METHOD FOR RENDERING COLOR IMAGES

• US 20200137263A1
• Filed: 12/31/2019
• Published: 04/30/2020
• Est. Priority Date: 05/24/2016
• Status: Active Grant

• Current Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Original Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Inventors: CROUNSE, Kenneth R.
• Granted Patent: US 10,771,652 B2
• Time in Patent Office: Days
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 3/2051 with use of a spatial dither pattern
• CPC Class Codes: G09G 3/2059 using error diffusion
• CPC Class Codes: G09G 3/344 based on particles moving in a fluid or in a gas, e.g. electrophoretic devices electrophoretic devices per se G02F1/167
• CPC Class Codes: H04N 1/405 Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels
• CPC Class Codes: H04N 1/52 Circuits or arrangements for halftone screening
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence

Abstract

An image is rendered on a display having a limited number of primary colors by (104) combining input data representing the color of a pixel to be rendered with error data to form modified input data, determining in a color space the simplex (208—typically a tetrahedron) enclosing the modified input data and the primary colors associated with the simplex, converting (210) the modified image data to barycentric coordinates based upon the primary colors associated with the simplex and (212) setting output data to the primary having the largest barycentric coordinate. calculating (214) the difference between the modified input data and the output data for the pixel, thus generating error data, applying (106) this error data to at least one later-rendered pixel, and applying the output data to the display and thus rendering the image on the display. Apparatus and computer-storage media for carrying out this process are also provided.

Claims

1. A method of rendering an image on a plurality of pixels of a display, wherein each of the plurality of pixels can display any one of a complete set of display primary colors, the method comprising:

receiving input data representing colors to be displayed at each of the plurality of pixels;

combining the input data with error data to create modified input data;

determining in a color space a simplex enclosing the modified input data, wherein the vertices of the simplex comprise a subset of the display primary colors that is smaller than the complete set of display primary colors, hereafter a simplex primary color;

setting output data for a first pixel corresponding to one of the simplex primary colors; and

calculating a difference between the modified input data for the first pixel and the output data for the first pixel, thereby generating new error data for the first pixel;

combining input data for a second pixel with the new error data for the first pixel to create new modified input data for the second pixel;

determining in the color space a new simplex enclosing the modified input data and the new modified input data for the second pixel, wherein the vertices of the new simplex comprise a subset of the display primary colors that is smaller than the complete set of display primary colors, hereafter a new simplex primary color; and

setting output data for the second pixel corresponding to one of the new simplex primary colors.

2. The method of claim 1 further comprising testing the modified input data to determine whether it is within the color gamut of the display and, if the modified input data is outside this color gamut, further modifying the modified input data by projecting the modified input data on to the color gamut to produce projected input data which are used in place of the modified input data in the later stages of the method.

3. The method of claim 2 wherein the projection of the modified input data is effected towards the neutral axis of the color space along a line of constant lightness and hue.

4. The method of claim 2 wherein the projection of the modified input data is effected towards the color represented by the input data for the pixel until the boundary of the color gamut is reached.

5. The method of claim 2 wherein the projected input data is used for the generation of the error data.

6. The method of claim 1 wherein the color space is three-dimensional so that the simplex is a tetrahedron.

9. A non-transitory computer storage medium comprising instructions that when executed by a processor cause the processor to carry out the method of claim 1.

7. The method of claim I wherein the new error data for the first pixel is used in the processing of input data for a third pixel.

8. The method of claim I wherein the display is an electrophoretic display.