Color conversion processing apparatus, color conversion processing method, creation method of color conversion lut and storage medium

Patent metadata

Field	Value
Publication number	US-2019124231-A1
Application number	US-201816221277-A
Country	US
Kind code	A1
Filing date	Dec 14, 2018
Priority date	Jun 24, 2016
Publication date	Apr 25, 2019
Grant date	—

Abstract

The present invention is a color conversion processing apparatus that converts an input image signal value into an output value of an actual color material used in an image forming apparatus, and includes: a derivation unit configured to derive an output value corresponding to the input image signal value for a plurality of virtual color materials smaller in number than the number of actual color materials; and a conversion unit configured to convert the derived output values of the plurality of virtual color materials into the output values of the actual color materials, and each of the plurality of virtual color materials has a density corresponding to each wavelength band obtained by dividing a wavelength range reproduced by the actual color materials being output into a plurality of wavelength bands, and the derivation unit derives the output value corresponding to the input image signal value based on the density corresponding to each of the wavelength bands for the plurality of virtual color materials.

First claim

1 . A color conversion processing apparatus that converts an input image signal value into an output value of an actual color material used in an image forming apparatus, the color conversion processing apparatus comprising:
a derivation unit configured to derive an output value corresponding to the input image signal value for a plurality of virtual color materials smaller in number than the number of actual color materials; and a conversion unit configured to convert the derived output values of the plurality of virtual color materials into the output values of the actual color materials, wherein each of the plurality of virtual color materials has a density corresponding to each wavelength band obtained by dividing a wavelength range reproduced by the actual color materials being output into a plurality of wavelength bands, and the derivation unit derives the output value corresponding to the input image signal value based on the density corresponding to each of the wavelength bands for the plurality of virtual color materials.

2 . The color conversion processing apparatus according to claim 1 , wherein
each of the plurality of virtual color materials has a density corresponding to each wavelength band obtained by dividing a wavelength range reproduced by the actual color materials being output into wavelength bands whose number is not less than three and smaller than the number of actual color materials.

3 . The color conversion processing apparatus according to claim 2 , wherein
the plurality of virtual color materials does not have a density for a wavelength band other than a corresponding wavelength band of each of the wavelength bands.

4 . The color conversion processing apparatus according to claim 2 , wherein
the derivation unit determines the output values of the plurality of virtual color materials so that the density corresponding to each of the wavelength bands changes linearly for the input image signal value.

5 . The color conversion processing apparatus according to claim 1 , further comprising:
an acquisition unit configured to acquire equivalent values in terms of the plurality of virtual color materials per unit amount of the actual color material for each actual color material, wherein the conversion unit determines the output value of each of the actual color materials based on the equivalent values with the output values of the plurality of virtual color materials as a target.

6 . The color conversion processing apparatus according to claim 1 , wherein
the conversion unit converts the output values of the plurality of virtual color materials into the output value of the actual color material in accordance with priority of conversion set to each actual color material.

7 . The color conversion processing apparatus according to claim 6 , wherein
the priority of conversion is set in accordance with the density of each of the actual color materials.

8 . The color conversion processing apparatus according to claim 6 , wherein
the conversion unit finds a plurality of output values that causes the output values of the plurality of virtual color materials to coincide in an actual color material of interest selected in accordance with the priority of conversion from each of the actual color materials and determines the output value of the actual color material of interest from the plurality of output values that is caused to coincide in accordance with characteristics of the actual color material of interest.

9 . The color conversion processing apparatus according to claim 8 , wherein
the color conversion unit determines the output value corresponding to the maximum value of the equivalent values of the actual color material of interest of the plurality of output values that is caused to coincide as the output value of the actual color material of interest.

10 . The color conversion processing apparatus according to claim 8 , wherein
the conversion unit determines the minimum value of the plurality of output values that is caused to coincide as the output value of the actual color material of interest.

11 . The color conversion processing apparatus according to claim 6 , wherein
the conversion unit performs control so that, in a case where a value obtained by accumulating the output value of each actual color material determined by the conversion exceeds a predetermined limit value, the accumulated value of the output value of each of the actual color materials does not exceed the limit value by replacing the output value of an actual color material whose priority is higher in the priority of conversion with the output value of an actual color material whose priority is lower for a plurality of actual color materials exhibiting substantially the same hue.

12 . The color conversion processing apparatus according to claim 11 , wherein
at a point in time at which all the output values of each of the actual color materials are determined, at least one output value of the output values of the plurality of virtual color materials coincides with a total value of the determined output values of the virtual color materials by each of the actual color materials.

13 . The color conversion processing apparatus according to claim 1 , further comprising:
a smoothing unit configured to perform smoothing processing for the output value of each actual color material determined by the conversion unit.

14 . The color conversion processing apparatus according to claim 13 , wherein
the input image signal is three channels of RGB, and the smoothing unit performs the smoothing processing so that the output value of the actual color material at each vertex does not change by using a smoothing filter whose filter size at each of the vertexes of an RGB cube is 0.

15 . The color conversion processing apparatus according to claim 1 , wherein
the input image signal is three channels of RGB, and the derivation unit finds the output values of the plurality of virtual color materials on each axis of an RGB cube and determines the output values of the plurality of virtual color materials between axes of the RGB cube by interpolation processing using the found output values.

16 . The color conversion processing apparatus according to claim 6 , wherein
the input image signal is three channels of RGB, and the conversion unit determines the output value of the actual color material on each line in accordance with priority of conversion set for each line connecting each vertex of an RGB cube, then determines the output value of the actual color material on a plane connecting each line, and then determines the output value of the actual color material inside the RGB cube.

17 . A color conversion processing method of converting an input image signal value into an output value of an actual color material used in an image forming apparatus, the method comprising:
a derivation step of deriving an output value corresponding to the input image signal value for a plurality of virtual color materials smaller in number than the number of actual color materials; and a conversion step of converting the derived output values of the plurality of virtual color materials into the output values of the actual color materials, wherein each of the plurality of virtual color materials has a density corresponding to each wavelength band obtained by dividing a wavelength range reproduced by the actual color materials being output into a plurality of wavelength bands, and at the derivation step, the output values of the plurality of virtual color materials correspondin

Assignees

• Canon Kk

Inventors

• Takesue Naoya
• Dobashi Toshiyuki
• Yanai Tomokazu
• Ishikawa Hisashi

Classifications

• G06T1/00

  General purpose image data processing · CPC title

• H04N1/54 Primary

  Conversion of colour picture signals to a plurality of signals some of which represent particular mixed colours, e.g. for textile printing · CPC title

• H04N1/60

  Colour correction or control {(H04N1/54 takes precedence)} · CPC title

• H04N1/52

  Circuits or arrangements for halftone screening · CPC title

• G06F3/12

  Digital output to print unit {, e.g. line printer, chain printer} · CPC title