Color image processing apparatus

• US 5,844,699 A
• Filed: 06/07/1995
• Issued: 12/01/1998
• Est. Priority Date: 11/15/1990
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Horie, Yoshiko, Ohta, Eiji, Kawai, Takashi, Ohta, Ken-ichi, Usami, Akihiro, Shono, Seita
• Primary Examiner(s): Lee, Thomas D.
• Assistant Examiner(s): Grant, II, Jerome
• Application Number:
  US08/471,881
• Time in Patent Office: 1,273 Days
• Field of Search: 358/500, 358/501, 358/518, 358/519, 358/520, 358/522, 358/523, 358/524, 358/530, 358/537, 358/538, 382/167, 382/168
• US Class Current: 358/518
• CPC Class Codes: H04N 1/6027 Correction or control of colour gradation or colour contrast H04N1/6058 takes precedence
• CPC Class Codes: H04N 1/6058 Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut

Abstract

An image conversion apparatus for image-converting input color image signals, and outputting the converted signals to an output apparatus, allows execution of a plurality of different color processing operations, checks if an input color image falls within a color reproduction region of the output apparatus, and changes the color conversion processing result to be output depending on whether or not the input color image falls within the color reproduction region of the output apparatus. For example, when the input color image falls within the color reproduction region of the output apparatus, color reproduction color-matched with input color image signals is performed. When the input color image falls outside the reproduction region, color reproduction is performed by color conversion processing assuring highest color reproducibility.

Claims

1. A color image processing apparatus comprising:

input means for inputting color image data representing a color image of interest;

memory means for storing a color gamut of an output device, represented with a hexahedron comprising substantially red, green, blue, cyan, magenta, yellow, white and black color-component points;

extraction means for extracting a color gamut of the color image of interest and for determining whether or not the color gamut of the color image of interest is within the color gamut of the output device; and

color-gamut mapping means for mapping the color image data based on the result from extraction by the extraction means,

wherein said color-gamut mapping means performs mapping in a set mapping mode based on the result from the extraction by said extraction means, and

wherein said color-gamut mapping means performs mapping in a first mode in which color image data is reproduced within a color gamut of an output device with high fidelity, or performs mapping in a second mode, if the color image includes color image data outside of the color gamut of the output device, in which color image data is color-gamut-mapped so as to maintain contrast of the color image.

2. The color image processing apparatus according to claim 1, wherein said extraction means extracts the color gamut of the color image of interest at prescanning time.

3. The color image processing apparatus according to claim 1, further comprising:

a scanner for inputting the color image data; and

image formation means for forming an image based on the color image data mapped by said color-gamut mapping means.

4. The color image processing apparatus according to claim 1, wherein said color-gamut mapping means uses a look-up table for mapping the color image data.

5. The color image processing apparatus according to claim 1, wherein said color-gamut mapping means performs a matrix operation for mapping the color image data.

6. The color image processing apparatus according to claim 1, wherein said extraction means extracts color distribution of the color image data.

7. A color image processing apparatus comprising:

input means for inputting color image data representing a color image of interest;

selection means for selecting one of plural mapping modes; and

mapping means for color-gamut mapping the color image data based on the mapping mode selected by said selection means,

wherein said plural mapping modes include;

a first mode for reproducing the color image data within a color gamut of an output device so that the color image data has a high fidelity;

a second mode for mapping color image data outside of the color gamut of the output device into the color gamut of the output device; and

a third mode for mapping the color image data so as to enlarge a gamut of the color image of interest.

8. The color image processing apparatus according to claim 7, wherein the third mode is directed to a map image.

9. The color image processing apparatus according to claim 7, wherein said selection means selects a mapping mode in accordance with manual operation.

10. The color image processing apparatus according to claim 7, wherein said selection means automatically selects a mapping mode.

11. The color image processing apparatus according to claim 7, wherein in the first mode, a look-up table is used for mapping the color image data.

12. The color image processing apparatus according to claim 7, wherein in the second mode, a matrix operation is performed for mapping the color image data.

13. The color image processing apparatus according to claim 7, wherein in the second mode, one of plural color-gamut mapping methods is used in correspondence with the color gamut of the color image data.

14. The color image processing method according to claim 7, further comprising image formation means for forming an image based on the color image data mapped by said color-gamut mapping means.

15. A color image processing apparatus comprising:

input means for inputting color image data representing a color image of interest;

memory means for storing color-gamut mapping data corresponding to a plurality of color gamuts;

extraction means for extracting information on a color gamut of the color image of interest;

setting means for automatically setting the color-gamut mapping data based on the information on the color gamut of the image data; and

color-gamut mapping means for mapping the color image data based on the color-gamut mapping data set by said setting means.

16. The color image processing apparatus according to claim 15, wherein the color-gamut mapping data is indicative of matrix coefficients.

17. The color image processing apparatus according to claim 15, wherein said extraction means extracts the color gamut of the image data at prescanning time.

18. The color image processing apparatus according to claim 15, wherein the color-gamut mapping data is indicative of a look-up table.

19. The color image processing method according to claim 15, further comprising image formation means for forming an image based on the color image data mapped by said color-gamut mapping means.

20. A color processing method comprising:

an input step of inputting color image data representing a color image interest;

a selection step of selecting one of plural mapping modes; and

a mapping step of mapping the color image data based on the mapping mode selected in said selection step,

wherein said plural mapping modes include;

a first mode for reproducing color image data with a high fidelity within a color gamut of an output device;

a second mode for mapping color image data outside of the color gamut of the output device into the color gamut of the output device; and

a third mode for mapping the color image data so as to enlarge a gamut of the color image of interest.

21. A color image processing method comprising:

an input step of inputting color image data representing a color image of interest;

a memory step of storing color-gamut mapping data corresponding to a plurality of color gamuts;

an extraction step of extracting information on a color gamut of the color image of interest;

a setting step of automatically setting the color-gamut mapping data based on the information on the color gamut of the image data; and

a color gamut mapping step of mapping the color image data based on the color-gamut mapping data set in said setting step.