Digital color representation

• US 5,130,701 A
• Filed: 05/12/1989
• Issued: 07/14/1992
• Est. Priority Date: 05/12/1989
• Status: Expired due to Term

• Current Assignee: Los Alamos National Security LLC (Government of the United States of America)
• Original Assignee: United States Department of Energy (Government of the United States of America)
• Inventors: White, James M., Faber, Vance, Saltzman, Jeffrey S.
• Primary Examiner(s): Weldon, Ulysses
• Assistant Examiner(s): FATAHI YAR, MAHMOUD
• Application Number:
  US07/350,675
• Time in Patent Office: 1,159 Days
• Field of Search: 340/701, 340/702, 340/703, 358/80, 358/81, 358/133, 364/521
• US Class Current: 345/601
• CPC Class Codes: G09G 5/06 using colour palettes, e.g. look-up tables

Abstract

An image population having a large number of attributes is processed to form a display population with a predetermined smaller number of attributes which represent the larger number of attributes. In a particular application, the color values in an image are compressed for storage in a discrete lookup table (LUT) where an 8-bit data signal is enabled to form a display of 24-bit color values. The LUT is formed in a sampling and averaging process from the image color values with no requirement to define discrete Voronoi regions for color compression. Image color values are assigned 8-bit pointers to their closest LUT value whereby data processing requires only the 8-bit pointer value to provide 24-bit color values from the LUT.

Claims

1. A method for generating a compressed representation of image pixel colors using stored color values in a lookup table (LUT) to form display pixel colors, comprising the steps of:

sampling said image pixel colors with equal probability to generate a first set of said stored color values;

sampling said image pixel colors with equal probability to generate a sequence of actual image colors;

determining a closest one of said stored color values to each of said actual image colors;

forming an average color value from said closest one of said stored color values and said actual image color; and

updating said closest one of said stored color values with said average color value.

2. A method according to claim 1, wherein forming said average color value includes the step of weighting said closest color value with a weighting factor functionally related to the number of times said closest color value has been updated.

3. A method according to claim 2, where said weighting factor for said stored color value is the number of times said stored color value has been updated divided by one plus the number of updates.

4. A method according to claim 3, further including the step of weighting said sampled image color value by a factor one minus said weighting factor for said stored color value.

5. A method according to claim 1, wherein said image pixel colors are sampled a predetermined number of times to form a final LUT from said averaged color values effective to form a color display approximating said color image.

6. A method according to claim 5, wherein the step of forming said color display includes determining for each pixel color in said image an address in said final LUT of the closest stored color value.

7. A method according to claim 6, further including the step of refining a color space containing said stored color values into a plurality of adaptive volumes in said color space wherein each said adaptive volume defines a predetermined maximum number of said LUT stored color values which are closest to interior points of said volume.

8. A method for generating a compressed representation of image pixel colors using stored color values in a lookup table (LUT) to form display pixel colors, comprising the steps of:

sampling said image pixel colors with equal probability to generate a first set of said stored color values;

sampling said image pixel colors with equal probability to generate a sequence of actual image colors;

selecting a closest one of said stored color values to each of said actual image colors;

forming an average color value from a weighted value of said closest one of said stored color values with a weighting factor functionally related to the number of times said closest color value has been selected and from said actual image color;

updating said closest one of said stored color values with said average color value,

wherein said image pixel colors are sampled a predetermined number of times to form a final LUT from said averaged color values effective to form a color display approximating said color image; and

determining for each pixel color in said image an address in said final LUT of the closest stored color value to represent said image pixel color as said display pixel color.

9. A method according to claim 8, further including the step of refining a color space containing said stored color values into a plurality of adaptive volumes in said color space wherein each said adaptive volume defines a predetermined maximum number of said LUT stored color values which are closest to interior points of said volume.

10. A method according to claim 9, where said weighting factor for said stored color value is the number of times said stored color value has been updated divided by one plus the number of updates and said sampled image color value is weighted by a factor one minus said weighting factor for said stored color value.