Method and apparatus for image data transformation

Patent metadata

Field	Value
Publication number	US-9916809-B2
Application number	US-201514943821-A
Country	US
Kind code	B2
Filing date	Nov 17, 2015
Priority date	Mar 15, 2011
Publication date	Mar 13, 2018
Grant date	Mar 13, 2018

Abstract

Image data is transformed for display on a target display. A sigmoidal transfer function provides a free parameter controlling min-tone contrast. The transfer function may be dynamically adjusted to accommodate changing ambient lighting conditions. The transformation may be selected so as to automatically adapt image data for display on a target display in a way that substantially preserves creative intent embodied in the image data. The image data may be video data.

First claim

What is claimed is:

1. An apparatus for the display management of images, the apparatus comprising:
an input to receive an input image signal;
an input to access first information data for a reference display, the first information data comprising a black point level, a white point level, and a mid-point level of the reference display;
an input to access second information data for a target display, the second information data comprising a black point level, a white point level, and a mid-point level of the target display;
a processor to determine a transfer function to map pixel values of the input image signal to corresponding pixel values of an output image signal using the first and second information data, wherein the transfer function comprises three anchor points that are fixed with the black point levels, the white point levels, and the mid-point levels, of the reference and target displays as indicated by the first and second information, wherein the first anchor point in the three anchor points is determined using the black point levels of the reference and target displays, the second anchor point in the three anchor points is determined using the white point levels of the reference and target displays, and the third anchor point in the three anchor points is determined using the mid-point levels of the reference and target displays;
wherein the processor adjusts the transfer function with a free parameter that does not affect the three anchor points;
a processor to map the input image signal to the output image signal using the determined transfer function; and
an output to output the generated output image signal.

2. The apparatus of claim 1 , wherein the free parameter adjusts the slope of the transfer function at the third anchor point.

3. The apparatus of claim 1 , wherein the first information data is received as part of metadata of the input image signal.

4. The apparatus of claim 3 , wherein the first information data is determined for a scene of the input image signal.

5. The apparatus of claim 1 , further comprising a processor to generate the first information data based on the characteristics of the input image signal.

6. The apparatus of claim 5 , wherein the black point of the reference display is determined as a small percentile of the luminance channel of the input signal.

7. The apparatus of claim 5 , wherein the white point of the reference display is determined as the maximum value of any color channel of the input signal.

8. The apparatus of claim 1 , wherein the first anchor point has horizontal and vertical coordinates respectively equal to the black point levels of the reference display and the target display, the second anchor point has horizontal and vertical coordinates respectively equal to the white point levels of the reference display and the target display, and the third anchor point has horizontal and vertical coordinates respectively equal to the mid-point levels of the reference display and the target display.

9. The apparatus of claim 1 , wherein the transfer function comprises a transformation according to:

V
′

=

C
1

+

C
2

⁢

V
n

1
+

C
3

⁢

V
n

wherein V denotes an input pixel value, V′ denotes an output pixel value, C 1 , C 2 , and C 3 are parameters determined using the three anchor points, and n denotes the free parameter.

10. The apparatus of claim 1 , wherein the pixel values of the input image comprise color values for two or more color components, and the transfer function is determined for each one of the two or more color components.

11. The apparatus of claim 9 , wherein the free parameter (n) is determined according to the slope of the transfer function in a mid-range region.

12. The apparatus of claim 9 , wherein the free parameter (n) is determined according to a desired mid-range contrast, independently of the determined anchor points.

13. A method for the display management of images, the method comprising:
receiving an input image signal;
accessing first information data for a reference display, the first information data comprising a black point level, a white point level, and a mid-point level of the reference display;
accessing second information data for a target display, the second information data comprising a black point level, a white point level, and a mid-point level of the target display;
determining a transfer function to map pixel values of the input image signal to corresponding pixel values of an output image signal using the first and second information data, wherein the transfer function comprises three anchor points that are fixed with the black point levels, the white point levels, and the mid-point levels, of the reference and target displays as indicated by the first and second information, wherein the first anchor point in the three anchor points is determined using the black point levels of the reference and target displays, the second anchor point in the three anchor points is determined using the white point levels of the reference and target displays, and the third anchor point in the three anchor points is determined using the mid-point levels of the reference and target displays;
wherein the processor adjusts the transfer function with a free parameter that does not affect the three anchor points; and
outputting the generated output image signal.

14. The method of claim 13 , wherein the free parameter adjusts the slope of the transfer function at the third anchor point.

15. The method of claim 13 , wherein the first information data is received as part of metadata of the input image signal.

16. The method of claim 15 , wherein the first information data is determined for a scene of the input image signal.

17. A non-transitory computer-readable medium storing one or more sequences of computer instructions which, when executed by one or more computer processors, cause the one or more computer processors to perform:
receiving an input image signal;
accessing first information data for a reference display, the first information data comprising a black point level, a white point level, and a mid-point level for the reference display;
accessing second information data for a target display, the second information data comprising a black point level, a white point level, and a mid-point level for the target display;
determining a transfer function to map pixel values of the input image signal to corresponding pixel values of an output image signal using the first and second information data, wherein the transfer function comprises three anchor points that are fixed with the black point levels, the white point levels, and the mid-point levels, of the reference and target displays as indicat

Assignees

• Dolby Laboratories Licensing Corp

Inventors

• Ballestad Anders
• Kostin Andrey

Classifications

• G06T11/10

  Texturing; Colouring; Generation of textures or colours (retouching, inpainting or scratch removal G06T5/77) · CPC title

• G09G2320/066

  for control of contrast · CPC title

• G09G2320/0666

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

• H04N1/6027 Primary

  Correction or control of colour gradation or colour contrast (H04N1/6058 takes precedence) · CPC title

• G09G5/02 Primary

  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