by the user, and the obtained pre-change 3DLUT is stored. At the time of outputting an image, A201_2 is skipped, and the process is executed from A200_2. By doing so, it is possible to reduce the processing burden of calculating the LUT every time image processing is performed. In this case, toner amount reduction processing is performed on the entire input RGB of the LUT.

[Third Embodiment]
Next, the conventional method and the proposed method will be described in the case where the toner amount control process is performed after the color conversion process. First, the conventional method is the method shown in FIGS. The configuration of the apparatus is the same as in the first and second embodiments.

  The unit A300_1 is a color conversion processing unit that performs color conversion processing from an RGB image to a CMYK image. The unit A301_1 is a toner amount control processing unit that reduces the toner amount when the toner amount is larger than the limit value. The unit A302_1 is a density adjustment processing unit that performs image quality adjustment processing such as density adjustment. The unit A303_1 is a density fine adjustment processing unit that performs density adjustment according to the density range. The unit A304_1 is a print gradation correction processing unit that performs gamma conversion and a temporal correction for correcting a change according to the elapsed time of the output density of the printer. The unit A305_1 is a printer unit that outputs based on the result of image processing. The unit A306_1 is an image processing unit that performs various image processes such as a color conversion processing unit A300_1 and a toner amount restriction processing unit A301_1. Unit A307_1 is a UI unit for the user to make various settings.

  Here, the processing steps of the toner amount reduction by the proposed method in the toner amount control processing unit A301_1 in FIG. 3A are FIG. 7A, which are the same as the steps described in the first embodiment. . In this conventional method, there is a possibility that the density increases beyond the limit value by performing the image quality adjustment function after the toner amount control. Here, the proposed method is shown in FIGS. 3-2 and 7-2.

  The unit A300_2 is a color conversion processing unit that performs color conversion processing from an RGB image to a CMYK image. The unit A301_2 is a density adjustment processing unit that performs image quality adjustment processing such as density adjustment. The unit A302_2 is a density fine adjustment processing unit that performs density adjustment according to the density range. The unit A303_2 is a toner amount control processing unit that reduces the toner amount when the toner amount is larger than the limit value. The unit A304_2 is a print gradation correction processing unit that performs gamma conversion and a temporal correction for correcting a change according to the elapsed time of the output density of the printer. The unit A305_2 is a printer unit that outputs based on the result of image processing. The unit A306_2 is an image processing unit that performs various image processing such as a color conversion processing unit A300_2 and a toner amount restriction processing unit A302_2. The unit A307_2 is an operation unit (or UI unit) on which the user performs various settings.

  Here, the processing steps of the toner amount reduction by the proposed method in the present embodiment in the toner amount control processing unit A301_1 in FIG. 3A are FIG. 7-2, and this is the step described in the first embodiment. Is the same. In this proposed method, the density does not increase beyond the limit value by performing the image quality adjustment function before the toner amount control.

[Fourth Embodiment]
Finally, an embodiment for reducing the toner amount when an image quality adjustment function such as density adjustment is added in the second embodiment will be described. The configuration of the apparatus is the same as in the first, second, and third embodiments. First, processing performed conventionally will be described with reference to FIGS. 3-3 and 9-1.

  FIG. 3C is a schematic diagram showing a conventional processing flow of the image processing unit 102 and the image output unit 105 when an image quality adjustment function such as density adjustment is added. Here, the user sets an image quality adjustment function such as a fine density adjustment in the operation unit A307_3 (corresponding to the user interface 106). Then, the information is sent to the 3DLut update processing unit A301_3 in the color conversion processing unit A300_3, and 3DLut update processing is performed according to the setting of the image quality adjustment function.

  The unit A300_3 is a color conversion processing unit that performs color conversion processing from an RGB image to a CMYK image. The unit A301_3 is a 3DLut update processing unit that rewrites and updates 3DLut for converting an RGB image into a CMYK image. The unit A302_3 is a density adjustment processing unit that performs image quality adjustment processing such as density adjustment. The unit A303_3 is a density fine adjustment processing unit that performs density adjustment according to the density range. A unit A304_3 is a printing gradation correction processing unit that performs gamma conversion and correction with time to correct a change with time of the output density of the printer. The unit A305_3 is a printer unit that outputs based on the result of image processing. The unit A306_3 is an image processing unit that performs various types of image processing such as a color conversion processing unit A300_3 and a density adjustment processing unit A302_3. Unit A307_3 is a UI unit for the user to perform various settings.

Processing flow by the UI unit 106 corresponding to the image processing unit 102 and the operation unit A307_3 including the color conversion processing unit A300_3, the toner amount control processing unit A301_3, the density adjustment processing unit A302_3, and the density fine adjustment processing unit A303_3 in FIG. Fig. 9-1. Hereinafter, the processing flow of FIG. 9-1 will be described.
S900_1: Start S901_1: The CMYK values corresponding to the input RGB values are read from the three-dimensional LUT, and the current toner amount Toner_1 is calculated for the read C, M, Y, K values. For example, the total amount of C, M, Y, and K values of the input pixel is obtained as the current toner amount.

S902_1: The sum of C, M, Y, and K of the input pixel is compared with a limit value Limit_value of a predetermined toner amount. If the sum of C, M, Y, and K is large, the process proceeds to S903_1; If it is equal to or less than the limit value), the process proceeds to S904_1.
S903_1: A toner amount reduction restriction process is performed to obtain C ′, M ′, Y ′, and K ′, and the process proceeds to S902_1. For example, a predetermined ratio of C, M, and Y color values is replaced with a K component. As a result, the amount of CMY toner can be reduced.
S904_1: Linear gain calculation is performed according to the setting of the operation unit of A900_1.
S905_1: For the C, M, Y, and K values obtained in S904_1, the high density part, the medium density part, and the low density part are nonlinearly adjusted according to the setting of the operation part.
S906_1: The CMYK value corresponding to the input RGB value is updated to the value obtained in S901_1.
S907_1: End.

  The process ends as described above. As can be seen from the above steps, the toner amount was not reduced after image quality adjustment. Therefore, the amount of toner may exceed the limit value. For this reason, there is a risk of toner scattering and fixing failure. In some cases, the toner amount is excessively reduced.

  Next, processing performed according to the fourth embodiment of the present invention will be described with reference to FIGS. 3-4 and 9-2. FIG. 3-4 is a schematic diagram illustrating a flow of processing of the image processing unit 102 and processing of the image output unit 105 according to the method of the present embodiment when an image quality adjustment function such as density adjustment is added. In the method of this embodiment, image quality adjustment is performed before the toner amount is reduced.

  The unit A300_4 is a color conversion processing unit that performs color conversion processing from an RGB image to a CMYK image. The unit A301_4 is a 3DLut update processing unit that rewrites and updates 3DLut for converting an RGB image into a CMYK image. The unit A302_4 is a print gradation correction processing unit that performs gamma conversion and a temporal correction for correcting a change according to the elapsed time of the output density of the printer. The unit A305_3 is a printer unit that outputs based on the result of image processing.

The processing flow of the UI unit of the color conversion processing unit A300_4 and the operation unit A305_4 of FIG. 3-4 is illustrated in FIG. 9-2. Hereinafter, the processing flow of FIG. 9-2 will be described.
S900_2: Start.
S901_2: CMYK values corresponding to the input RGB values are read from the three-dimensional LUT, and linear gain calculation is performed on the read C, M, Y, and K values according to the setting of the operation unit A303_2.
With respect to the values of C, M, Y, and K obtained in S902_2, the high density part, the medium density part, and the low density part are nonlinearly adjusted according to the setting of the operation unit.
S903_2: The current toner amount Toner_1 is calculated. For example, the total amount of C, M, Y, and K is obtained as the current toner amount.
S904_2: A calculation A is performed on the C, M, Y, and K values sent from S903_2 using the gradation target correction LUT, and the respective color component values C1, M1, Y1, and K1 at the time of printer output are calculated. Then, the toner amount Toner_2 is calculated. The toner amount Toner_2 is, for example, a total value of C1, M1, Y1, and K1. Then proceed to the next step. The gradation correction target LUT is an LUT given in advance by gamma characteristics or calibration. For example, when the input / output data is 9 bits, the gradation correction target LUT has an input / output characteristic of a downward convex curve as shown in FIG. For this reason, a value decreases by conversion.
S905_2: The total value Toner_2 of C, M, Y, and K obtained in S904_2 is compared with a limit value Limit_value of a predetermined toner amount. If the total value Toner_2 of C, M, Y, and K is larger, the process proceeds to S906_2, and if not (if not greater than the limit value), the process proceeds to S907_2.
S906_2: A toner amount reduction restriction process is performed to obtain C ′, M ′, Y ′, and K ′, and the process proceeds to S905_2. For example, a predetermined ratio of C, M, and Y color values is replaced with a K component. As a result, the amount of CMY toner can be reduced.
S907_2: C ′, M ′, Y ′, and K ′ are obtained by using an inverse characteristic LUT having a characteristic opposite to that of the gradation target correction LUT. For example, when the input / output data is 9 bits, the inverse characteristic LUT has an input / output characteristic of an upwardly convex curve as shown in FIG.
S908_2: When it is determined in S905_2 that the total value Toner_2 of the read CMYK values is equal to or less than the limit value, the 3DLut value is updated without performing the toner amount reduction process. On the other hand, when the toner amount of the CMYK value read in S905_2 is larger than the limit value, the 3DLut value is updated to the C ′, M ′, Y ′, and K ′ values obtained in S906_2.
S909_2: End.
The process ends as described above.

Specific processing in steps S901_2 and S902_2 will be described below. In the density adjustment processing in step S901_2, linear gain calculation is performed for each of C, M, Y, and K, and the calculation formula is as follows.
Y = (X + offset) * Gain / Div.
Here, offset, Gain, and Div are parameters that can be set independently by the user for C, M, Y, and K, respectively. X and Y are input and output, respectively.

In the density fine adjustment process in step S902_2, the low density area S, the middle density area M, and the high density area H are nonlinearly adjusted for each of C, M, Y, and K as shown in the following equation.
Y = X + ΔH (X) * fH (v) + ΔM (x) * fM (v) + ΔS (x) * fS (v).
Note that v is an integer of −8 to +8, and f is a modulation amount.

  Further, in the toner amount reduction method in step S704_2, the methods shown in FIGS. 11A and 11B may be used as in the first and second embodiments.

  As described above, even when the image quality adjustment function such as density adjustment is adjusted, it is possible to prevent the toner amount from exceeding the limit value, and it is possible to prevent the occurrence of toner scattering and fixing failure. In addition, excessive toner reduction can be prevented and image quality deterioration can be prevented.

[Other Embodiments]
The present invention can take the form of, for example, a system, apparatus, method, program, or storage medium (recording medium). Specifically, the present invention is applied to a system composed of a plurality of devices. Alternatively, the present invention may be applied to an apparatus composed of a single device. This storage medium is a computer-readable storage medium.

  The present invention can also be achieved by supplying a program that realizes the functions of the above-described embodiment directly or remotely to a system or apparatus, and the computer of the system or apparatus reads and executes the supplied program code. Including the case where it is achieved. In the embodiment, the program is a software program corresponding to the flowchart shown in the drawing.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, or the like.

  Examples of the recording medium for supplying the program include a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a magnetic tape, a nonvolatile memory card, and a ROM. Optical disks include, for example, CD-ROM, CD-R, CD-RW, DVD (DVD-ROM, DVD-R) and the like.

  In addition, the program can be supplied by connecting to a specific server on the Internet using a browser of a client computer and downloading the computer program of the present invention from the server. The program may be compressed or supplied as a file including an automatic installation function. The downloaded program is stored in a recording medium such as a hard disk. It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the present invention.

  Further, the program of the present invention may be encrypted and stored in a storage medium such as a CD-ROM and distributed to users. This is realized by having a user who has cleared a predetermined condition download key information to be decrypted from a homepage via the Internet, execute the encrypted program by using the key information, and install it on a computer. It is also possible.

  Further, the function of the above-described embodiment can be realized by an OS or the like running on the computer based on an instruction of the read program, by performing part or all of the actual processing.

  Furthermore, the present invention is also applied to the case where the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer. In that case, based on the instruction of the written program code, the CPU of the function expansion card or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing. .

1 is a schematic block diagram of an image processing apparatus according to an embodiment of the present invention. FIG. 6 is a schematic diagram of image processing and device-side processing when toner amount reduction is performed after the color conversion processing unit in the first embodiment. FIG. 10 is a schematic diagram of image processing and device-side processing when toner amount reduction is performed in a color conversion processing unit according to the second embodiment. It is the schematic of the image process by a 3rd conventional method, and the process by the side of a device. It is the schematic of the image processing by the 3rd proposal method, and the process by the side of a device. It is the schematic of the image processing by a 4th conventional method, and the process by the side of a device. It is the schematic of the image process by the 4th proposal method, and the process by the side of a device. FIG. 6 is a diagram illustrating a change in an amount applied by a gradation target when toner control is OFF. FIG. 6 is a diagram illustrating a state in which a toner amount is reduced by both toner amount control and print gradation correction when toner control is ON. It is a figure which shows the graph of gradation correction | amendment Lut. It is a flowchart which shows the process step which reduces the toner amount of the 1st conventional method. FIG. 6 is a flowchart illustrating processing steps for reducing the toner amount according to the first embodiment. FIG. 10 is a conventional flowchart for reducing the amount of toner in a color conversion processing unit according to a second conventional method. It is a flowchart of the proposal when reducing the toner amount in the color conversion processing unit of the second proposed method. It is a flowchart which performs toner amount reduction when the image quality adjustment function in the 4th conventional method is performed. FIG. 10 is a flowchart for performing toner amount reduction when an image quality adjustment function is performed in a fourth embodiment. It is a figure which shows typically the hardware constitutions of the image reading part 101 of the image processing apparatus in FIG. 1, and the image output part 105. FIG. 10 is a flowchart of toner reduction processing for converting input image signal values C, M, Y, and K into C ″, M ″, Y ″, and K ″ limited to a limit value N. FIG. It is a figure which shows the process in UCR in FIG. 7 is a graph having characteristics opposite to those in FIG.

Explanation of symbols

101 Image Reading Device 102 Image Processing Unit 103 Storage Unit 104 CPU
105 image output unit 106 UI unit 107 image receiving unit 108 image reading unit

Claims (20)

First gradation correction processing means for performing gradation correction processing on each color component value of each pixel constituting image data using a gradation target having a characteristic that an output value with respect to an input value is reduced;
A comparison means for comparing a total value of each color component value corrected by the first gradation correction processing means with the limit value after the first gradation correction processing;
As a result of the comparison by the comparison means, if the total value of the color component values after the first gradation correction processing is greater than the limit value, the color components are set so that the total value is less than or equal to the limit value. Control means for controlling the value;
For each color component values controlled by the control means, using the input-output characteristic having a characteristic that the output value increases with respect to the input values have a second gradation correction processing means for performing gradation correction processing,
Input-output characteristic having a characteristic that the output value for the input value increases, the image processing apparatus according to claim inverse characteristic der Rukoto of the gradation target.   The control means performs a UCR process on each color component value after the first gradation correction process to reduce a total value of each color component value after the first gradation correction process. The image processing apparatus according to claim 1.   Further, a third step of performing print gradation correction processing for reducing each color component value for each color component value after the second gradation correction processing corrected by the second gradation correction processing means. The image processing apparatus according to claim 1, further comprising a tone correction processing unit.   4. The image processing apparatus according to claim 1, wherein the gradation target having a characteristic that an output value is reduced with respect to the input value has an input / output characteristic of a downward convex curve. 5.   5. The image processing apparatus according to claim 1, wherein the input / output characteristic having a characteristic of increasing an output value with respect to the input value is an input / output characteristic of an upwardly convex curve.   The image processing apparatus according to claim 3, wherein the print tone correction process is a temporal correction that corrects a change in the output density of the printer over time.   As a result of the comparison by the comparison unit, when the total value of the color component values after the first gradation correction processing is equal to or less than the limit value, the control unit does not perform the process of controlling the color component values. The image processing apparatus according to claim 1. A gradation target having a characteristic of reducing the output value is used for the output value of the color conversion table for converting the input image data of the first color system to the output image data of the second color system. First gradation correction processing means for performing gradation correction processing,
Comparison means for comparing a total value of each color component value of the output value after the first gradation correction processing corrected by the first gradation correction processing means with a limit value;
As a result of the comparison by the comparison means, if the total value of the color component values after the first gradation correction processing is greater than the limit value, the color components are set so that the total value is less than or equal to the limit value. Control means for controlling the value ;
For each color component values controlled by the control means, using the input-output characteristic having a characteristic that the output value increases with respect to the input values have a second gradation correction processing means for performing gradation correction processing,
Input-output characteristic having a characteristic that the output value for the input value increases, the image processing apparatus according to claim inverse characteristic der Rukoto of the gradation target. The control means performs a UCR process on each color component value after the first gradation correction process to reduce a total value of each color component value after the first gradation correction process. The image processing apparatus according to claim 8 . Further, a third step of performing print gradation correction processing for reducing each color component value for each color component value after the second gradation correction processing corrected by the second gradation correction processing means. The image processing apparatus according to claim 8 , further comprising a tone correction processing unit. The gradation target having a characteristic that the output value decreases with respect to the input value, the image processing apparatus according to any one of claims 8 to 10, characterized by having the input and output characteristics of the lower convex curve. The input-output characteristic having a characteristic that the output value increases with respect to the input value, the image processing apparatus according to any one of claims 8 to 11, characterized in that the input-output characteristic of the upward convex curve. The image processing apparatus according to claim 10 , wherein the print tone correction process is a temporal correction that corrects a change in the output density of the printer over time. Density adjustment processing means for performing density adjustment processing on image data;
First tone correction for performing tone correction processing on each color component value of each pixel constituting the density-adjusted image data using a tone target having a characteristic that an output value with respect to an input value decreases. Processing means;
A comparison means for comparing a total value of each color component value corrected by the first gradation correction processing means with the limit value after the first gradation correction processing;
As a result of the comparison by the comparison means, if the total value of the color component values after the first gradation correction processing is greater than the limit value, the color components are set so that the total value is less than or equal to the limit value. Control means for controlling the value ;
For each color component values controlled by the control means, using the input-output characteristic having a characteristic that the output value increases with respect to the input values have a second gradation correction processing means for performing gradation correction processing,
Input-output characteristic having a characteristic that the output value for the input value increases, the image processing apparatus according to claim inverse characteristic der Rukoto of the gradation target. Density adjustment processing means for performing density adjustment processing on an output value of a color conversion table for converting input image data of a first color system to output image data of a second color system;
A first gradation correction for performing gradation correction processing on each color component value of the output value after the density adjustment processing by the density adjustment processing unit using a gradation target having a characteristic that the output value with respect to the input value decreases. Processing means;
A comparison means for comparing a total value of each color component value corrected by the first gradation correction processing means with the limit value after the first gradation correction processing;
As a result of the comparison by the comparison means, if the total value of the color component values after the first gradation correction processing is greater than the limit value, the color components are set so that the total value is less than or equal to the limit value. Control means for controlling the value ;
For each color component values controlled by the control means, using the input-output characteristic having a characteristic that the output value increases with respect to the input values have a second gradation correction processing means for performing gradation correction processing,
Input-output characteristic having a characteristic that the output value for the input value increases, the image processing apparatus according to claim inverse characteristic der Rukoto of the gradation target. A first gradation correction processing step of performing gradation correction processing on each color component value of each pixel constituting image data using a gradation target having a characteristic that an output value with respect to an input value decreases;
A comparison step of comparing a total value of each color component value corrected by the first gradation correction processing step with a limit value.
As a result of the comparison in the comparison step, when the total value of the color component values after the first gradation correction processing is larger than the limit value, the color components are set so that the total value is equal to or less than the limit value. A control process for controlling the value;
For each color component values that is controlled by said control step, using the input-output characteristic having a characteristic that the output value increases with respect to the input values have a second gradation correction processing step of performing gradation correction processing,
Input-output characteristic having a characteristic that the output value for the input value increases, the image processing method comprising an inverse characteristic der Rukoto of the gradation target. A gradation target having a characteristic of reducing the output value is used for the output value of the color conversion table for converting the input image data of the first color system to the output image data of the second color system. A first gradation correction processing step for performing gradation correction processing,
A comparison step of comparing a total value of each color component value of the output value after the first tone correction processing corrected by the first tone correction processing step with a limit value;
As a result of the comparison in the comparison step, when the total value of the color component values after the first gradation correction processing is larger than the limit value, the color components are set so that the total value is equal to or less than the limit value. A control process for controlling the value ;
For each color component values that is controlled by said control step, using the input-output characteristic having a characteristic that the output value increases with respect to the input values have a second gradation correction processing step of performing gradation correction processing,
Input-output characteristic having a characteristic that the output value for the input value increases, the image processing method comprising an inverse characteristic der Rukoto of the gradation target. A density adjustment processing step for performing density adjustment processing on the image data;
First tone correction for performing tone correction processing on each color component value of each pixel constituting the density-adjusted image data using a tone target having a characteristic that an output value with respect to an input value decreases. Processing steps;
A comparison step of comparing a total value of each color component value corrected by the first gradation correction processing step with a limit value.
As a result of the comparison in the comparison step, when the total value of the color component values after the first gradation correction processing is larger than the limit value, the color components are set so that the total value is equal to or less than the limit value. A control process for controlling the value ;
For each color component values that is controlled by said control step, using the input-output characteristic having a characteristic that the output value increases with respect to the input values have a second gradation correction processing step of performing gradation correction processing,
Input-output characteristic having a characteristic that the output value for the input value increases, the image processing method comprising an inverse characteristic der Rukoto of the gradation target. A density adjustment processing step for performing density adjustment processing on an output value of a color conversion table for converting input image data of the first color system to output image data of the second color system;
A first gradation correction in which gradation correction processing is performed for each color component value of the output value after the density adjustment processing by the density adjustment processing step using a gradation target having a characteristic that the output value with respect to the input value decreases. Processing steps;
A comparison step of comparing a total value of each color component value corrected by the first gradation correction processing step with a limit value.
As a result of the comparison in the comparison step, when the total value of the color component values after the first gradation correction processing is larger than the limit value, the color components are set so that the total value is equal to or less than the limit value. A control process for controlling the value ;
For each color component values that is controlled by said control step, using the input-output characteristic having a characteristic that the output value increases with respect to the input values have a second gradation correction processing step of performing gradation correction processing,
Input-output characteristic having a characteristic that the output value for the input value increases, the image processing method comprising an inverse characteristic der Rukoto of the gradation target. The program for functioning a computer as an image processing apparatus as described in any one of Claims 1 thru | or 15 .

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