IMAGE PROCESSING APPARATUS AND IMAGE PROCESSING METHOD

• US 20080239355A1
• Filed: 03/28/2008
• Published: 10/02/2008
• Est. Priority Date: 03/30/2007
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Hashii, Yusuke, Suwa, Tetsuya, Goto, Fumitaka, Goto, Fumihiro, Hori, Ayumi
• Granted Patent: US 8,498,016 B2
• Time in Patent Office: Days
• US Class Current: 358/1.9
• CPC Class Codes: H04N 1/56 Processing of colour picture signals H04N1/52 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

Image data can be subjected to a smoothing processing to improve a color reproduction characteristic and an image free from a deteriorated gradation characteristic can be printed. Specifically, the smoothing processing improves the color reproduction characteristic. This smoothing processing may cause a color originally not having the lightness equal to or lower than blacking lightness to be converted to a color having lightness equal to or lower than the blacking lightness. To solve this, such a color is subjected to a gradation adjustment processing to convert the color to the color having the lightness higher than blacking lightness. A gamut mapping does not map such a color on a black point, thus preventing such a color from being broken by the blacking.

Claims

1. An image processing apparatus that executes image processing for each pixel, which includes smoothing processing of image data and color conversion processing of image data that has been subjected to the smoothing processing, said apparatus comprising:

a gradation adjustment unit that adjusts gradation of the image data smoothed by the smoothing processing so that the number of pixels which are converted into a predetermined color by the color conversion processing is made smaller.

2. An image processing apparatus as claimed in claim 1, wherein the predetermined color is a color having a blacking lightness.

3. An image processing apparatus as claimed in claim 2, wherein said gradation adjustment unit converts colors having lightness in a predetermined range including the blacking lightness into colors having lightness higher than the blacking lightness so as to adjust the gradation of image data.

4. An image processing apparatus as claimed in claim 1, wherein the predetermined color is a color having a whitening lightness.

5. An image processing apparatus as claimed in claim 4, wherein said gradation adjustment unit converts colors having lightness in a predetermined range including the whitening lightness into colors having lightness lower than the whitening lightness so as to adjust the gradation of image data.

6. An image processing apparatus as claimed in claim 2, wherein said gradation adjustment unit, for colors having lightness in a predetermined range including the blacking lightness, makes a difference of pixel values between pixels in the predetermined range greater so as to adjust the gradation of image data.

7. An image processing apparatus as claimed in claim 4, wherein said gradation adjustment unit, for colors having lightness in a predetermined range including the whitening lightness, makes a difference of pixel values between pixels in the predetermined range greater so as to adjust the gradation of image data.

8. An image processing method of executing image processing for each pixel, which includes smoothing processing of image data and color conversion processing of image data that has been subjected to the smoothing processing, said method comprising the step of:

adjusting gradation of the image data smoothed by the smoothing processing so that the number of pixels which are converted into a predetermined color by the color conversion processing is made smaller.

9. A program that causes a computer to function as an image processing apparatus that executes image processing for each pixel, which includes smoothing processing of image data and color conversion processing of image data that has been subjected to the smoothing processing, said apparatus comprising:

a gradation adjustment unit that adjusts gradation of the image data smoothed by the smoothing processing so that the number of pixels which are converted into a predetermined color by the color conversion processing is made smaller.