Method and apparatus for image data transformation

• US 8,593,480 B1
• Filed: 08/12/2013
• Issued: 11/26/2013
• Est. Priority Date: 03/15/2011
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Ballestad, Anders, Kostin, Andrey
• Primary Examiner(s): Sajous, Wesner
• Application Number:
  US13/964,295
• Publication Number:
  US 20130328907A1
• Time in Patent Office: 106 Days
• Field of Search: 345/581, 345/586, 345589-591, 345/600, 345/606, 345616-618, 345/643, 345/204, 345/690, 345/20, 345/48, 345/63, 345/77, 345/84, 348251-254, 348/241, 348/533, 348/602, 348606-607, 348/615, 348/655, 348/673, 348/683, 348/687, 358515-518, 358/525, 358/533
• US Class Current: 345/590
• CPC Class Codes: G06T 11/001 Texturing; Colouring; Generation of texture or colour inpainting G06T5/77
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 5/02 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 Class Codes: H04N 1/6027 Correction or control of colour gradation or colour contrast H04N1/6058 takes precedence
• CPC Class Codes: H04N 1/6088 by viewing conditions, i.e. conditions at picture output
• CPC Class Codes: H04N 1/62 Retouching, i.e. modification of isolated colours only or in isolated picture areas only
• CPC Class Codes: H04N 9/67 for matrixing camera processing pipelines for matrixing of colour signals H04N23/85
• CPC Class Codes: H04N 9/68 for controlling the amplitude of colour signals, e.g. automatic chroma control circuits H04N9/71, H04N9/73 take precedence; camera processing pipelines for controlling the colour saturation of colour signals H04N23/86

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.

Claims

1. A method to improve the display management of images, the method comprising:

receiving 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 an 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, wherein the first anchor point is determined using the black point levels of the reference and target displays, the second anchor point is determined using the white point levels of the reference and target displays, and the third anchor point is determined using the mid-point levels of the reference and target displays; and

mapping the input image signal to the output image signal using the determined transfer function.

2. The method of claim 1, wherein determining the transfer function further comprises applying a free parameter, wherein the free parameter adjusts the slope of the transfer function at the third anchor point.

3. The method of claim 1, wherein the first information data is received as part of metadata of the input image signal, wherein the metadata is transmitted by an image encoder to a decoder.

4. The method 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.

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

6. The method 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.

7. A method to improve the display management of images, the method comprising:

receiving reference display information, the reference display information characterizing performance of a reference display by three luminance levels of the reference display;

accessing target display information, the target display information characterizing performance of a target display by three luminance levels of the target display;

determining a transfer function to map pixel values of an input image signal encoded on the reference display to corresponding pixel values for the target display using the reference display information and the target display information, wherein the transfer function comprises three anchor points, each of the three anchor points being determined by at least one of the three luminance levels of the reference display and at least one of the three luminance levels of the target display; and

mapping the input image signal to the output image signal using the determined transfer function.

8. The method of claim 7, wherein the three luminance levels characterizing the performance of the reference display or the target display comprise a black-point level value, a white-point level value, and a mid-point level value.

9. The method of claim 8, 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.

10. The method of claim 7, wherein the reference display information is received as part of metadata of the input image signal, wherein the metadata is transmitted by an image encoder to a decoder.

11. The method of claim 7, wherein the transfer function comprises a transformation according to:

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

13. The method of claim 11, wherein the free parameter (n) is determined according to a desired mid-range contrast, independently of the determined anchor points.