Image Formats and Related Methods and Apparatuses

• US 20130076974A1
• Filed: 09/25/2012
• Published: 03/28/2013
• Est. Priority Date: 09/26/2011
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Atkins, Robin
• Granted Patent: US 8,988,552 B2
• Time in Patent Office: Days
• US Class Current: 348/362
• CPC Class Codes: G06T 1/20 Processor architectures; Processor configuration, e.g. pipelining
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• 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: G09G 5/10 Intensity circuits
• CPC Class Codes: H04N 21/42202 environmental sensors, e.g. for detecting temperature, luminosity, pressure, earthquakes
• CPC Class Codes: H04N 21/4318 by altering the content in the rendering process, e.g. blanking, blurring or masking an image region image enhancement or restoration in general G06T5/00
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 23/73 by influencing the exposure time
• CPC Class Codes: H04N 5/262 Studio circuits, e.g. for mixing, switching-over, change of character of image, other special effects ; Cameras specially adapted for the electronic generation of special effects
• CPC Class Codes: H04N 5/57 Control of contrast or brightness

Abstract

Image data may be color graded, distributed and viewed on target displays. Mappings that preserve mid-range points and mid-range contrast may be applied to view the image data for color grading and to prepare the image data for display on a target display. The image data may be expanded to exploit the dynamic range of the target display without affecting mid-tone values.

Claims

1. A method for displaying an image on a target display, the method comprising:

processing image data that has been reviewed on a reference display and encoded such that a predetermined image value of the image data corresponds to a predetermined mid-tone value displayed on the reference display, the processing comprising applying a mapping to the image data that maps the predetermined image value to the predetermined mid-tone value when viewed on the target display, wherein a dynamic range of the target display differs from a dynamic range of the reference display.

2. A method according to claim 1 wherein the mapping provides a log-linear mid-tone region having a slope n that matches a slope of a corresponding mid-tone region of a response function of the reference display.

3. A method according to claim 2 wherein the mapping comprises a mapping function given by:

4. A method according to claim 3 comprising adjusting the mapping in response to ambient lighting.

5. A method according to claim 4 wherein adjusting the mapping comprises increasing the mid-tone value to which the predetermined image value is mapped in response to an increase in the ambient lighting.

6. A method according to claim 5 wherein increasing the mid-tone value comprises adjusting the value of c₂ in the mapping function.

7. A method according to claim 4 wherein adjusting the mapping decreasing mid-tone contrast of the mapping function.

8. A method according to claim 7 wherein decreasing the mid-tone contrast comprises adjusting the value of n.

9. A method according to claim 4 comprising modeling the effect of the ambient lighting on light adaptation of the human visual system to obtain an estimated adaptation and adjusting the mapping based on the estimated adaptation.

10. A method according to claim 9 wherein modeling the effect of the ambient lighting on the adaptation of the human visual system comprises modeling a plurality of adaptation aspects to obtain a corresponding plurality of estimated adaptations and the method comprises adjusting different characteristics of the mappings based on different ones of the estimated adaptations.

11. A method according to claim 10 wherein modeling the effect of the ambient lighting on light adaptation of the human visual system is based at least in part on inputs from one or more ambient light sensors and on image content displayed on the target display.

12. A method according to claim 10 comprising controlling a luminance to which the predetermined image value is mapped based at least in part on an estimate of a general brightness adaptation.

13. A method according to claim 10 comprising controlling mid-range contrast based at least in part on an estimate of lateral brightness adaptation

14. A method according to claim 10 comprising controlling contrast in highlight and shadow regions based at least in part on an estimate of local brightness adaptation.

15. A method according to claim 2 wherein the target display has a greater peak luminance than the reference display and the mapping is configured to expand the luminance corresponding to image values corresponding to a highlight region above the mid-tone region.

16. A method according to claim 2 wherein the target display has a lower black level than the reference display and the mapping is configured to expand the luminance corresponding to image values corresponding to a shadow region below the mid-tone region.

20. A system configured to perform the method claim 1.

17. A method for encoding image data comprising:

processing image data to provide image values corresponding to quantized luminance steps wherein a step size between the quantized luminance steps is smaller in a highlight region than in a mid-tone region.

18. A method according to claim 17 wherein the mid-tone region includes at least luminance in the range of 1 to 10 nits.

19. A method according to claim 17 wherein the step size between the quantized luminance steps is smaller in a shadow region than in a mid-tone region.

21. An image capture device comprising:

a light-sensing array operable to detect light; and

a mapping unit connected to represent intensity of light sensed by elements of the light-sensing array as digital image values according to a response function;

and an exposure compensation mechanism connected to control the mapping unit such that a fixed point in the mid-range of the response function is made to correspond to a midpoint of the output image values.

22. An image capture device according to claim 21 wherein the exposure compensation mechanism is configured to adjust a mid-range contrast of the response function based on an exposure.

23. An image capture device according to claim 21 wherein the response function corresponds to a response curve having a mid-tone slope, a dark end slope and a bright end slope and the mid-range slope is smaller than either of the dark end slope and the bright end slope.