Methods and apparatus for converting color values
View Patent ↗Color conversion apparatus and methods are provided for converting a first color value, such as an RGB, L*a*b* or XYZ color value, to a second color value, such as an RGB, CMY, CMKY, L*a*b*, L, C 1 C 2 , or XYZ color value, without saturation error.
1. A color conversion system comprising:
a color converter comprising a plurality of inputs for receiving first color values, and a plurality of outputs for providing intermediate color values, the color converter comprising a modified color conversion lookup table that is created by:
receiving a color conversion lookup table that includes a plurality of table entries, each entry associating a corresponding first value to a corresponding second value;
identifying a minimum value of the plurality of corresponding second values;
identifying table entries that have corresponding second values equal to the minimum value, and that are adjacent an entry having a corresponding second value greater than the minimum value;
compressing the corresponding second value of each of the table entries to form corresponding intermediate values; and
replacing the corresponding intermediate value of each of the identified entries with a value determined by a regression that includes the corresponding intermediate value of the corresponding adjacent entry.
2. The system of claim 1 , wherein each of the corresponding second values has a first bit-length, and the method further comprises converting the corresponding second values to values having a second bit length.
3. The system of claim 2 , wherein the second bit length is greater than the first bit length.
4. The system of claim 1 , wherein compressing comprises linearly compressing the corresponding second value of each of the table entries.
5. The system of claim 1 , wherein compressing comprises multiplying the corresponding second value of each of the table entries by a scale factor.
6. The system of claim 1 , wherein compressing comprises adding a constant value to the corresponding second value of each of the table entries.
7. The system of claim 1 , wherein the regression comprises linear extrapolation.
8. A color conversion system comprising:
a color converter comprising a plurality of inputs for receiving first color values, and a plurality of outputs for providing intermediate color values, the color converter comprising a modified color conversion lookup table that is created by:
receiving a color conversion lookup table that includes a plurality of table entries, each entry associating a corresponding first value to a corresponding second value;
identifying a maximum value of the plurality of corresponding second values;
identifying table entries that have corresponding second values equal to the maximum value, and that are adjacent an entry having a corresponding second value less than the maximum value;
compressing the corresponding second value of each of the table entries to form corresponding intermediate values; and
replacing the corresponding intermediate value of each of the identified entries with a value determined by a regression that includes the corresponding intermediate value of the corresponding adjacent entry.
9. The system of claim 8 , wherein each of the corresponding second values has a first bit-length, and the method further comprises converting the corresponding second values to values having a second bit length.
10. The system of claim 9 , wherein the second bit length is greater than the first bit length.
11. The system of claim 8 , wherein compressing comprises linearly compressing the corresponding second value of each of the table entries.
12. The system of claim 8 , wherein compressing comprises multiplying the corresponding second value of each of the table entries by a scale factor.
13. The system of claim 8 , wherein compressing comprises adding a constant value to the corresponding second value of each of the table entries.
14. The system of claim 8 , wherein the regression comprises linear extrapolation.
15. A computer readable medium comprising computer program instructions structured to cause a computer to modify a color conversion lookup table that includes a plurality of table entries, each entry associating a corresponding first value to a corresponding second value, the instructions causing the machine to:
identify a minimum value of the plurality of corresponding second values;
identify table entries that have corresponding second values equal to the minimum value, and that are adjacent an entry having a corresponding second value greater than the minimum value;
compress the corresponding second value of each of the table entries to form corresponding intermediate values; and
replace the corresponding intermediate value of each of the identified entries with a value determined by a regression that includes the corresponding intermediate value of the corresponding adjacent entry.
16. The computer readable medium of claim 15 , wherein each of the corresponding second values has a first bit-length, and the instructions further cause the machine to convert the corresponding second values to values having a second bit length.
17. The computer readable medium of claim 16 , wherein the second bit length is greater than the first bit length.
18. The computer readable medium of claim 15 , wherein the instructions further cause the machine to linearly compress the corresponding second value of each of the table entries.
19. The computer readable medium of claim 15 , wherein the instructions further cause the machine to multiply the corresponding second value of each of the table entries by a scale factor.
20. The computer readable medium of claim 15 , wherein the instructions further cause the machine to add a constant value to the corresponding second value of each of the table entries.
21. The computer readable medium of claim 15 , wherein the regression comprises linear extrapolation.
22. A computer readable medium comprising computer program instructions structured to cause a computer to modify a color conversion lookup table that includes a plurality of table entries, each entry associating a corresponding first value to a corresponding second value, the instructions causing the machine to:
identify maximum value of the plurality of corresponding second values;
identify table entries that have corresponding second values equal to the maximum value, and that are adjacent an entry having a corresponding second value less than the maximum value;
compress the corresponding second value of each of the table entries to form corresponding intermediate values; and
replace the corresponding intermediate value of each of the identified entries with a value determined by a regression that includes the corresponding intermediate value of the corresponding adjacent entry.
23. The computer readable medium of claim 22 , wherein each of the corresponding second values has a first bit-length, and the instructions further cause the machine to convert the corresponding second values to values having a second bit length.
24. The computer readable medium of claim 23 , wherein the second bit length is greater than the first bit length.
25. The computer readable medium of claim 22 , wherein the instructions further cause the machine to linearly compress the corresponding second value of each of the table entries.
26. The computer readable medium of claim 22 , wherein the instructions further cause the machine to multiply the corresponding second value of each of the table entries by a scale factor.
27. The computer readable medium of claim 22 , wherein the instructions further cause the machine to add a constant value to the corresponding second value of each of the table entries.
28. The computer readable medium of claim 22 , wherein the regression comprises linear extrapolation.