DEVICE FOR CHANGING SCREEN RULING FOR IMAGE FORMATION IN ACCORDANCE WITH RELATIONSHIP BETWEEN LUMINANCE AND SATURATION

• US 20090086227A1
• Filed: 09/30/2008
• Published: 04/02/2009
• Est. Priority Date: 10/02/2007
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Nagai, Jun
• Granted Patent: US 8,243,335 B2
• Time in Patent Office: Days
• US Class Current: 358/1.900
• CPC Class Codes: H04N 1/4051 producing a dispersed dots halftone pattern, the dots having substantially the same size different sizes H04N1/4057
• CPC Class Codes: H04N 1/603 controlled by characteristics of the picture signal generator or the picture reproducer

Abstract

The present invention relates to a device that, in printing of controlling the amount of color materials applied, changes a screen ruling for image formation according to the relationship between luminance and saturation. A first component obtains color component data of a plurality of colors so that the total amount of controlled variable in each pixel does not exceed a first limit amount. A second component obtains color component data of a plurality of colors so that the total amount of controlled variable in each pixel does not exceed a second limit amount by performing color conversion processing different from the color conversion processing with the first component. A third component performs pseudo halftone processing by changing a screen ruling to be applied to the color component data of a plurality of colors obtained by the color conversion processing with the second component from chromaticity of color image data.

Claims

1. An image processing device provided with a plurality of colors of color materials, comprising:

a first color conversion component configured to obtain color component data of the plurality of colors so that the total amount of controlled variable in each pixel does not exceed a first limit amount by performing color conversion processing on image data;

a second color conversion component configured to obtain color component data of the plurality of colors so that the total amount of controlled variable in each pixel does not exceed a second limit amount by performing color conversion processing different from that by the first color conversion component on the image data; and

a pseudo halftone processing component configured to obtain a plurality of pseudo halftone data by performing pseudo halftone processing on the color component data of the plurality of colors obtained with the first color conversion component or the second color conversion component,

wherein the pseudo halftone processing component performs pseudo halftone processing by change a screen ruling to be applied to the color component data of the plurality of colors obtained by color conversion processing with the second color conversion component on the basis of chromaticity obtained from the image data.

2. The image processing device of claim 1, wherein the pseudo halftone processing component, in the chromaticity obtained from the image data, changes a screen ruling to be applied to the color component data of the plurality of colors obtained by color conversion processing with the second color conversion component on the basis of luminance and saturation.

3. The image processing device of claim 2, wherein the pseudo halftone processing component, in the chromaticity obtained from the image data, calculates a threshold according to the luminance, and changes a screen ruling to be applied to the color component data of the plurality of colors obtained by color conversion processing with the second color conversion component on the basis of a comparison result between the threshold and the saturation.

4. The image processing device of claim 3, wherein the pseudo halftone processing component, in the chromaticity obtained from the image data, calculates a threshold according to the luminance, compares the threshold and the saturation, and applies a high screen ruling in a region with the saturation not less than the threshold and applies a low screen ruling in a region with the saturation less than the threshold.

5. The image processing device of claim 1, wherein the pseudo halftone processing component, in the chromaticity obtained from the image data, calculates a threshold according to luminance, and on the basis of a comparison result between the threshold and saturation, and an attribute of an object to be applied, changes a screen ruling to be applied to the color component data of the plurality of colors obtained by color conversion processing with the second color conversion component to perform pseudo halftone processing.

6. The image processing device of claim 1, wherein the total amount of controlled variable in the each pixel is the amount of color material applied.

7. The image processing device of claim 2, wherein the total amount of controlled variable in the each pixel is the amount of color material applied.

8. The image processing device of claim 3, wherein the total amount of controlled variable in the each pixel is the amount of color material applied.

9. The image processing device of claim 4, wherein the total amount of controlled variable in the each pixel is the amount of color material applied.

10. The image processing device of claim 5, wherein the total amount of controlled variable in the each pixel is the amount of color material applied.

11. An image processing method in an image processing device provided with a plurality of colors of color materials, comprising:

a first step of obtaining color component data of the plurality of colors so that the total amount of controlled variable in each pixel does not exceed a first limit amount by performing color conversion processing on image data;

a second step of obtaining color component data of the plurality of colors so that the total amount of controlled variable in each pixel does not exceed a second limit amount by performing color conversion processing different from the color conversion processing in the first step on the image data; and

a third step of obtaining a plurality of pseudo halftone data by performing pseudo halftone processing on the color component data of the plurality of colors obtained in the first step or the second step,

wherein, in the third step, the pseudo halftone processing is performed by changing a screen ruling to be applied to the color component data of the plurality of colors obtained by color conversion processing in the second step on the basis of chromaticity obtained from the image data.

12. A computer-readable recording medium having computer-executable instructions for performing the method of claim 11.

13. An image processing device comprising:

a determination component configured to determine whether in each region included in image data, saturation is higher than a saturation threshold or not, and luminance is lower than a luminance threshold or not; and

an application component configured to apply a high screen ruling to a region determined to have saturation higher than the saturation threshold and to have luminance lower than the luminance threshold, while to apply a low screen ruling to a region determined to have saturation lower than the saturation threshold and to have luminance higher than the luminance threshold.

14. The image processing device of claim 13, wherein the determination component further determines a black character region, and wherein the application component further applies a high screen ruling to the black character region.