JP6136740B2 - Color conversion profile generation device, color conversion profile generation program, and color conversion device - Google Patents

Description

  The present invention relates to a color conversion profile generation device, a color conversion profile generation program, and a color conversion device.

  In Patent Document 1, in a color conversion profile generating apparatus that ejects ink droplets onto a recording sheet and forms an image corresponding to an input image on the recording sheet, a determination unit that determines the type of the recording sheet; A recording unit that records an image on the recording sheet by ejecting ink droplets; a determination unit that determines at least one of the chromaticity, density distribution, and image type of the input image; and a recording sheet that is determined by the determination unit. And a suppression unit that suppresses bleeding between ink droplets caused by flow diffusion of ink droplets ejected onto the recording paper by the recording unit based on a type and a determination result by the determination unit. A conversion profile generation device is disclosed.

  In Patent Document 2, multi-valued image data in which one pixel consists of n bits is output image data for recording with a color color conversion profile generation device capable of expressing gradation by overlapping ink droplets. In the color image processing device for conversion, an area discriminating means for discriminating a predetermined area in the multi-valued image data by calculating an n-bit logical sum constituting one pixel of the multi-valued image data, and the boundary part discrimination There is disclosed a color image processing apparatus having a processing means for performing a conversion process for changing the number of ink droplets to be superimposed according to a determination result by the means.

JP 2000-108329 A JP 2000-255084 A

  The present invention is a color conversion that can suppress the occurrence of blurring in an image, as compared with a case where a color conversion profile is generated without setting the maximum amount of the slowest ink that is the slowest drying speed for paper. An object is to provide a profile generation device, a color conversion profile generation program, and a color conversion device.

  According to a first aspect of the present invention, there is provided the color conversion profile generation apparatus, wherein the sheet information setting means sets sheet information relating to a sheet on which an image is formed by discharging a plurality of colors of ink, and the sheet information of the plurality of colors of ink. A maximum usage amount setting means for setting the maximum usage amount of the slowest ink with the slowest drying speed for the paper set by the setting means, and an input device within an input color gamut based on the maximum usage amount of the slowest ink; Generating means for generating a color conversion profile for converting the color value into a color value in the output color gamut of the output device.

  According to a second aspect of the present invention, the latest ink is a black ink, and the maximum usage amount setting unit sets a UCR rate, which is a ratio of replacing ink other than the latest ink with black ink, to the maximum usage amount. The generation unit generates the color conversion profile based on the set UCR rate.

  According to a third aspect of the present invention, when the latest ink is other than black ink, the maximum usage amount setting means sets a UCR rate that is a ratio of replacing ink other than the black ink with black ink to a predetermined value. Based on the set UCR rate, the generation unit generates a color conversion profile in which the latest ink is equal to or less than the maximum usage amount.

  According to a fourth aspect of the present invention, a color conversion profile generation program causes a computer to function as each unit constituting the color conversion profile generation device according to any one of the first to third aspects.

  According to a fifth aspect of the present invention, there is provided a color conversion apparatus according to any one of the first to third aspects, wherein the color conversion profile generated by the color conversion profile generation apparatus according to any one of the first to third aspects is stored, and the storage means stores the color conversion profile. Color conversion means for converting a color value in the input color gamut of the input device to a color value in the output color gamut of the output device based on the color conversion profile.

  According to the first, fourth, and fifth aspects of the present invention, blurring occurs in the image as compared with the case where the color conversion profile is generated without setting the maximum usage amount of the slowest ink with the slowest drying speed on the paper. It has the effect that it can suppress doing.

  According to the second aspect of the invention, blurring occurs in the image as compared with the case where the UCR rate is set and the color conversion profile is generated regardless of the maximum usage amount of the slowest ink with the slowest drying speed on the paper. It has the effect that it can suppress doing.

  According to the invention described in claim 3, the bleeding occurs in the image as compared with the case where the slowest ink with the slowest drying speed on the paper generates the color conversion profile regardless of the maximum amount of ink other than the black ink. It has the effect that it can suppress doing.

It is a block diagram of a color conversion apparatus. It is a figure which shows an example of a test chart. It is a diagram which shows an example of a UCR rate curve. It is a flowchart of the process performed in a color conversion profile production | generation part.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. FIG. 1 is a block diagram illustrating a functional configuration of the color conversion apparatus 10 according to the present embodiment.

  The color conversion apparatus 10 is provided between the input device 20 and the output device 30 and performs color conversion processing of image data input from the input device 20, and the color conversion unit 12 refers to the color conversion of the image data. A color conversion profile storage unit 14 that stores a color conversion profile (lookup table) to be stored, and a color conversion profile generation unit 16 that generates a color conversion profile stored in the color conversion profile storage unit 14.

  The color conversion apparatus 10 is an output device 30, for example, an image forming apparatus (color printer) that forms a color image on a recording medium by an inkjet method using inks of CMYK (cyan, magenta, yellow, black) colors. It is realized by incorporating it in

  As the input device 20, for example, an information processing terminal realized by a PC (personal computer) or the like is assumed.

  When the input device 20 is the information processing terminal, image data in the RGB color space created while checking the color on the display in the information processing terminal is input to the color conversion unit 12 as a color gamut conversion target. .

  In this color conversion device 10, the color conversion profile generation unit 16 includes an RGB-Lab conversion unit 40, a color gamut compression unit 42, a UCR rate addition unit 44, a paper information setting unit 46, a maximum usage amount setting unit 48, and a UCR rate setting. Unit 50, LabK-CMYK conversion unit 52, and test chart output unit 54.

The RGB-Lab converter 40 converts the color values (R, G, B as an example in the present embodiment) of the image data within the input color gamut of the input device 20, the input device 20, and a plurality of colors (in this embodiment). The color value is converted into a color value on a device-independent color space (in this embodiment, L ^* a ^* b ^* space as an example) that does not depend on the output device 30 that reproduces a plurality of colors based on an element.

The color gamut compression unit 42 converts the color value of the input image data converted by the RGB-Lab conversion unit 40 in the output device 30 in the same color space (in the present embodiment, L ^* a ^* b ^* space as an example). Converts to a color value in the output color gamut.

Although the details will be described later, the UCR rate adding unit 44 is based on the color value of the L ^* a ^* b ^* space that has been color gamut compressed by the color gamut compressing unit 42 and the UCR rate curve set by the UCR rate setting unit 50. A UCR rate is set, and the set UCR rate (the maximum value of K in this embodiment) is added to Lab data and output to the LabK-CMYK conversion unit 52.

  The paper information setting unit 46 sets paper information indicating the type of paper (plain paper, cardboard, recycled paper, glossy paper, etc.) on which a color image is formed by the inkjet method using CMYK inks. The paper information is set, for example, when the user inputs the paper type.

  The maximum usage amount setting unit 48 sets the maximum usage amount of the slowest ink having the slowest drying speed (penetration speed for the paper) for the paper set by the paper information setting unit 46 among the inks of the CMYK colors. In the present embodiment, a case where the latest ink is K color will be described as an example.

  The maximum usage is set, for example, by causing the test chart output unit 54 to output a test chart, determining the maximum usage by referring to the output test chart, and inputting the determined maximum usage by the user. The

  FIG. 2 shows an example of a test chart. A test chart 60 shown in FIG. 2 is obtained by printing test images including characters, patch images, and lines for each usage amount of the latest ink (K ink in this embodiment).

  In the example of FIG. 2, the test chart 60 includes a test including a 100% black character 100A, a black square patch image 100B, and a horizontal line 100C on a Y background 62 printed with Y ink. An image 100 is printed with a usage amount (density) of 100% K ink. Similarly, a test image 90 including a character 90A of "90% black", a black square patch image 90B, and a line 90C which is one horizontal line is printed with a use amount (density) of 90% K ink. . Similarly, the test chart 60 is printed with test images 80, 70... In which the amount of K ink used is reduced by 10%.

  The user refers to the test chart 60 and confirms whether or not bleeding with the Y background 62 has occurred in the test images for each usage amount. Then, the maximum usage amount among the usage amounts of K ink without bleeding is set as the maximum usage amount.

  Note that the test chart 60 may be read by an image reading apparatus, and the read image may be subjected to image processing to automatically determine whether blur has occurred. For example, the thickness of a line included in a test image may be measured by image processing, and it may be determined that bleeding has occurred when the measured line thickness is equal to or greater than a predetermined threshold.

  Further, for example, a lookup table in which the correspondence between the paper information and the maximum usage is determined in advance is stored, and the maximum usage corresponding to the paper information set by the paper information setting unit 46 is obtained from the lookup table. It may be set.

  The UCR rate setting unit 50 sets a UCR rate curve based on the maximum usage amount of K ink set by the maximum usage amount setting unit 48. The UCR rate is a replacement ratio for replacing the K ink with another CMY ink when performing the under-color reduction process that is a process for replacing the K ink with another CMY ink.

For example, as shown in FIG. 3, a UCR rate curve indicating the correspondence between the lightness L ^* and the UCR rate is preset for each maximum usage amount. In the example of FIG. 3, as an example, a UCR rate curve U100 when the maximum usage is 100%, a UCR rate curve U90 when the maximum usage is 90%, and a UCR rate curve U80 when the maximum usage is 80% are shown. Indicated.

  The UCR rate setting unit 50 sets a UCR rate curve U90, for example, when the maximum usage amount of K ink is set to 90%.

The UCR rate adding unit 44 sets and sets the UCR rate corresponding to the value of L ^{* in} the Lab data output from the color gamut compressing unit 42 based on the UCR rate curve set by the UCR rate setting unit 50. The UCR rate is added to the Lab data as the maximum value of K and output to the LabK-CMYK conversion unit 52.

For example, when the maximum usage amount of K ink is set to 90% and the UCR rate curve U90 is set, if the value of L ^* is “20” as shown in FIG. 3, the UCR rate is set to “90”. If the value of L ^* is “40”, the UCR rate is set to “80”, and if the value of L ^* is “50”, the UCR rate is set to “60”.

  The LabK-CMYK conversion unit 52 converts the four color values of LabK obtained by adding the maximum value of K as the UCR rate to the Lab data output from the UCR rate addition unit 44 into four color values of CMYK. For this conversion, for example, a known method for converting by a learning model using a neural network, for example, a method described in JP-A-9-214789, JP-A-2005-176260, or the like is used.

  Then, the LabK-CMYK conversion unit 52 generates a color conversion profile for converting the color value in the RGB space of the input device 20 to the color value in the CMYK space of the output device 30 based on the conversion result, and the color conversion profile The data is stored in the storage unit 14.

  Next, as an operation of the present embodiment, a color conversion profile generation process will be described with reference to a flowchart shown in FIG. Note that the process shown in FIG. 4 is executed when the user instructs generation of a color conversion profile. Then, the user designates the type of paper for which a color conversion profile is to be generated.

  In step S100, the paper information setting unit 46 sets paper information indicating the type of paper input by the user.

  In step S102, the test chart output unit 54 outputs the test chart shown in FIG.

  In step S104, the maximum usage amount setting unit 48 sets the maximum usage amount of black ink. Specifically, the user refers to the output test chart and confirms whether or not the test image for each usage amount is blurred. Then, the maximum usage amount of the black ink usage amount without bleeding is set as the maximum usage amount. It should be noted that the test chart 60 is read by an image reading device, and the read image is subjected to image processing to determine whether or not bleeding occurs in each usage amount test image. The usage amount may be set as the maximum usage amount. Further, the maximum usage amount corresponding to the paper information set by the paper information setting unit 46 may be obtained and set from a lookup table in which the correspondence between the paper information and the maximum usage amount is determined in advance.

  In step S <b> 106, the UCR rate setting unit 50 sets a UCR rate curve based on the maximum usage amount of K ink set by the maximum usage amount setting unit 48. That is, as shown in FIG. 3, for example, when the maximum use amount of K ink is set to 90%, a UCR rate curve U90 is set.

  In step S108, the RGB-Lab converter 40 converts the RGB data in the input color gamut of the input device 20 into Lab data.

  In step S <b> 110, the color gamut compression unit 42 performs color gamut compression on the Lab data in the input color gamut converted by the RGB-Lab conversion unit 40 to Lab data in the output color gamut of the output device 30. That is, color gamut mapping is performed.

In step S112, the UCR rate addition unit 44 sets the UCR rate corresponding to the L ^* value of the Lab data color gamut compressed by the color gamut compression unit 42 based on the UCR rate curve set by the UCR rate setting unit 50. Then, the set UCR rate is added to the Lab data and output to the LabK-CMYK conversion unit 52 as LabK data.

  In step S114, the LabK-CMYK conversion unit 52 converts the LabK data output from the UCR rate addition unit 44 into CMYK data. This conversion is performed using a learning model using a neural network as described above.

  Note that the processing in steps S108 to S114 is executed for each of the RGB data of each grid point in the input color gamut.

  In step S116, the LabK-CMYK conversion unit 52 converts the color value in the RGB space of the input device 20 into the color in the CMYK space of the output device 30 based on the conversion result in steps S108 to S114 for each grid point in the input color gamut. A color conversion profile for conversion to a value is generated and stored in the color conversion profile storage unit 14.

  As described above, in this embodiment, the maximum usage amount of the slowest ink having the slowest drying speed on the paper is set, and the color value in the input color gamut of the input device 20 is set based on the set maximum usage amount of the slowest ink. Is converted to a color value within the output color gamut of the output device 30.

  In this embodiment, the case where the latest ink is a black ink has been described. However, when the latest ink is a color other than black, for example, magenta, the UCR rate is set to a predetermined value (for example, 100%). ) And the LabK-CMYK converter 52 converts the LabK data to CMYK data. If the magenta conversion result exceeds the maximum use amount of magenta, the process of converting LabK data into CMYK data may be repeated until the magenta conversion result is equal to or less than the maximum use amount of magenta. .

  Further, the configuration of the color conversion apparatus 10 described in the present embodiment (see FIG. 1) is an example, and unnecessary portions are deleted or new portions are added within a range not departing from the gist of the present invention. Needless to say.

10 color conversion device 12 color conversion unit 14 color conversion profile storage unit 16 color conversion profile generation unit 20 input device 30 output device 40 RGB-Lab conversion unit 42 color gamut compression unit 44 UCR rate addition unit 46 paper information setting unit 48 maximum use Quantity setting unit 50 UCR rate setting unit 52 LabK-CMYK conversion unit 54 Test chart output unit 60 Test chart

Claims (5)

Paper information setting means for setting paper information relating to paper on which an image is formed by discharging a plurality of colors of ink;
A maximum usage amount setting means for setting a maximum usage amount of the slowest ink with the slowest drying speed for the paper set by the paper information setting means among the plurality of colors of ink;
Generating means for generating a color conversion profile for converting a color value in the input color gamut of the input device into a color value in the output color gamut of the output device, based on the maximum usage amount of the latest ink;
A color conversion profile generation apparatus comprising: The latest ink is black ink, and the maximum usage amount setting means sets a UCR rate, which is a ratio of replacing ink other than the latest ink with black ink, based on the maximum usage amount, and the generation means The color conversion profile generation device according to claim 1, wherein the color conversion profile is generated based on the set UCR rate. When the latest ink is other than black ink, the maximum usage amount setting unit sets a UCR rate, which is a ratio of replacing ink other than the black ink with black ink, to a predetermined value, and the generation unit includes: The color conversion profile generation apparatus according to claim 1, wherein a color conversion profile is generated based on the set UCR rate so that the latest ink is equal to or less than the maximum usage amount.   A color conversion profile generation program for causing a computer to function as each means constituting the color conversion profile generation apparatus according to any one of claims 1 to 3. Storage means for storing a color conversion profile generated by the color conversion profile generation apparatus according to any one of claims 1 to 3,
Color conversion means for converting a color value in the input color gamut of the input device to a color value in the output color gamut of the output device based on the color conversion profile stored in the storage means;
A color conversion device comprising:

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