Video enhancement and display power management

Abstract

In visual display devices such as LCD devices with backlight illumination, the backlight typically consumes most of device battery power. In the interest of displaying a given pixel pattern at a minimized backlight level, the pattern can be transformed while maintaining image quality, with a transform determined from pixel luminance statistics. Aside from, or in addition to such minimizing, a transform also can be used for image enhancement, for a displayed image better to meet a visual perception quality. In either case, the transform preferably is constrained for enforcing one or several display attributes.

Description

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a graph showing an exemplary pixel value distribution along a line of 256 pixel values as may arise for a particular given pattern, and further showing the graphs of the identity transform and of an illustrative multi-stage transform.

FIG. 2 is a graph showing the pixel value distribution of FIG. 1 approximated by a step function, and further showing how the transform slopes are computed.

FIG. 3 is a graph showing a multi-stage transform obtained for the step function of FIG. 2.

FIG. 4 is a representation of an exemplary procedure for transforming the given pixel values using the pixel value distribution of the given pattern in accordance with a preferred embodiment of the invention.

FIG. 5 is a representation of a further exemplary procedure for transforming the given pixel values using the pixel value distribution of the given pattern, representing a further preferred embodiment of the invention.

FIG. 6 is a block schematic of an exemplary embodiment of the technique.

Claims

1. A computer method for generating a pixel display pattern from a pixel given pattern using a transform, the method comprising: (a) for at least one display attribute, determining at least one constraint on the transform; and(b) for at least one substantially uniform background luminance value and subject to the at least one constraint, determining the transform such that, if the pixel display pattern is displayed against the substantially uniform background, visual distortion as compared with the pixel given pattern is minimized.

2. The method of claim 1, wherein the at least one constraint is for minimizing washout in a generated pixel-display-pattern image.

3. The method of claim 1, wherein the at least one constraint is for maintaining contrast in a generated pixel-display-pattern image.

4. The method of claim 1, wherein the transform is determined from statistics of pixel-luminance-given values of the pixel given pattern.

5. The method of claim 4, wherein the statistics comprises histogram information.

6. The method of claim 1, wherein the substantially uniform background luminance value is prescribed.

7. The method of claim 1, wherein the substantially uniform background luminance value is determined by information obtained from pixel-luminance-given values of the pixel given pattern.

8. The method of claim 7, wherein the information is obtained from a histogram of the pixel-luminance-given values.

9. The method of claim 1, further comprising determining a minimized background luminance value.

10. The method of claim 9, wherein determining the minimized background luminance value comprises using statistics of pixel-given-luminance values of the pixel given pattern.

11. The method of claim 9, wherein step 1.(b) is performed for a plurality of different background luminance values.

12. The method of claim 1, wherein the transform comprises a piecewise linear function.

13. The method of claim 12, wherein each of the linear pieces of the piecewise linear function spans at least one bin of a histogram of pixel-luminance-given values of the pixel given pattern

14. The method of claim 13, wherein at least one of the linear pieces of the piecewise linear function has a slope which is determined from: local statistics of the pixel-luminance-given values in a histogram bin spanned by the at least one of the linear pieces, andglobal statistics over all histogram bins.

15. The method of claim 12, wherein the at least one constraint comprises a constraint on a slope of a linear piece of the piecewise linear function.

16. The method of claim 15, wherein, at contiguous low pixel luminance values of the pixel given pattern, the slope is fixed.

17. The method of claim 15, wherein, at contiguous high pixel luminance values of the pixel given pattern, the slope is fixed.

18. The method of claim 1, further comprising spatial high-pass filtering of the pixel display pattern.

19. The method of claim 1, wherein the pixel given pattern is one of a video sequence.

20. The method of claim 19, further comprising temporal low-pass filtering of sequential transformed display patterns.

21. The method of claim 1, wherein the pixel given pattern has chrominance, and the method further comprises determining a factor for scaling the chrominance.

22. The method of claim 1 applied to a plurality of pixel given patterns of a video sequence to generate different uniform background luminance values for respective pixel display patterns.

23. The method of claim 1, further comprising accepting input of: pixel-luminance-given values of the pixel given pattern, and at least one of: (i) video sequence history, (ii) LCD panel characteristics and (iii) ambient light condition.

24. The method of claim 1, further comprising transmitting the pixel display pattern for display on a display device.

25. The method of claim 24, further comprising transmitting the substantially uniform background luminance value to the display device.

26. The method of claim 25, further comprising displaying the pixel display pattern against a background having the substantially uniform background luminance.

27. The method of claim 24, further comprising displaying the pixel display pattern against a background other than the background having the substantially uniform background luminance.

28. The method of claim 24, wherein the display device is included in one of: a notebook-PC, a DVD playback device, a handheld consumer electronic device, a portable media player, a PDA device, an LCD TV and a mobile phone.

29. A device for generating a pixel display pattern from a pixel given pattern using a transform, the device comprising: (a) a first device portion which, for at least one display attribute, is made for determining at least one constraint on the transform; and(b) a second device portion which, for at least one substantially uniform background luminance value and subject to the at least one constraint, is made for determining the transform such that, if the pixel display pattern is displayed against the substantially uniform background, visual distortion as compared with the pixel given pattern is minimized.

30. A processor for generating a pixel display pattern from a pixel given pattern using a transform, the processor comprising: (a) a first processor module which, for at least one display attribute, is instructed for determining at least one constraint on the transform; and(b) a second processor module which, for at least one substantially uniform background luminance value and subject to the at least one constraint, is instructed for determining the transform such that, if the pixel display pattern is displayed against the substantially uniform background, visual distortion as compared with the pixel given pattern is minimized.

31. A service for generating a pixel display pattern from a pixel given pattern using a transform, the service comprising: (a) a first service element which, for at least one display attribute, is for determining at least one constraint on the transform; and(b) a second service element which, for at least one substantially uniform background luminance value and subject to the at least one constraint, is for determining the transform such that, if the pixel display pattern is displayed against the substantially uniform background, visual distortion as compared with the pixel given pattern is minimized.