Color error diffusion method

• US 7,369,274 B2
• Filed: 09/08/2004
• Issued: 05/06/2008
• Est. Priority Date: 09/08/2004
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Chang, Ching-Wei
• Primary Examiner(s): Williams; Kimberly A.
• Application Number:
  US10/935,763
• Publication Number:
  US 20060061781A1
• Time in Patent Office: 1,336 Days
• Field of Search: 358/1.9, 358/504, 358/518, 358/523, 358/524, 382/162, 382/167, 345/601, 345/602
• US Class Current: 358/1.9
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence

Abstract

A color error diffusion method effective between a color image input device operating in one color space and a color image output device operating in another color space. The method includes the steps of (a) preparing a final color palette for use in a practice of vector error diffusion intermediate the color image input and output devices, and (b) basing that preparing upon a reverse color conversion step which is effectively applied to a generated calibrated color profile associated with operation of the color image input device.

Claims

1. A color error diffusion method effective between a color image input device operating in one color space and a color image output device operating in another color space, said method comprising

preparing a final color palette for use in a final vector error diffusion activity and intermediate color image input and output devices, and

basing that preparing upon a reverse color conversion step which is effectively applied to a generated calibrated color profile associated with operation of the color image input device wherein the basing involves establishing an initial color palette associated directly with the operation of the color image input device, and then, by utilizing that initial color palette in an initial vector error diffusion activity preceding the final vector error diffusion activity as conducted in the color image input device'"'"'s operating color space, generating the generated calibrated color profile.

2. The method of claim 1, wherein the color image input device'"'"'s color space is one selected from the group including sRGB color space, RGB color space and cRGB color space, and the color image output device'"'"'s color space is one selected from the group including CMYK color space and CMY color space.

3. The method of claim 1 further including applying both the initial color palette used in the initial vector error diffusion activity and the final color palette used in the final vector error diffusion activity at the same circuit location when sequentially performing each activity.

4. The method of claim 3 which further includes, intermediate the steps of generating the mentioned generated calibrated color profile, and the ultimate preparing of the final color palette, implementing a step involving producing, from the mentioned generated and calibrated color profile, a color look-up table in relation to which the mentioned reverse color conversion is effectively applied to the generated calibrated color profile.

5. The method of claim 4, wherein the color image input device'"'"'s color space is one selected from the group including sRGB color space, RGB color space and cRGB color space, and the color image output device'"'"'s color space is one selected from the group including CMYK color space and CMY color space.

6. The method of claim 3, wherein the color image input device'"'"'s color space is one selected from the group including sRGB color space, RGB color space and cRGB color space, and the color image output device'"'"'s color space is one selected from the group including CMYK color space and CMY color space.

7. The method of claim 6, wherein the color image input device'"'"'s operating color space is sRGB, and said establishing of the initial color palette involves identifying, with respect to the color image input device, a relationship between its operational sRGB color space and a generic CMYK color space, and the mentioned conducting of vector error diffusion activity is performed in the color image input device'"'"'s sRGB color space.

8. The method of claim 7, wherein the color image input device'"'"'s color space is one selected from the group including sRGB color space, RGB color space and cRGB color space, and the generic color space is one selected from the group including CMY color space and CMYK color space.

9. A color error diffusion method effective between a color image input device operating in one color space and a color image output device operating in another color space, said method comprising

with respect to the color image input device, performing a first color conversion from that device'"'"'s operating color space to a selected transitional color space which is a generic version of the color image output device'"'"'s operating color space,

creating an initial color palette from this first color conversion,

using the created initial color palette in an initial vector error diffusion process, preparing test color calibration images, and from these images generating a calibrated color profile which is associated with the operation of the color image input device,

from the generated calibrated color profile, producing a color look-up table which relates the color image input device'"'"'s operating color space to the color image output device'"'"'s operating color space, and

from the produced look-up table, and employing, effectively, the performance of a second, reverse color conversion step, preparing a final color palette which relates the color image input device'"'"'s operating color space to each of the possible output colors that are producible by the color image output device in its operating color space, and

applying the final color palette intermediate the color image input and output devices including in a final vector error diffusion process performed subsequent to the initial vector error diffusion process.

10. The method of claim 9, wherein the color image input device'"'"'s operating color space is one selected from the group including sRGB color space, RGB color space and cRGB color space, the transitional color space is one selected from the group including CMY color space and CMYK color space, and the color image output device'"'"'s operating color space is one selected from the group including CMY color space and CMYK color space.