Method and apparatus for nonlinear interpolation color conversion using look up tables

Patent metadata

Field	Value
Publication number	US-2020007718-A1
Application number	US-201816022999-A
Country	US
Kind code	A1
Filing date	Jun 29, 2018
Priority date	Jun 29, 2018
Publication date	Jan 2, 2020
Grant date	—

Abstract

A method and apparatus obtains a source image having a plurality of source color gamut pixels in a source color gamut. The method and apparatus converts the plurality of source color gamut pixels to a plurality of corresponding target color gamut pixels using non-linear interpolation of a plurality of output pixel values from a reduced 3-D look-up table (LUT) for a target color gamut. The method and apparatus provides, for display, the plurality of target color gamut pixels (e.g., one or more pixels) on a target color gamut display.

First claim

What is claimed is:

1 . A method of mapping between color gamuts comprising:
obtaining, by an apparatus, a source image having a plurality of source color gamut pixels in a source color gamut; converting the plurality of source color gamut pixels to a plurality of corresponding target color gamut pixels using non-linear interpolation of a plurality of output pixel values from a reduced 3 dimensional (3-D) look-up table (LUT) corresponding to a target color gamut; and providing, for display, the plurality of corresponding target color gamut pixels on a target color gamut display.

2 . The method of claim 1 , wherein the converting the plurality of source color gamut pixels to the plurality of corresponding target color gamut pixels comprises performing a first non-linear interpolation for a plurality of first pixel values from the reduced 3-D LUT that is different from a second non-linear interpolation for a plurality of second pixel values from the reduced 3-D LUT.

3 . The method of claim 2 , wherein the plurality of first pixel values from the reduced 3-D LUT correspond to vertices of a sub-cube within the target color gamut and wherein the converting the plurality of source color gamut pixels to the plurality of corresponding target color gamut pixels further comprises:
determining, based on the plurality of first pixel values from the reduced 3-D LUT, a set of polynomial coefficients for the sub-cube, and wherein the performing the first non-linear interpolation is based on the set of polynomial coefficients.

4 . The method of claim 3 , wherein the performing the first non-linear interpolation based on the set of polynomial coefficients is prior to performing a tetrahedral interpolation calculation or a tri-linear interpolation calculation.

5 . The method of claim 3 , wherein a graphics driver calculates the set of polynomial coefficients by performing a Taylor Series transform based on the vertices of the sub-cube within the target color gamut.

6 . The method of claim 2 , wherein the first non-linear interpolation is a piecewise linear curve or a polynomial equation.

7 . The method of claim 1 , wherein the converting the plurality of source color gamut pixels to the plurality of corresponding target color gamut pixels is performed by a 3-D engine.

8 . The method of claim 1 , wherein the converting the plurality of source color gamut pixels to the plurality of corresponding target color gamut pixels is performed by a video encoder, and
wherein the obtaining the plurality of source color gamut pixels comprises obtaining the plurality of source color gamut pixels from a server via an internet connection.

9 . The method of claim 1 , the converting the plurality of source color gamut pixels to the plurality of corresponding target color gamut pixels is performed by a display engine, and
wherein the display engine performs tone mapping operations for the target color gamut display.

10 . An apparatus comprising:
non-linear interpolation color conversion logic configured to:
obtain a source image having a plurality of source color gamut pixels in a source color gamut;
convert the plurality of source color gamut pixels to a plurality of corresponding target color gamut pixels using non-linear interpolation of a plurality of output pixel values from a reduced 3-D LUT corresponding to a target color gamut; and
provide for display the plurality of corresponding target color gamut pixels on a target color gamut display.

11 . The apparatus of claim 10 , wherein the non-linear interpolation color conversion logic converts the plurality of source color gamut pixels to the plurality of corresponding target color gamut pixels by performing a first non-linear interpolation for a plurality of first pixel values from the reduced 3-D LUT that is different from a second non-linear interpolation for a plurality of second pixel values from the reduced 3-D LUT.

12 . The apparatus of claim 11 , wherein the plurality of first pixel values from the reduced 3-D LUT correspond to vertices of a sub-cube within the target color gamut and wherein non-linear interpolation color conversion logic converts the plurality of source color gamut pixels to the plurality of corresponding target color gamut pixels by:
determining, based on the plurality of first pixel values from the reduced 3-D LUT, a set of polynomial coefficients for the sub-cube, and wherein the performing the first non-linear interpolation is based on the set of polynomial coefficients.

13 . The apparatus of claim 12 , wherein the non-linear interpolation color conversion logic performs the first non-linear interpolation prior to performing a tetrahedral interpolation calculation or a tri-linear interpolation calculation.

14 . The apparatus of claim 12 , further comprising:
a processor comprising a graphics driver, wherein the graphics driver is configured to calculate the set of polynomial coefficients by performing a Taylor Series transform based on the vertices of the sub-cube within the target color gamut.

15 . The apparatus of claim 12 , wherein the plurality of second pixel values from the reduced 3-D LUT correspond to vertices of a second sub-cube and wherein non-linear interpolation color conversion logic converts the plurality of source color gamut pixels to the plurality of corresponding target color gamut pixels by:
determining, based on the plurality of second pixel values from the reduced 3-D LUT, a second set of polynomial coefficients for the second sub-cube, wherein the second set of polynomial coefficients is different from the set of polynomial coefficients; and performing the second non-linear interpolation based on the second set of polynomial coefficients.

16 . The apparatus of claim 11 , wherein the first non-linear interpolation is a piecewise linear curve or a polynomial equation.

17 . The apparatus of claim 10 , further comprising:
a video encoder, wherein the video encoder comprises the non-linear interpolation color conversion logic, and wherein the video encoder is configured to:
obtain the plurality of source color gamut pixels from a server via an internet connection.

18 . The apparatus of claim 10 , further comprising:
a display engine, wherein the display engine comprises the non-linear interpolation color conversion logic, and wherein the display engine performs tone mapping operations for the target color gamut display.

19 . The apparatus of claim 10 , further comprising:
a 3-D engine, wherein the 3-D engine comprises the non-linear interpolation color conversion logic; and a texture cache, wherein the texture cache stores the reduced 3-D LUT corresponding to the target color gamut.

20 . An integrated circuit comprising:
a first processor, wherein the first processor comprises:
non-linear interpolation color conversion logic configured to:
obtain a source image having a plurality of source color gamut pixels in a source color gamut;
obtain a reduced 3-D LUT corresponding to a target color gamut, the reduced 3-D LUT comprises a plurality of displayable target color values representing vertices of a plurality of sub-cubes;
select, on a pixel-by-pixel basis, a plurality of pixel values from the plurality of displayable target color values, a plurality of pixel values representing vertices of a sub-cube of the plurality of sub-cubes within the target color gamut;
determine, based on a non-linear interpolation of the vertices of the sub-cube, a set of polynomial coefficients for the s

Assignees

• Ati Technologies Ulc

Inventors

• Lee Keith

Classifications

• G09G3/2003

  Display of colours (specific for liquid crystal displays G09G3/3607) · CPC title

• G09G2320/0666

  for control of colour parameters, e.g. colour temperature · CPC title

• H04N23/741

  by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors · CPC title

• H04N1/6058 Primary

  Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut · CPC title

• G06T1/20

  Processor architectures; Processor configuration, e.g. pipelining · CPC title