JP2008072208A - Image processor, and method thereof, and recording medium thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform preferable color reproduction of an image by performing excellent gray reproduction as to arbitrary paper white and black. <P>SOLUTION: When an achromatic color signal of an input signal is reproduced in color conversion processing for converting an input color signal into an output color signal, target gray reproduction coordinates are determined, a lightness range to be reproduced into a gray target is determined for lightness variation from paper white to black points, and reproduction of gray lines is controlled for other ranges so that chromaticity variation between white points or black points and the gray target may become smooth. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a color correction technique for preferably correcting achromatic color reproduction in an output image in color correction processing when an achromatic signal in a color / monochrome image signal input by an input unit is output by an output unit.

  In recent years, with the spread of digital cameras, the use of digital color images has increased rapidly, and photo print techniques for printing these images satisfactorily have been actively developed.

  In general, printing of achromatic or monochrome images in a color image is realized by image formation using a black color material (ink or toner). However, when an image is formed using only the black color material, the color of the print image is almost determined by the color characteristics of the black color material, and thus it cannot be controlled to preferably reproduce the color of the print image. .

  In addition, achromatic and black and white images in color images are reproduced in black (hereinafter referred to as K), cyan (hereinafter referred to as C), magenta (hereinafter referred to as M), yellow (hereinafter referred to as Y), and other colors. An image may be formed by so-called “composite black” using a material. In this case, by appropriately setting a print color (hereinafter referred to as a gray line) corresponding to the black and white signal values constituting the image, it is possible to control to preferably reproduce the color of the print image.

In recent color ink jet printers, the color reproduction (gray line) of the achromatic color axis is as achromatic as possible in terms of colorimetry with respect to the lightness change from paper white to black, that is, a = b = 0 in the CIELab chromaticity coordinates. Further, in Japanese Patent Laid-Open No. 2001-16475, in order to avoid a change in tone of the gray scale due to the mixed color of CMY ink, the colorimetric value of the gray scale in the formed image is the ab plane of the CIELab space. The gray scale is controlled by controlling the amount of CMYK ink applied so that the hue is in the negative side quadrant of b and the hue angle range of 90 ° and the hue with the black ink is continuously connected. Proposals have been made to minimize fluctuations in hue.
JP 2001-16475 A

  Depending on the paper white color of the print medium, gray reproduction does not necessarily feel that reproduction of a = b = 0 in CIELab chromaticity coordinates is the best, and depending on the color difference between the white point coordinates of the medium and the gray reproduction coordinates, The gray line appears to be tinted depending on the degree of chromaticity change from the white chromaticity point to the gray reproduction coordinate or from the gray reproduction coordinate to the black point with respect to the brightness change, and it is good as color reproduction of the achromatic color axis Is not.

  The present invention has been made to solve the above-described problem. In color conversion processing for converting an input color signal into an output color signal, the present application determines a target reproduction coordinate in gray reproduction, In the brightness change from white to black point, determine the brightness range to be reproduced in the gray target, and for the other range, the chromaticity point change between the white point or black point and gray target will be smooth The purpose is to realize good gray reproduction for any paper white and black by controlling the reproduction of the gray line.

  As a means for solving the above problems and achieving the object, the present invention comprises the following arrangement.

The image processing apparatus of the present invention
In an image processing apparatus having a color conversion processing means for converting an input signal in the input means to an output signal in the output means, when color conversion is performed to an output signal when the input signal is an achromatic signal, the output result by the output means In the achromatic color reproduction, the lightness region between the white point and the black point of the output medium in the output unit is within a predetermined range. In the lightness range setting means for dividing, the achromatic color coordinate setting means for setting the achromatic color chromaticity point coordinates for the predetermined lightness range, and the achromatic color coordinate setting means, the highlight lightness range of the predetermined lightness range and The shape of the locus of the achromatic color coordinates in the shadow lightness range and the intermediate lightness range is set and determined by the achromatic color coordinate setting means A color correction parameter creating means for creating a parameter for performing a color correction process for converting an input signal into an output signal based on the color reproduction; and an output color correction processing means using the created color correction parameter. An image processing apparatus as a feature.

  In the image processing method of the present invention, in an image processing apparatus having color conversion processing means for converting an input signal in an input process into an output signal in an output process, color conversion to an output signal when the input signal is an achromatic signal And a means for performing color correction on the output result of the output means so as to have a predetermined color reproducibility, and in achromatic color reproduction, between the white point and the black point of the output medium in the output means. In the lightness region, the lightness range setting step for dividing the lightness region into the predetermined range, the achromatic color coordinate setting step for setting the achromatic chromaticity point coordinates for the predetermined lightness range, and the achromatic color coordinate setting step, The shape of the locus of the achromatic coordinates in the highlight brightness range and the shadow brightness range of the brightness range and the intermediate brightness range is set. Based on the achromatic color reproduction determined by the means, color correction parameter creating means for creating a parameter for performing color correction processing for converting an input signal into an output signal, and output color correction processing means using the created color correction parameter It is characterized by comprising.

  The image processing recording medium of the present invention performs color conversion to an output signal when the input signal is an achromatic signal in an image processing device having a color conversion processing function for converting an input signal in the input device into an output signal in the output device. In the case of achromatic color reproduction, it has a function of performing color correction so that the output result by the output device has a predetermined color reproducibility. A brightness range setting function for dividing the brightness area into a predetermined range, an achromatic color coordinate setting function for setting achromatic chromaticity point coordinates for the predetermined brightness range, and an achromatic color coordinate setting function. And setting the shape of the locus of achromatic coordinates in the highlight lightness range, shadow lightness range, and intermediate lightness range of the lightness range, Based on the achromatic color reproduction determined by the setting function, a color correction parameter creation function for creating a parameter for color correction processing for converting an input signal into an output signal, and output color correction processing using the created color correction parameter A program for realizing the function is recorded.

  As described above, according to the present invention, the target gray reproduction coordinates are determined in the reproduction of the achromatic signal of the input signal in the color conversion processing for converting the input color signal into the output color signal, and the paper white to black color is determined. In the lightness change to the point, determine the lightness range to be reproduced in the gray target, and for the other range, the gray line so that the white point or the black point and the gray target will change smoothly. By controlling the reproduction of the image, it is possible to realize a color conversion process that realizes a preferable color reproduction of the image image by realizing a good gray reproduction for any paper white and black.

  The outline and configuration of the present invention will be described with reference to the block diagram shown in FIG.

  Reference numeral 101 denotes a CPU, which includes a RAM 103, an operation unit 104, an image according to information data stored in the ROM 102, a control program, an OS (operating system), an application program (hereinafter referred to as an application), a color matching processing module, a device driver, and the like. Various controls of the processing unit 105, the monitor 106, the input device 107, and the output device 108 are performed. Reference numeral 107 denotes an input device, which inputs color space information data for which an arbitrary profile is to be created by an image reading device such as an image scanner including a CCD sensor or a colorimetric device to a host computer. An output device 108 outputs an image by an ink jet printer, a thermal transfer printer, a dot printer, or the like. The RAM 103 is a work area and a temporary save area for various control programs and data input from the operation unit 104. Reference numeral 104 denotes an operation unit that performs setting of the output device setting unit 107 and data input. An image processing unit 105 performs image processing including gray line correction processing and profile creation processing in the present invention.

  Reference numeral 106 denotes a monitor that displays a processing result of the image processing unit 105, data input by the operation unit 104, and the like.

  A main image processing apparatus and its operation for performing gray line reproduction correction processing in creating a profile for converting an input color image signal into an image signal in an output device in the present invention will be described below.

  In the block diagram shown in FIG. 2, in the image processing unit 105, a gray line mapping parameter creation device 201 that performs gray line reproduction correction processing and input information in an arbitrary input color space are mapped to an output color space, and color correction is performed. The configuration of a profile creation device 202 that creates a profile is shown. Each device of the gray line mapping parameter creation device 201 and the profile creation device 202 will be described.

  In the image processing apparatus 105, reference numeral 204 denotes an input color gamut storage device, which stores input color space information that is information relating to the color gamut in the input means such as the monitor 106 and the input device 107. Reference numeral 605 denotes a printer color gamut storage device which stores color gamut information of the printer which is the output device 108.

  Reference numeral 201 denotes a mapping parameter creation device, which refers to the printer color gamut information and the input color space information, and maps the reproduction color of the input color space into the color gamut of the printer in the profile creation device 202. Therefore, a color space compression parameter necessary for the calculation is calculated.

  In the mapping parameter creation device, printer output color information (CMYK data) and input color information (RGB data) are converted into uniform color system color space data represented by the CIELab color space and JCh color space, and the uniform table. Mapping parameters are determined in the color system color space.

  The gray line correction apparatus according to the present invention constitutes a part of the mapping parameter creation apparatus 201. The gray setting information storage device 206 acquires and stores various parameters necessary for gray line setting in the gray line correction process input by the U / I in the operation unit 104 through the terminal 203. Alternatively, various parameters necessary for gray line setting stored in advance in the RAM may be acquired through the terminal 203. The gray correction parameter creation device 207 refers to the printer color gamut information and the input color space information, and based on various parameters necessary for gray line setting stored in the gray setting information storage device 206, the input color For the achromatic signal in the spatial information, a mapping target parameter for determining the mapping target coordinates of the gray line in the CIELab color space so as to achieve a preferable gray reproduction in the printer color gamut is created. The gray correction parameter storage device 208 stores the gray line mapping target parameters created by the gray correction parameter creation device 207.

  In the profile creation device 202, the color gamut mapping device 209 refers to the input color space information in the input color gamut storage device 204, the printer color gamut information in the printer color gamut storage device 205, and the mapping parameter creation device 201. Based on the gray line mapping target parameter stored in the gray correction parameter storage device 208 and the parameter for mapping the input color space so as to achieve a preferable color reproduction within the printer color reproduction range, the input color space signal is converted into the printer. Performs mapping to the color gamut.

  The profile creation device 210 receives a mapping process result in the color gamut mapping device 209 and creates a profile for conversion from input data to printer output element data.

The created profile is stored in the profile storage device 211.
On the other hand, 212 is a terminal, and the stored profile is transferred to the output device through the terminal 212, and the output device outputs an output image that has been subjected to color correction processing by the profile.

  The operation of the profile creation device 202 in the above configuration will be described. In the mapping operation of the profile creation device 202 in this embodiment, the L * a * b * color space is used as the uniform color system. First, in response to a command from the CPU 101, the color gamut information of the input color space and the color gamut information of the printer are transmitted. The transmitted two color gamut information is stored in the input color space gamut storage device 204 and the printer gamut storage device 205 in the image processing apparatus 105, respectively. Is remembered as

  Next, the inside of the profile creation device 202 operates as follows. First, the mapping parameter creation device 201 operates, and the gamut mapping device 209 calculates various parameters necessary for color space compression.

  At this time, gray line mapping parameters in the present invention are also created.

  When the parameter calculation is completed, the color gamut mapping device 209 operates to map the color gamut of the input color space to the printer color reproduction gamut in the uniform color system. Next, the profile creation device 210 creates a profile for conversion from the input information to the printer color information with reference to the mapping color reproduction area as the final mapping result, and writes the profile in the profile storage device 211. This completes a series of operations.

  Next, the gray line correction processing in the present invention will be described in detail.

  FIG. 3 shows a block configuration in the gray correction parameter creation device 207.

First, the gradation characteristic conversion unit 307 outputs the achromatic signal GL in the input signal and the achromatic signal GL based on the gradation characteristic of the gray line in the input color space stored in the input gray characteristic storage unit 308. It is converted into the lightness L ^{* of the} print image obtained when output by the device 108.

The processing in the gradation characteristic conversion unit 307 is performed because the achromatic signal GL in the input signal is determined based on the characteristics of the device (digital camera, scanner, etc.) that generated the input image and preferable gradation characteristics. This is because the reproduction brightness in the color space is different from the reproduction of the brightness L ^* of the printed image obtained when output by the output device 108.

FIG. 5 is a memory configuration diagram illustrating an example of a gray reproduction setting storage unit 309 that stores the gray line gradation characteristics in the input color space, converted by the gradation characteristic conversion unit 307. The gray characteristic memories 502 to 506 stored in the black and white signal storage memory 501 store correspondence lightness L ^{* of the} print image obtained when the output device 1008 outputs the discrete black and white signal GL as gradation characteristic data. And is related to the brightness of the printed image. The lightness L ^* corresponding to an arbitrary black and white signal GL can be obtained by a known interpolation calculation.

In FIG. 5, the monochrome signal GL stored in the monochrome signal storage memory 501 is an 8-bit signal value, and the lightness L ^* (Lmax) corresponding to GL = 255 is the output device 1008 and the image recording medium (printing paper, etc.). The brightness L ^* (Lmin) corresponding to GL = 0 is the minimum brightness reproducible by the output device 1008 and the image recording medium (printing paper or the like). Typically, Lmax is the lightness L ^* of the color of the image recording medium (printing paper or the like) (hereinafter referred to as white printing color).

In this embodiment, in the gray characteristic memories 502 to 506 stored in the black and white signal storage memory 501 in the gray reproduction setting storage unit 309, the gradation characteristic conversion unit 307 is used as reproduction gradation characteristic data of the gray line in the image processing apparatus. By defining the gray reproduction chromaticity point coordinates (a ^* , b ^* ) for the lightness L ^{* of the} printed image obtained when output by the output device 1008 regarding the discrete black and white signal GL converted by Determine the reproduction of the line.

  Here, with reference to FIG. 7, the reproduction and setting method of the gray line in the image processing apparatus 1005 will be described in detail.

FIG. 7 is a diagram schematically showing the locus of the gray line in the first embodiment projected on the a ^* b ^* plane of the CIELAB color space. In FIG. 7, a white point W701 is a chromaticity point of a print color corresponding to the maximum value (white signal) of the monochrome signal GL, and a black point K707 is a print color corresponding to the minimum value (black signal) of the monochrome signal GL. It is a chromaticity point. Typically, the point W701. Is the chromaticity point of the white printing color, and the point K707 is the minimum lightness color (hereinafter, black printing color) that can be reproduced by the image output apparatus 102 and the image recording medium (printing paper or the like). ) Chromaticity point. Point G704 is a preferred gray chromaticity point. In the first embodiment, as shown in FIG. 7, the image signal is processed so that the gray line from the white point W701 to the black point K707 passes through a chromaticity point (point G704) preferable for achromatic color reproduction on the output medium. By doing so, it is possible to obtain a printed image with a good color.

Here, a preferable gray chromaticity point is located on the b ^* minus side, for example, in the vicinity of the b ^* axis.

Next, in FIG. 8, the locus of the gray line from the white point W701 (801) to the black point K707 (811) shown in FIG. 7 is converted into coordinates with the horizontal axis a ^* and the vertical axis L ^* . It is a figure which shows a result.

  In FIG. 8, lightness Lw812 indicates the lightness of reproduction at the point W801, the lightness of the print color corresponding to the maximum value (white signal) of the black and white signal GL, lightness Lk815 indicates the lightness of reproduction at the point K811, and black and white signal This is the lightness of the print color corresponding to the minimum value of GL (black signal). Typically, the lightness Lw812 is the lightness of the white print color, and the lightness Lk815 is the minimum lightness color (hereinafter referred to as black print color) that can be reproduced by the image output device 102 and the image recording medium (printing paper or the like). .

  In this embodiment, first, in order to realize the preferable gray reproduction, the brightness area is divided.

  The lightness division is set by determining Lgu813 and Lgl1814 indicating the boundary lightness of the lightness region, and the lightness range (Lw812-Lgu813) set as the highlight portion and the lightness range (Lgl1814-Lk815) set as the shadow portion ), An area between the highlight part and the shadow part is set as an intermediate brightness part (Lgu813-Lgl1814).

  The condition for dividing each lightness range is to set the chromaticity point of the intermediate lightness part to the common preferred chromaticity point, and the highlight / shadow parts are reproduced in the middle of the white point, black point and preferred gray respectively. A point is set.

  And, as shown in the gray reproduction points 804 to 808, by processing the image signal so that the chromaticity point of the intermediate lightness portion is a preferable gray chromaticity point, the reproduction of the gray line is output with a preferable color. Is possible.

  Further, with reference to FIG. 7 and FIG. 8, a mechanism for suppressing a color change in the highlight and shadow portions will be described. In FIG. 8, when the lightness range of the above intermediate lightness portion is wide, that is, when Lgu813-Lgl1814 is large, most of the input monochrome signals excluding the highlight portion (Lw812-Lgu813) and the shadow portion (Lgl1814-Lk815) Reproduced at a preferred chromaticity point. However, in this case, since the change rate of the chromaticity point related to lightness is large in the highlight portion near the white print color and the shadow portion near the black print color, depending on the chromaticity coordinate change in the highlight portion and the shadow portion, the gradation A color change may be observed in an image or the like.

For example, the gray reproduction point 803/802 at a certain lightness in the highlight portion in FIG. 8 is the gray reproduction point 703 (803) in which the gray reproduction point in FIG. 7 is set on a straight line connecting the white point W701 and the gray point G704. And the gray reproduction point 702 (802) set on a curve connecting the white point W701 and the gray point G704, and comparing the gray point 703 and the gray point 702, the distance of the gray reproduction point 704 Since the change amount in the a ^* axis direction is smaller and the change in the b ^* axis direction is a change in the bluish direction for gray, it is possible to reduce the change in the color with the gray point G704. Therefore, it can be said that it is more preferable gray reproduction when the gray reproduction point at a certain lightness in the highlight portion is set to the gray reproduction point 702 than the gray reproduction point 703. In FIG. 8, the gray reproduction point 809/810 at a certain brightness in the shadow portion also includes a gray reproduction point 705 (809) set on a straight line connecting the black point K707 and the gray point G704, a black point K707, and a gray point G704. The same can be said for the gray reproduction point 706 (810) set on a certain curve to be connected.

  In view of this, the image processing apparatus 105 limits the change tendency of the chromaticity point by suppressing the change in the chromaticity point by appropriately changing the change of the chromaticity point coordinates in the highlight portion and the shadow portion shown in FIG. .

For changes in chromaticity points in the highlight and shadow areas, refer to the table data that describes the coordinate values for the discrete brightness values in the highlight and shadow areas for the coordinate values that felt the least change in color. Model formula that calculates a coordinate value that reduces the change in color by weighting the a ^* b ^* coordinate change amount as described above using the brightness value, paper white, and black point coordinates as input May be the result obtained by

  Next, details of the gray correction parameter creation processing by the gray correction parameter creation device 207 will be described.

  FIG. 6 is a diagram illustrating an example of a gray line setting table 601 stored in the gray setting data storage unit 301. In FIG. 6, the type of output medium (media A, medium B) in the output device is defined as a gray design parameter creation condition, and the intermediate lightness range (gray center of gravity lightness range) and gray reproduction value in the intermediate lightness range for each medium. (Gray centroid value), gray design data in the highlight portion, and gray design data in the shadow portion are described.

  Here, the brightness value used in each setting of the reproduction coordinate value of the gray line described below is a value defined as the absolute value brightness with respect to the absolute value of the paper white spot brightness and the black spot brightness of the output medium, Alternatively, any of the values defined as the brightness values normalized using the absolute values of the paper white spot brightness and the black spot brightness of the output medium may be used, and the brightness coordinates finally stored in the monochrome signal storage memory 501 In order to describe the absolute value brightness, when the normalized brightness is used in the design of the gray line, the absolute brightness value may be described with reference to the paper white point brightness and black point brightness of the output medium.

As an example of table data definition, in the gray line setting table 611, first, the intermediate brightness range (gray center of gravity brightness range) for dividing the brightness area is defined as the boundary brightness upper limit L1 and the boundary brightness lower limit L2 of the brightness range. Stored in the memory 604. Next, the common gray reproduction coordinates in the intermediate lightness range (gray centroid lightness range) are stored in the memory 603 as chromaticity coordinate values a ^* and b ^* (a1, b1) as gray centroid value data. Yes.

Regarding the change in coordinates of the gray locus in the highlight portion (media white lightness to L1), the correspondence between the lightness signal L and the chromaticity coordinate values a ^* and b ^* in the gray line locus shown in FIG. (A3, b3), (a4, b4), (a5, b5) are defined and stored in the memory 605 as correspondence tables extracted with respect to the signal L (L3, L4, L5). Regarding the change in the coordinates of the gray locus in the shadow portion (media black lightness to L2), the correspondence between the lightness signal L and the chromaticity coordinates a * and b * in the gray line locus shown in FIG. They are defined as correspondence tables extracted for L (L6, L7, L8), and (a6, b6), (a7, b7), (a8, b8) are defined and stored in the memory 606, respectively. The chromaticity coordinate signals (a ^* , b ^* ) corresponding to an arbitrary lightness signal L can be obtained from this gray line setting table by a known interpolation calculation.

  As an example of the table data definition content, in the gray line setting table 612, a model formula for calculating the brightness or coordinate value in the three-dimensional space is set as the definition of each item, and the value obtained by the model formula is set as the gray design value. Used as

  First, an intermediate brightness range (gray gravity center brightness range) for dividing the brightness region is defined as an equation Fc (m) for obtaining the boundary brightness upper limit L9 and the boundary brightness lower limit L10 of the brightness range, and is stored in the memory 604. m represents a parameter necessary for determining the brightness range based on information on the output medium. Next, for the gray barycentric value data, which is a common gray reproduction coordinate in the intermediate lightness range (gray barycentric lightness range), an equation Fg (m) for obtaining chromaticity coordinates (a9, b10) is stored in the memory 603. . m is a parameter necessary for determining the gray barycentric value based on the information on the output medium, and includes at least information on the paper white color, black point, color reproduction range, etc. in the output medium.

  For the change in coordinates of the gray locus in the highlight area (media white brightness ~ L1), the coordinates on the gray locus as shown in Fig. 7 are output in the highlight design memory 610 for the brightness input in the highlight area. The following formula 1 is stored.

(a, b) = F1 (L) (Formula 1)
Regarding the change in the coordinates of the gray locus in the shadow portion (media black brightness to L2), the following formula is used to output the coordinates of the gray locus as shown in FIG. 7 in the shadow design memory 611 for the lightness input in the shadow portion. 2 is stored.

(a, b) = F2 (L) (Formula 2)
In this embodiment, the description method regarding the change in chromaticity point in the highlight part and the shadow part may be table data or a model formula depending on the type of output medium, as shown in FIG. It is determined appropriately depending on the type of output medium selected.

  FIG. 3 shows a configuration of the gray correction parameter creation device 207 in the mapping parameter creation device 201 in the image processing unit 105.

  In the image processing device 105, the gray setting information storage device 206 stores data related to the gray setting parameters in the format shown in FIG. 6 as described above, and is referred to according to the type of output device or the type of output medium. The gray line setting table is acquired and stored in the gray setting data storage unit 301.

  In the gray correction parameter creation device 207, based on the gray setting parameters stored in the gray setting data storage unit 301, the lightness region division processing is performed for the first preferable gray reproduction.

  The gray brightness range setting unit 302 determines the brightness range in the output medium based on the brightness range design parameter on the chromaticity line table stored in the gray setting data storage unit 301.

The gray centroid setting unit 303 determines the gray reproduction chromaticity point in the gray centroid lightness range in the output medium based on the gray centroid coordinate design parameter on the chromaticity line table stored in the gray setting data storage unit 301, and The brightness of the printed image obtained when the output device 1008 outputs the discrete monochrome signal GL corresponding to the intermediate brightness range in the gray characteristic memories 502 to 506 stored in the monochrome signal storage memory 501 in the gray reproduction setting storage unit 309 L * is converted into chromaticity coordinate signals (a ^* , b ^* ) in the CIELAB color space, which is a gray coordinate.

The highlight gray setting unit 304 is based on the highlight gray design parameters on the chromaticity line table stored in the gray setting data storage unit 301, and the gray characteristics stored in the monochrome signal storage memory 501 in the gray reproduction setting storage unit 309 With respect to the lightness L * of the printed image obtained when the output device 108 outputs the discrete black and white signal GL corresponding to the highlight portion lightness range in the memories 502 to 506, the input signal at the highlight portion of the output medium Conversion processing is performed on the chromaticity coordinate signals (a ^* , b ^* ) in the CIELAB color space, which are gray coordinates for a certain lightness signal L.

Based on the shadow part design parameters on the chromaticity line table stored in the gray setting data storage unit 301, the shadow setting unit 305 is based on the gray characteristic memories 502 to 502 stored in the monochrome signal storage memory 501 in the gray reproduction setting storage unit 309. With respect to the lightness L ^{* of the} print image obtained when the output device 108 outputs the discrete black and white signal GL corresponding to the shadow portion lightness range in 506, the lightness signal L that is an input signal in the shadow portion of the output medium Conversion processing is performed on the chromaticity coordinate signals (a ^* , b ^* ) of the CIELAB color space, which are gray coordinates.

  The gray correction parameter calculation unit 306 generates a gray generation parameter for the final color reproduction of the gray line in the color gamut mapping device 209.

  The created gray mapping parameter is stored in the gray correction parameter storage device 208.

  The color gamut mapping device 209 uses the gray mapping parameter created in the present embodiment for the output color with respect to the input signal, for the achromatic signal in the input signal, and for other colored signals, the pseudo contour for the gray mapping result, etc. A mapping process for creating a color correction profile in the entire color space is performed so as not to cause problems with the tone characteristics and color reproduction, and the profile creation apparatus 210 creates a color correction profile.

  The created color correction profile is stored in the profile storage device 211.

  The operation of the image processing apparatus having the above configuration will be described with reference to the flowchart shown in FIG.

  First, in step 401, input color space color gamut information and printer color gamut information are acquired from the input color gamut storage device 204 and the printer color gamut storage device 205 in the profile creation device 202, respectively.

  In step 402, an output medium in the output device for creating the color correction profile is selected, and gray design data corresponding to the medium type stored in the gray setting information storage device 206 is acquired by the gray correction parameter creation device 207. .

  In step 403, the brightness range of the highlight portion is determined based on the gray design data acquired in step 402, and the gray reproduction chromaticity point for the input signal value in the highlight portion is determined.

  In step 404, based on the gray design data acquired in step 402, the brightness range of the shadow portion is determined, and the gray reproduction chromaticity point for the input signal value in the shadow portion is determined.

  In step 405, the gray centroid value reproduction brightness range is determined based on the gray design data acquired in step 402, and the gray reproduction chromaticity point for the input signal value in the gray centroid value reproduction brightness range is determined.

  In step 406, gray correction parameters used in the color gamut mapping device 209 are created from the gray reproduction chromaticity point data corresponding to the input signal values determined in steps 403 to 405.

  In step 407, the gray correction parameter created in step 406 is stored in the gray correction parameter storage device 208.

  In step 408, the color gamut mapping device 209 obtains an input signal from the input color gamut storage device 204, and based on the gray mapping parameters calculated in step 906 for the printer color gamut in the printer color gamut storage device 205, the gray line In addition, the input signal is acquired for other colors, the mapping process to the printer color gamut in the printer color gamut storage device 205 is performed, and a color correction profile is created based on the mapping result.

  In step 409, the created color correction profile is stored in the profile storage device 211.

  According to this embodiment, a color correction profile is created by color correction processing for preferably reproducing the achromatic signal in the input image as gray line reproduction of the output image in the output device, and the created color correction profile is A preferable color reproduction is realized for the output image by the image processing apparatus that performs the used image processing.

(Other Example 2)
For the preferred gray reproduction in the image processing apparatus, in the present embodiment, in order to realize the gray reproduction more accurately, the gray chromaticity point reproduction target range is set for the coordinates of the mapping destination of the gray chromaticity point, It is characterized by setting a gray reproduction point.

FIG. 10 is a diagram schematically showing the locus of the gray line in the second embodiment projected on the a ^* b ^* plane of the CIELAB color space. In FIG. 10, a point W1001 is the chromaticity point of the printing color corresponding to the maximum value (white signal) of the monochrome signal GL, and a point K1007 is the chromaticity of the printing color corresponding to the minimum value (black signal) of the monochrome signal GL. Is a point. Typically, the point W1001 is the chromaticity point of the white print color, and the point K1007 is the minimum lightness color that can be reproduced by the image output apparatus 102 and the image recording medium (printing paper or the like) (hereinafter referred to as black print color). This is the chromaticity point. Point G1004 is a preferred gray chromaticity point. In the first embodiment, as shown in FIG. 10, by processing the image signal so that the gray line from the white point W1001 to the black point K1007 passes through the preferred chromaticity point (point G1004), a good color tone is obtained. It is possible to obtain a print image.

Here, preferred chromaticity point of gray, for example, b ^* in the axial vicinity, b ^* is located on the minus side.

Next, FIG. 11 is a diagram showing a result of converting the locus of the gray line shown in FIG. 10 into coordinates with the horizontal axis a ^* and the vertical axis L ^* .

  In FIG. 11, the lightness Lw1112 indicates the lightness of reproduction at the point W1101, and is the lightness of the print color corresponding to the maximum value (white signal) of the black and white signal GL. The lightness Lk1115 indicates the lightness of reproduction at the point K1111. This is the lightness of the print color corresponding to the minimum value of GL (black signal). Typically, the lightness Lw1112 is the lightness of the white print color, and the lightness Lk1115 is the minimum lightness color (hereinafter referred to as black print color) that can be reproduced by the image output device 102 and the image recording medium (printing paper or the like). .

  In the present embodiment, for the first preferable gray reproduction, the brightness area is divided as in the first embodiment.

Brightness range set as highlight part (Lw1112-Lgu1113),
Brightness range (Lgl11114-Lk1115) set as the shadow part,
An area sandwiched between the highlight part and the shadow part is set as an intermediate brightness part (Lgu1113-Lgl11114).

  The condition for dividing each lightness range is to set the chromaticity point of the intermediate lightness part to the common preferred chromaticity point, and the highlight / shadow parts are reproduced in the middle of the white point, black point and preferred gray respectively. A point is set.

  Then, by processing the image signal so that the chromaticity point of the intermediate lightness portion is a preferable gray chromaticity point, it is possible to output the reproduction of the gray line with a preferable color.

  Further, with reference to FIG. 10 and FIG. 11, a mechanism for suppressing color change in the highlight portion and the shadow portion will be described. In FIG. 11, when the lightness range of the above intermediate lightness portion is wide, that is, when Lgu1113-Lgl11114 is large, most of the input monochrome signals excluding the highlight portion (Lw1112-Lgu1113) and the shadow portion (Lgl11114-Lk1115) Reproduced at a preferred chromaticity point. However, in this case, since the change rate of the chromaticity point related to lightness is large in the highlight portion near the white print color and the shadow portion near the black print color, depending on the chromaticity coordinate change in the highlight portion and the shadow portion, the gradation A color change may be observed in an image or the like.

  Therefore, in this embodiment, as shown in FIG. 10, for the gray reproduction in the highlight part shadow part, a range 1108 to be reproduced in order to obtain a preferable gray is set in advance, and the gray mapping point is determined within the range. It is characterized by performing. The gray reproduction range data is a parameter designated by the user and is stored in the storage device. Further, the gray reproduction range data may be a value set for each medium, or may be region information calculated by a model formula using information such as paper white selected by the output medium as a parameter. good.

  Further, it may be a range set individually for the gray reproduction brightness in the highlight portion and the shadow portion. In this case, it is assumed that a gray reproduction range target corresponding to the gray reproduction brightness is appropriately selected and used for setting a gray line.

  For example, the gray reproduction point 1103/1102 at a certain lightness in the highlight portion in FIG. 11 is the gray reproduction point 1003 (1103) in which the gray reproduction point in FIG. 10 is set on a straight line connecting the white point W1001 and the gray point G1004. And the gray reproduction point 1002 (1102) set on a curve connecting the white point W1001 and the gray point G1004.

  A preferable gray reproduction range in this embodiment is an elliptical region 1008 that is commonly applied to all gray reproduction brightness values on the ab coordinate in FIG. 10, and in FIG. 11, on the a axis that is the horizontal axis. In FIG. 2, the region is defined by the boundary lines 1116 and 1117. A preferable gray range is an area describing a gray reproduction range that is determined to be preferable in consideration of color change from the gray barycentric point.

  Accordingly, in FIG. 10, the gray reproduction point 1003 in the highlight portion is set between the previous white coordinate point and the next gray centroid point in the data coordinate position change. Is set to the coordinates on the boundary of the reproduction target range that minimizes the amount of change. Thereby, it is possible to set the highlight gray in consideration of the color change from the white point and the color change from the gray barycentric point. In Fig. 10, the gray reproduction point 1005/1006 at a certain brightness in the shadow area is also referred to the black point K1007, the gray point G1004, and the gray reproduction range 1008, and the gray reproduction point 1006 (810) set within the gray reproduction range. The same can be said.

  The operation of the image processing apparatus having the above configuration will be described with reference to the flowchart shown in FIG.

  First, in step 901, input color space color gamut information and printer color gamut information are acquired from the input color gamut storage device 204 and the printer color gamut storage device 205 in the profile creation device 202, respectively.

  In step 902, an output medium in the output device for creating the color correction profile is selected, and gray design data corresponding to the medium type stored in the gray setting information storage device 206 is acquired by the gray correction parameter creation device 207, A gray line reproduction target range in the gray design data is acquired.

  In step 903, the brightness range of the highlight portion is determined based on the gray design data acquired in step 902, and the gray reproduction chromaticity point for the input signal value in the highlight portion refers to the gray line reproduction target range. Determined.

  In step 904, the brightness range of the shadow portion is determined based on the gray design data acquired in step 902, and the gray reproduction chromaticity point for the input signal value in the shadow portion is determined with reference to the gray line reproduction target range. Is done.

  In step 905, the gray centroid value reproduction brightness range is determined based on the gray design data acquired in step 902, and the gray reproduction chromaticity point for the input signal value in the gray centroid value reproduction brightness range is determined.

  In Step 906, the gray reproduction chromaticity point coordinates determined in Steps 903 to 905 are compared with the gray line reproduction target range. If the coordinates are out of the range, the process returns to Step 903 and subsequent steps to re-examine the coordinate points outside the range. Set up.

  In step 906, the gray reproduction chromaticity point coordinates determined in steps 903 to 905 are compared with the gray line reproduction target range, and if within the range, the processing from step 907 is performed.

  In step 907, a gray correction parameter used in the color gamut mapping device 209. is created from the gray reproduction chromaticity point data corresponding to the input signal value determined in steps 903 to 906.

  In step 908, the gray correction parameter created in step 907 is stored in the gray correction parameter storage device 208.

  In step 909, the gamut mapping device 209 obtains an input signal from the input gamut storage device 204, and based on the gray mapping parameters calculated in step 907 for the printer color gamut in the printer gamut storage device 205, the gray line In addition, the input signal is acquired for other colors, the mapping process to the printer color gamut in the printer color gamut storage device 205 is performed, and a color correction profile is created based on the mapping result.

  In step 910, the created color correction profile is stored in the profile storage device 211.

  According to this embodiment, a color correction profile is created by color correction processing for preferably reproducing the achromatic signal in the input image as gray line reproduction of the output image in the output device, and the created color correction profile is A preferable color reproduction is realized for the output image by the image processing apparatus that performs the used image processing.

(Other Example 3)
12, 13, 14, and 15 show U / I configurations in the image processing apparatus.

  The present embodiment is an operation unit U / I for realizing the first and second embodiments in the image processing apparatus 105.

  In FIG. 12, U / I 1201 is a data input U / I for acquiring data necessary for the gray line design in this embodiment.

  Input color space data in input color gamut data setting unit 1202, output color space data in output color gamut data setting unit 1203, data storing gray design target on output medium in output device in color correction data setting unit 1204, color correction The profile output setting unit 1205 specifies the output file name of the color correction profile.

  With reference buttons 1206, 1207, 1208, and 1209, the storage location of each data input to the image processing apparatus can be referred to and a file can be designated.

  Next, as shown in FIG. 13, in the gray line condition setting U / I 1301, the list button 1304 of the output device setting unit 1302 is pressed to specify an output device on the list, and the list button 1305 of the output medium setting unit 1303. Press to specify the output medium on the list. By pressing an OK button 1306 for gray correction parameter setting, a gray correction parameter corresponding to the designated output device / output medium is set.

  As shown in FIG. 14, in the gray correction U / I 1401, the gray setting display LC screen 1402 displays an input color space shape 1410, an output color space shape 1411, and a gray line set point 1412. In the gray line setting unit 1407, the reproduction brightness and coordinate values at each mapping point can also be set by the user.

  As for the brightness range setting, the boundary brightness value for the highlight part and the intermediate brightness part in the highlight part boundary brightness setting part 1403, and the initial boundary brightness value for the shadow part and the intermediate brightness part in the shadow part boundary brightness setting part 1404 The value is displayed, and the mapping result is displayed on the gray line of the gray setting display LC screen.

  By pressing the reset button 1405, the setting of the highlight portion boundary brightness setting unit 1403 can be reset to the initial value.

  By pressing a reset button 1406, the setting of the shadow portion boundary brightness setting unit 1404 can be reset to the initial value.

  When the user inputs a value in the highlight part boundary lightness setting unit 1403 and the shadow part boundary lightness setting unit 1404, the gray line mapping result on the gray setting display LC screen 1402 is changed and displayed again.

  Lightness boundary lines 1415 and 1416 indicate setting values in the highlight portion boundary lightness setting unit 1403 and the shadow portion boundary lightness setting unit 1404. As for the brightness boundary lines 1415 and 1416, when the user inputs values in the highlight part boundary brightness setting part 1403 and the shadow part boundary brightness setting part 1404, the positions of the brightness boundary lines 1415 and 1416 on the gray setting display LC screen 1402 are changed. And redisplayed.

  In the gray line setting unit 1407, the mapping brightness and mapping coordinates of the gray point 1412 used for mapping the gray line are set. The user can change the setting value of the lightness L coordinate ab with respect to the gray point on the gray line setting unit.

  As shown in FIG. 15, on the gray setting display LC screen 1402 and the gray setting display coordinate screen 1502 on the gray correction U / I 1501, gray reproduction target ranges 1413, 1414, and 1509 in the second embodiment are also displayed, and mapping set points are displayed. When the gray reproduction target ranges 1413, 1414, and 1509 are not included, the gray line setting unit 1407 has a function (1409) that advises the user, for example, that the display color changes as an attention part.

  Further, by pressing a reset button 1408, the setting of the gray line setting unit can be reset to the initial value.

  In the gray correction U / I 1501, a test image setting unit 1503 and a test print button 1505 are used to create a color correction profile prototype in the image processing apparatus 105 using the gray line set in the gray line setting unit 1407. The test image designated by the test image setting unit 1503 is output, and the user can confirm by performing image reproduction output using an actual gray line. A reference button 1504 can be used to refer to the storage location of the image data input to the test image setting unit 1503 and specify a file.

  Finally, the profile creation button 1506 causes the image processing apparatus 105 to perform mapping processing from the input color space to the output color space based on the gray line design set by the user using the U / I according to the present embodiment. A color correction profile having the file storage location and file name shown in the color correction profile name display unit 1507 is created.

  According to this embodiment, a color correction profile is created and created by U / I for color correction processing for preferably reproducing the achromatic signal in the input image as gray line reproduction of the output image in the output device. A preferable color reproduction is realized for the output image by the image processing apparatus that performs image processing using the color correction profile.

(Other Example 4)
<Storage medium>
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer), and a device (for example, a copying machine and a facsimile device) including a single device. You may apply to.

  Another object of the present invention is to supply a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium. Needless to say, this can also be achieved by reading and executing the program code stored in.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  As a storage medium for supplying the program code, for example, a flexible disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, or the like can be used.

  In addition, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) running on the computer based on the instruction of the program code. It goes without saying that a part of the actual processing is performed and the functions of the above-described embodiments are realized by the processing.

  Further, after the program code read from the storage medium is written to a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board 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 block diagram illustrating a schematic configuration of an image processing apparatus commonly used in an embodiment. It is a block diagram which shows the structure of an image processing apparatus. It is a block diagram which shows the structure of an image processing apparatus. It is a flowchart which shows the flow of a process. It is a block diagram which shows the memory structure of an image processing apparatus. It is a block diagram which shows the memory structure of an image processing apparatus. It is a figure which shows the gray line to be set. It is a figure which shows the gray line to be set. It is a flowchart which shows the flow of a process. It is a figure which shows the gray line to be set. It is a figure which shows the gray line to be set. It is a figure which shows the U / I structure in an image processing apparatus. It is a figure which shows the U / I structure in an image processing apparatus. It is a figure which shows the U / I structure in an image processing apparatus. It is a figure which shows the U / I structure in an image processing apparatus.

Claims (12)

  In an image processing apparatus having a color conversion processing means for converting an input signal in the input means to an output signal in the output means, when color conversion is performed to an output signal when the input signal is an achromatic signal, the output result by the output means In the achromatic color reproduction, the lightness region between the white point and the black point of the output medium in the output unit is within a predetermined range. In the lightness range setting means for dividing, the achromatic color coordinate setting means for setting the achromatic color chromaticity point coordinates for the predetermined lightness range, and the achromatic color coordinate setting means, the highlight lightness range of the predetermined lightness range and The shape of the locus of the achromatic color coordinates in the shadow lightness range and the intermediate lightness range is set and determined by the achromatic color coordinate setting means A color correction parameter creating means for creating a parameter for performing a color correction process for converting an input signal into an output signal based on the color reproduction; and an output color correction processing means using the created color correction parameter. An image processing apparatus as a feature.   In an image processing apparatus having a color conversion processing means for converting an input signal in the input means to an output signal in the output means, when color conversion is performed to an output signal when the input signal is an achromatic signal, the output result by the output means In the achromatic color reproduction, the lightness region between the white point and the black point of the output medium in the output unit is within a predetermined range. In the lightness range setting means for dividing, the achromatic color coordinate setting means for setting the achromatic color chromaticity point coordinates for the predetermined lightness range, and the achromatic color coordinate setting means, the highlight lightness range of the predetermined lightness range and It is characterized by setting the shape of the locus of achromatic coordinates in the shadow lightness range and the intermediate lightness range, and also highlight lightness range and shadow Achromatic color condition setting means for setting conditions for the chromaticity point coordinates on the locus with respect to the shape of the locus of the achromatic color coordinates in the lightness range, and the highlight lightness range and the shadow lightness within the range defined by the achromatic color condition setting means Achromatic color correcting means for correcting a locus of achromatic color coordinates in a range, and color correction processing for converting an input signal into an output signal based on the achromatic color reproduction determined by the achromatic color coordinate setting means and the achromatic color correcting means An image processing apparatus comprising: a color correction parameter creating means for creating a parameter for performing an output; and an output color correction processing means using the created color correction parameter.   The shape of the achromatic color coordinate locus in the highlight lightness range and the shadow lightness range in the achromatic color coordinate setting means is nonlinear on the chromaticity point coordinates, and is controlled by the lightness. The image processing apparatus according to claim 2.   The shape of the achromatic color locus in the highlight lightness range and the shadow lightness range in the achromatic color coordinate setting means is non-linear on the chromaticity point coordinates, and is controlled by the movement distance on the lightness and chromaticity point locus. The image processing apparatus according to claim 1 or 2, wherein   3. The image processing apparatus according to claim 1, wherein the achromatic color coordinate in the intermediate lightness range in the achromatic color coordinate setting unit is a preferable gray chromaticity point.   The preferred gray chromaticity point coordinates of the achromatic color coordinates in the intermediate lightness range in the achromatic color coordinate setting means are set for each media type and can be selected according to the media type. An image processing apparatus according to 1.   3. The image processing according to claim 1, wherein a preferred gray chromaticity point coordinate of the achromatic color coordinate in the intermediate lightness range in the achromatic color coordinate setting means is common in the intermediate lightness range. apparatus.   In the achromatic color condition setting means for setting a condition for the chromaticity point coordinates on the locus with respect to the shape of the locus of the achromatic color coordinates in the highlight lightness range and the shadow lightness range, the condition is for each lightness range, The image processing apparatus according to claim 2, wherein different condition ranges are set.   The lightness and lightness range defined in the achromatic color coordinate setting means are absolute lightness values or lightness coordinates normalized by paper white lightness and black point lightness in the output medium, and The image processing apparatus according to claim 2.   In an image processing apparatus having a color conversion processing means for converting an input signal in the input means into an output signal in the output means, means for displaying a color reproduction result obtained by color conversion to an output signal when the input signal is an achromatic color signal; Means for displaying the result of color correction so that the output result by the output means has a predetermined color reproducibility, and in achromatic color reproduction, from the white point of the output medium in the output means Means for setting and displaying a lightness range to be divided into a predetermined range for a lightness region between black points, means for setting and displaying achromatic chromaticity point coordinates for the predetermined lightness range, and the achromatic color coordinate setting display means Set and display the shape of the locus of achromatic coordinates in the highlight lightness range and shadow lightness range of the predetermined lightness range and the intermediate lightness range. And a means for determining and displaying a parameter for performing color correction processing for converting an input signal into an output signal based on the achromatic color reproduction determined by the achromatic color coordinate setting display means. An image processing apparatus.   In an image processing apparatus having a color conversion processing step for converting an input signal in an input step into an output signal in an output step, when color conversion is performed to an output signal when the input signal is an achromatic signal, the output result of the output step In the achromatic color reproduction, the lightness region between the white point and the black point of the output medium in the output step is within a predetermined range. In the brightness range setting step for dividing, the achromatic color coordinate setting step for setting achromatic chromaticity point coordinates for the predetermined brightness range, and the achromatic color coordinate setting step, the highlight brightness range of the predetermined brightness range and The shape of the locus of the achromatic color coordinates in the shadow lightness range and the intermediate lightness range is set, and is determined by the achromatic color coordinate setting step A color correction parameter creating step for creating a parameter for performing a color correction process for converting an input signal into an output signal based on chromatic reproduction, and an output color correction process step using the created color correction parameter. A characteristic image processing method.   In an image processing apparatus having a color conversion processing function for converting an input signal in an input apparatus into an output signal in an output apparatus, when color conversion is performed to an output signal when the input signal is an achromatic signal, the output result from the output apparatus In the achromatic color reproduction, the lightness region between the white point and the black point of the output medium in the output device is within a predetermined range. In the brightness range setting function to be divided, the achromatic color coordinate setting function for setting the achromatic color chromaticity point coordinates for the predetermined brightness range, and the achromatic color coordinate setting function, the highlight brightness range of the predetermined brightness range and The shape of the locus of the achromatic color coordinates in the shadow lightness range and the intermediate lightness range is set, and is determined by the achromatic color coordinate setting function. A program for realizing a color correction parameter creation function for creating a parameter for performing color correction processing for converting an input signal into an output signal based on color reproduction, and an output color correction processing function using the created color correction parameter A recording medium for recording.

Images