Image processing method and apparatus for adjusting a dynamic range of an image

Patent metadata

Field	Value
Publication number	US-11030729-B2
Application number	US-201916281606-A
Country	US
Kind code	B2
Filing date	Feb 21, 2019
Priority date	Aug 22, 2016
Publication date	Jun 8, 2021
Grant date	Jun 8, 2021

Abstract

An image processing method and apparatus, where the method includes determining a maximum value in nonlinear primary color values of all components of each pixel of a first to-be-processed image, determining dynamic parameters of a first transfer function, converting the maximum value of each pixel into a transfer value based on the first transfer function for which the dynamic parameters are determined, calculating a ratio between the transfer value and the maximum value of each pixel, and adjusting a dynamic range for the nonlinear primary color values of all the components of each pixel based on the ratio to obtain nonlinear primary color values of all components of each corresponding pixel of a first target image.

First claim

What is claimed is:

1. An image processing method, comprising:
determining a maximum value in nonlinear primary color values of all components of each pixel of a first to-be-processed image;
determining dynamic parameters of a first transfer function comprising a reversed S-shaped transfer curve, wherein a form of the reversed S-shaped transfer curve is as follows:

L
′

=

1

p
×

(

L
-
b

a

)

-

1
m

-
p
+
1

,

wherein the L is the maximum value in the nonlinear primary color values of all the components of each pixel of the first to-be-processed image, wherein the L′ is the transfer value, and wherein parameters the a, the b, the p, and the m are dynamic parameters of the reversed S-shaped transfer curve;
converting the maximum value of each pixel into a transfer value based on the first transfer function for which the dynamic parameters are determined;
calculating a ratio between the transfer value and the maximum value of each pixel; and
adjusting a dynamic range for the nonlinear primary color values of all the components of each pixel based on the ratio to obtain nonlinear primary color values of all components of each corresponding pixel of a first target image.

2. The image processing method of claim 1 , wherein adjusting the dynamic range for the nonlinear primary color values of all the components of each pixel based on the ratio comprises:
performing an adjustment of narrowing down the dynamic range for the nonlinear primary color values of all the components of each pixel based on the ratio when an image dynamic range of the first to-be-processed image is greater than an image dynamic range of the first target image; and
performing an adjustment of expanding the dynamic range for the nonlinear primary color values of all the components of each pixel based on the ratio when the image dynamic range of the first to-be-processed image is less than the image dynamic range of the first target image.

3. The image processing method of claim 1 , wherein adjusting the dynamic range for the nonlinear primary color values of all the components of each pixel based on the ratio comprises calculating a product of the ratio and each of the nonlinear primary color values of all the components of each pixel to obtain nonlinear primary color values of all the components of each pixel after the adjustment.

4. The image processing method of claim 1 , wherein after obtaining the nonlinear primary color values of all the components of each corresponding pixel of the first target image, the method further comprises converting the nonlinear primary color values of all the components of each pixel of the first target image into linear primary color values of all components of a corresponding pixel of a second target image based on a second transfer function.

5. The image processing method of claim 4 , wherein after converting the nonlinear primary color values of all the components of each pixel of the first target image into the linear primary color values of all the components of the corresponding pixel of the second target image, the method further comprises converting the linear primary color values of all the components of the corresponding pixel of the second target image into nonlinear primary color values of all the components of the corresponding pixel of the second target image based on a third transfer function.

6. The image processing method of claim 1 , wherein before determining the maximum value in the nonlinear primary color values of all the components of each pixel of the first to-be-processed image, the method further comprises converting linear primary color values of all components of each pixel of a second to-be-processed image into nonlinear primary color values of all components of a corresponding pixel of the first to-be-processed image based on a fourth transfer function.

7. The image processing method of claim 6 , wherein before converting the linear primary color values of all the components of each pixel of the second to-be-processed image into the nonlinear primary color values of all the components of the corresponding pixel of the first to-be-processed image, the method further comprises converting nonlinear primary color values of all the components of each pixel of the second to-be-processed image into linear primary color values of all components of a corresponding pixel of the second to-be-processed image based on a fifth transfer function.

8. The image processing method of claim 5 , wherein the first to-be-processed image is a high dynamic range image, wherein the second target image is a standard dynamic range image, wherein the second transfer function comprises a high dynamic range electro-optical transfer function, and wherein the third transfer function comprises a standard dynamic range optical-electro transfer function.

9. The image processing method of claim 7 , wherein the second to-be-processed image is a standard dynamic range image, wherein the first target image is a high dynamic range image, wherein the fourth transfer function comprises a high dynamic range optical-electro transfer function, and wherein the fifth transfer function comprises a standard dynamic range electro-optical transfer function.

10. The image processing method of claim 1 , wherein the first to-be-processed image is a first high dynamic range image, wherein the first target image is a second high dynamic range image, and wherein a dynamic range of the first high dynamic range image is different from a dynamic range of the second high dynamic range image.

11. The image processing method of claim 1 , wherein the first to-be-processed image belongs to a first to-be-processed image sequence, wherein the first target image belongs to a first target image sequence, and wherein determining the dynamic parameters of the first transfer function comprises obtaining the dynamic parameters based on at least one of the following information:
statistics of the first to-be-processed image or statistics of the first to-be-processed image sequence;
a first reference value of a range of the first to-be-processed image or a first reference value of a range of the first to-be-processed image sequence;
a second reference value of the range of the first to-be-processed image or a second reference value of the range of the first to-be-processed image sequence;
a first reference value of a range of the first target image or a first reference value of a range of the first target image sequence; or
a second reference value of the range of the first target image or a second reference value of the range of the first target image sequence.

Assignees

• Huawei Tech Co Ltd

Inventors

• Li Meng
• Chen Hai
• Zheng Jianhua

Classifications

• G09G5/00 Primary

  Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators (image data processing or generation, in general G06T) · CPC title

• H04N19/85

  using pre-processing or post-processing specially adapted for video compression · CPC title

• G06T2207/20208

  High dynamic range [HDR] image processing · CPC title

• G06T2207/10024

  Color image · CPC title

• G06T5/009 Primary

  Physics · mapped topic