Systems and methods for improved gamut mapping from one image data set to another

• US 7,619,637 B2
• Filed: 04/09/2004
• Issued: 11/17/2009
• Est. Priority Date: 04/09/2004
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Group)
• Original Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Inventors: Higgins, Michael Francis, Brown Elliott, Candice Hellen
• Primary Examiner(s): Poon; King Y
• Assistant Examiner(s): Vo; Quang N
• Application Number:
  US10/821,306
• Publication Number:
  US 20050225562A1
• Time in Patent Office: 2,048 Days
• Field of Search: 345/604, 345/88, 345/589, 358/1.12, 382/162, 382/167
• US Class Current: 345/604
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607

Abstract

The present application discloses methods and system for converting input image data in a first color space into image data in a second color space format. Several embodiments disclose improved techniques for performing these conversions using inexpensive hardware and software implementations.

Claims

1. A computer-readable medium having computer-executable instructions for calculating the luminance value from an input image data, said input image data comprising a red (R) digital data value, a green (G) digital data value and a blue (B) digital data value, said luminance value calculation comprising:

shifting said R digital data value to the left by one digital place value, producing a R intermediate digital data value;

shifting said G digital data value to the left by two digital place values, producing a G intermediate digital data value;

adding said R intermediate digital data value to said B digital value, producing a first intermediate value;

adding G digital value to said G intermediate digital data value, producing a second intermediate value;

adding said first intermediate value to said second intermediate value, producing a third intermediate value; and

shifting said third intermediate value by three digital place values, producing said luminance value.

2. The computer-readable medium of claim 1 wherein said luminance value calculation further comprises performing the calculation Y=(2*R+5*G+B)/8, where Y is substantially the luminance value for said input image data.

3. A computer-readable medium having computer-executable instructions for calculating the hue angle of an input image data, said input image data comprising a red (R) digital data value, a green (G) digital data value and a blue (B) digital data value, said hue angle calculation comprising:

calculating a luminance value from said input image data, producing a Y digital value;

calculating intermediate values x=absolute values of B−

Y and y=absolute value of R−

Y;

swapping intermediate values x and y if y>

x;

dividing y by x;

accessing an action look-up table to provide correction bits for performing calculations within the first subset of hue angle space; and

accessing an arctangent look-up table, said arctangent table producing an intermediate hue angle value.

4. The computer-readable medium of claim 3 wherein said calculating of a luminance value comprises performing the calculation Y=(2*R+5*G+B)/8, where Y is substantially the luminance value for said input image data.

5. The computer-readable medium of claim 3 wherein said calculating of a luminance value comprises:

shifting said R digital data value to the left by one digital place value, producing a R intermediate digital data value;

shifting said G digital data value to the left by two digital place values, producing a G intermediate digital data value;

adding said R intermediate digital data value to said B digital value, producing a first intermediate value;

adding G digital value to said G intermediate digital data value, producing a second intermediate value;

adding said first intermediate value to said second intermediate value, producing a third intermediate value; and

shifting said third intermediate value by three digital place values, producing said luminance value.

6. The computer-readable medium of claim 3 wherein said action look-up table provides corrections with the first octant of said hue angle space.

7. A computer-readable medium having computer-executable instructions for converting an RGB input image data into an RGBW image data, said conversion comprising:

calculating the hue angle of said RGB input image data;

selecting the chromaticity triangle of said RGB input image data based upon said hue angle, said chromaticity triangles being selected from one of a group, said group comprising RGW, GBW and BRW;

selecting a multi-primary matrix based upon said chromaticity triangle;

multiplying said multi-primary matrix to said RGB input image data to produce an intermediate RGBW image data value; and

wherein further said multi-primary matrix being selected from one of a group, said group comprising;

8. The computer-readable medium of claim 7 wherein said group of said multi-primary matrices correspond to RGW, GBW, and BRW chromaticity triangles respectively.

9. The computer-readable medium of claim 7 wherein the conversion further comprises:

detecting out-of-gamut image data values;

determining the maximum color component that is out-of-gamut; and

accessing an inverse look-up table for providing a scaling factor to apply to said out-of-gamut image values.

10. The computer-readable medium of claim 7, wherein the conversion further comprises:

subpixel rendering said RGBW image data values; and

accessing an output gamma look-up table for providing gamma values to be applied to image data values from said subpixel rendering module.