Color image modification with approximation function

Patent metadata

Field	Value
Publication number	US-10713765-B2
Application number	US-201816489662-A
Country	US
Kind code	B2
Filing date	Mar 1, 2018
Priority date	Mar 3, 2017
Publication date	Jul 14, 2020
Grant date	Jul 14, 2020

Abstract

Color trim data is used in an approximation function to approximate one or more non-linear transformations of image data in an image processing pipeline. The color trim data is derived in one embodiment through a back projection on a colorist system, and the color trim data is used at the time of rendering an image on a display management system.

First claim

What is claimed is:

1. A method for determining coefficients of one or more color correction approximation functions prior to use by one or more target display management systems, the method comprising:
receiving an image represented by first image data in a first color space;
applying a first color space transformation function on the first image data to convert the first image data into second image data in a second color space;
receiving one or more user inputs that define color correction data to be applied in a third color space that is preferred for making color corrections;
applying at least one of a tone mapping function or a color volume mapping function on the second image data in the second color space to produce mapped image data in the second color space;
applying a second color space transformation on the mapped image data in the second color space to convert the mapped image data into third image data in the third color space;
applying the color correction data on the third image data in the third color space to produce first color corrected image data in the third color space;
projecting back the first color corrected image data in the third color space to the second color space to produce second color corrected image data in the second color space, wherein projecting back involves using reverse transformations to reverse the sequence of transformations between the mapped image data in the second color space and the second color corrected image data in the second color space;
determining coefficients of the one or more color correction approximation functions by an approximation function solver, wherein the one or more color correction approximation functions are configured to fit the mapped image data in the second color space and the back-projected second color corrected image data in the second color space to a mode that represents the non-linear relationship between the mapped image data in the second color space and the back-projected second color corrected image data in the second color space, and wherein the approximation function solver is configured to determine the coefficients of the one or more color correction approximation functions such that the one or more color correction approximation functions, when configured with the generated coefficients and applied to the mapped image data in the second color space, approximate the color correction performed on the third image data in the third color space; and
storing or transmitting the coefficients of the one or more color correction approximation functions for use by the one or more target display management systems.

2. The method of claim 1 , the method further comprising:
displaying on a reference display an image using image data based on the first color corrected image data in the third color space.

3. The method of claim 2 , wherein the one or more user inputs is from a colorist who is viewing the reference display.

4. The method of claim 1 , wherein the first color space is an RGB-type color space, the second color space is an IPT-type color space, and the third color space is an RGB-type or HSV-type color space.

5. The method of claim 1 , wherein the tone mapping function maps image data from a high dynamic range used on a source display to a lower dynamic range used on a reference display and wherein the color volume mapping function maps image data from a large color gamut on the source display to a smaller color gamut on the reference display.

6. The method of claim 1 , wherein at least one of the one or more color correction approximation functions is a linear approximation function and wherein determining the coefficients of the one or more color correction approximation functions involves using multivariate regression to derive the coefficients.

7. The method of claim 1 , wherein the projecting back occurs in response to a user input after viewing an image based on the first color corrected image data.

8. A data processing system comprising a memory and a processing system coupled to the memory, the processing system configured to perform a method as recited in claim 1 .

9. A non-transitory machine readable medium storing instructions which when executed by a data processing system cause the data processing system to perform a method as recited in claim 1 .

Assignees

• Dolby Laboratories Licensing Corp

Inventors

• Partin Alexander
• Thurston Iii Kimball Darr
• Georgiadis Georgios

Classifications

• H04N9/67

  for matrixing (camera processing pipelines for matrixing of colour signals H04N23/85) · CPC title

• H04N1/60 Primary

  Colour correction or control {(H04N1/54 takes precedence)} · CPC title

• G09G5/02

  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)} · CPC title

• G09G2340/06

  Colour space transformation · CPC title

• G06T5/50

  using two or more images, e.g. averaging or subtraction · CPC title