Full-color visibility model using CSF which varies spatially with local luminance
The present disclosure relate generally to image signal processing, color science and signal encoding. Signal encoding can be applied to color image data through use of a luminance contrast sensitivity function and a chrominance contrast sensitive function. Of course, other features, combinations and claims are disclosed as well.
1. An apparatus comprising:
memory storing: i) a luminance contrast sensitivity function (CSF 1 ), ii) a chrominance contrast sensitivity function (CSF 2 ), and iii) data representing color imagery;
means for estimating degradation of image areas associated with an application of signal encoding in the data representing color imagery by applying the CSF 1 and the CSF 2 to the data representing color imagery, in which the CSF 1 varies depending on luminance values associated with local regions of the data representing color imagery, and in which the CSF 1 is used for processing luminance data and the CSF 2 is used for processing chrominance data; and
means for changing the data representing color imagery with signal encoding, in which the signal encoding is guided based on results obtained from said means for estimating including estimated degradation of image areas.
2. The apparatus of claim 1 in which the CSF 1 varies spatially.
3. The apparatus of claim 2 in which the CSF 2 varies spatially in terms of spatial width.
4. The apparatus of claim 1 in which the CSF 1 varies spatially in terms of spatial width.
5. The apparatus of claim 1 in which the means for estimating degradation produces image blurring as the estimated degradation, in which the CSF 1 varies so that relatively more blurring occurs as luminance of a local image region decreases.
6. The apparatus of claim 1 in which the means for changing utilizes results obtained from the means for estimating by varying signal encoding strength across different image areas of the data representing color imagery based on estimated degradation of the different image areas.
7. The apparatus of claim 6 in which estimated degradation of the signal encoding across the different image areas comprises uniform estimated degradation.
8. The apparatus of claim 1 further comprising means for applying an attention model to the data representing color imagery to predict visual traffic areas.
9. The apparatus of claim 8 in which the means for changing utilizes predicted visual traffic areas and the estimated degradation of image areas.
10. The apparatus of claim 1 in which the chrominance contrast sensitivity function (CSF 2 ) comprises a blue-yellow contrast sensitivity function and a red-green contrast sensitivity function.
11. The apparatus of claim 1 in which the CSF 2 varies depending on luminance values associated with local regions of the obtained color image data.
12. The apparatus of claim 1 in which said means for changing the data representing color imagery with signal encoding encodes a payload into the data representing color imagery.
13. The apparatus of claim 1 in which the color imagery comprises video.
14. A method comprising:
obtaining color image data;
changing the color image data with signal encoding, the signal encoding comprising a payload, said changing yielding encoded color image data;
comparing the encoded color image data to the color image data to determine a visibility map, the visibility map comprising a luminance contrast sensitivity function (CSF 1 ) and a chrominance contrast sensitivity function (CSF 2 );
weighting the signal encoding per the visibility map so that local image areas within the color image data are weighted differently, said weighting yielding weighted signal encoding;
encoding the color image data with the weighted signal encoding to yield locally varied encoded color image data.
15. The method of claim 14 in which the CSF 1 introduces image blurring, and in which the CSF 1 varies so that relatively more blurring occurs as luminance of a local image region decreases.
16. The method of claim 15 in which said weighting varies signal encoding strength across different local image regions of the color image data to yield uniform visibility of the signal encoding across the color image data.
17. The method of claim 16 in which the color image data represents video data.
18. The method of claim 14 in which the CSF 1 varies spatially in terms of spatial width.
19. The method of claim 14 in which the CSF 2 varies spatially in terms of spatial width.
20. The method of claim 14 in which the CSF 2 comprises a blue-yellow contrast sensitivity function and a red-green contrast sensitivity function.
21. A non-transitory computer readable medium comprising instructions, which when executed configure one or more processors to:
access color image data;
change the color image data with signal encoding, the signal encoding comprising a payload, said changing yielding encoded color image data;
compare the encoded color image data to the color image data to determine a visibility map, the visibility map comprising a luminance contrast sensitivity function (CSF 1 ) and a chrominance contrast sensitivity function (CSF 2 );
weight the signal encoding per the visibility map so that local image areas within the color image data are weighted differently to yield weighted signal encoding;
encode the color image data with the weighted signal encoding to yield locally varied encoded color image data.
22. The non-transitory computer readable medium of claim 21 in which the CSF 1 introduces image blurring, and in which the CSF 1 varies so that relatively more blurring occurs as luminance of a local image region decreases.
23. The non-transitory computer readable medium of claim 22 in which the signal encoding strength varies across different local image regions of the color image data to yield uniform visibility of the signal encoding across the color image data.
24. The non-transitory computer readable medium of claim 21 in which the CSF 1 varies spatially in terms of spatial width.
25. The non-transitory computer readable medium of claim 21 in which the CSF 2 varies spatially in terms of spatial width.
26. The non-transitory computer readable medium of claim 21 in which the CSF 2 comprises a blue-yellow contrast sensitivity function and a red-green contrast sensitivity function.
27. The non-transitory computer readable medium of claim 21 in which the color image data represents video data.