Color calibration method and structure for vector error diffusion

• US 20070019217A1
• Filed: 07/24/2005
• Published: 01/25/2007
• Est. Priority Date: 07/24/2005
• Status: Abandoned Application

• Current Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Chang, Ching-Wei
• Application Number:
  US11/188,609
• Publication Number:
  US 20070019217A1
• Time in Patent Office: Days
• US Class Current: 358/1.900
• CPC Class Codes: H04N 1/52 Circuits or arrangements for halftone screening
• CPC Class Codes: H04N 1/6016 Conversion to subtractive colour signals

Abstract

A color calibration method (and related structure) usable in a color-image vector error diffusion system which includes an image input device operating in one color space, and an n-bit, multi-level image output device operating in an output-device-specific version of another color space. The method includes the steps of performing a first image-data conversion which maps image data from the mentioned one color space to a generic version of the mentioned other color space, and thereafter performing a calibrated, second image-data conversion which maps image data from a generic version of the mentioned other color space to the mentioned output-device-specific version of the other color space.

Claims

1. A color calibration method usable in a color-image vector error diffusion system which includes an image input device operating in one color space, and a multi-level image output device operating in an output-device-specific version of another color space, said method comprising

performing a first image-data conversion which maps image data from the mentioned one color space to a generic version of the mentioned other color space, and thereafter

performing a calibrated, second image-data conversion which maps image data from a generic version of the mentioned other color space to the mentioned output-device-specific version of the other color space.

2. The method of claim 1, wherein said first-mentioned performing utilizes a color palette which has been created using a generic profile that relates the mentioned one color space to the generic version of the mentioned other color space.

3. The method of claim 2 which further comprises creating the mentioned color palette employing a reverse conversion procedure which is operatively associated with both the mentioned one color space and the generic version of the mentioned other color space.

4. The method of claim 1, wherein said second-mentioned performing is based upon a precursor procedure involving creating a color palette which is output-device color-calibrated.

5. The method of claim 4, wherein said creating involves examining the actual color outputting produced by the output device.

6. The method of claim 1, wherein the mentioned one color space is drawn from the group including sRGB color space, cRGB color space, and RGB color space.

7. The method of claim 1, wherein the generic version of the mentioned other color space is a generic version of a color space drawn from the group including CMYK color space, CMY color space, and RGB color space.

8. The method of claim 1, wherein the output-device-specific version of the mentioned other color space is a device-specific version of a color space drawn from the group including CMYK color space, CMY color space, and RGB color space.

9. The method of claim 1, wherein the mentioned one color space is sRGB color space, the generic version of the mentioned other color space is a generic version of CMYK color space, and the output-device-specific version of the mentioned other color space is an output-device-specific version of CMYK color space.

10. A method involving vector error diffusion in an color-imaging system employing an image input device and a multi-level image output device, which devices operate in different, respective, associated color spaces, said method comprising

preparing and utilizing at least one output-device-specific color palette which is output-device color-calibrated to perform color-image data conversion that maps color-image data which is en route from the input device to the output device to an output color space which is specifically associated with the output device.

11. The method of claim 10, wherein said preparing and utilizing of the at least one color palette results in mapping of color-image data from a generic version of a specific, nominal color space to a non-generic version of that same color space.

12. The method of claim 11, wherein the nominal color space is CMYK color space.

13. A color calibration method useable in a color-image vector error diffusion system which includes a color-image input device operating on one color space, and a multi-level color-image output device operating in a device-specific-version of another color space, said method comprising

performing a first color-image data conversion to map input-image data from the mentioned one color space to a form of intermediate image data in a generic version of the mentioned other color space, and thereafter

performing a calibrated, second color-image data conversion to map such intermediate image data from the generic version of the other color space to a form of output image data in the mentioned device-specific version of the other color space.

14. The method of claim 13, wherein said first and second performing steps are implemented on the upstream and downstream sides, respectively, of where vector error diffusion takes place.

15. A color calibration method for vector error diffusion effective between a color image input device operating in one color space and a multi-level color image output device operating in another color space, said method comprising

preparing a first color palette for use in a practice of vector error diffusion intermediate such color image input and output devices,

basing that preparing upon a reverse color conversion procedure which is effectively applied to a generated and calibrated color profile associated with the operation of the color image input device, and

creating, intermediate the first color palette in the color image output device, a second color palette in the form of a color-calibrated output color index table.

16. A color calibration organization useable in a color image vector error diffusion system intermediate an upstream color image input device which operates in one, input device color space, and a downstream, multi-level, color image output device which operates in another, output-device color space, said organization comprising

first and second, differently configured color palettes disposed in upstream and downstream relative positions respectively between said input and output devices, wherein said first color palette is constructed to map image data from the mentioned one color space to a generic version of the mentioned other color space, and said second color palette is structured to map image data from a generic version of the mentioned other color space to the mentioned output-device-specific version of the other color space.