초록 ▼

Some embodiments of the invention provide a method for mapping a source color into a color gamut without changing the value of its hue attribute. In some embodiments, a source color is initially represented by a first set of color coordinates that are defined with respect to a first coordinate syste

Some embodiments of the invention provide a method for mapping a source color into a color gamut without changing the value of its hue attribute. In some embodiments, a source color is initially represented by a first set of color coordinates that are defined with respect to a first coordinate system. The first set of color coordinates is then transformed to a second set of color coordinates, defined in a second coordinate system. If the second set of color coordinates is outside of a selected color gamut, the value of a first color coordinate of the second set of color coordinates is reduced until the second set of color coordinates is in-gamut. The first coordinate axis of the second coordinate system is either an “R” axis or a coordinate axis that is independent of hue, “H”, and not identical to chroma, C*. The in-gamut set of color coordinates comprises a gamut-mapped color corresponding to the source color.

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1. A method of mapping color coordinates defined in a first coordinate system into a first color gamut defined in a second coordinate system, wherein said second coordinate system comprises a spherical coordinate system including an “R” axis having luminosity and chroma parameters, a &

1. A method of mapping color coordinates defined in a first coordinate system into a first color gamut defined in a second coordinate system, wherein said second coordinate system comprises a spherical coordinate system including an “R” axis having luminosity and chroma parameters, a “T” axis having luminosity and chroma parameters, and an “H” axis having a hue parameter, said method comprising:a) selecting a first set of color coordinates defined in the first coordinate system;b) generating a second set of color coordinates defined in the second coordinate system, from the first set of color coordinates; andc) if the second set of color coordinates is outside of the color gamut, reducing an “R” axis color coordinate of said second set of color coordinates so as to generate a first set of gamut-mapped color coordinates inside said color gamut. 2. A method according to claim 1 further comprising:d) if said second set of color coordinates is in said color gamut, one of not changing said “R” axis color coordinate of said second set of color coordinates and changing said “R” axis color coordinate of said second set of color coordinates so as to form a first set of gamut-mapped color coordinates that remain in said color gamut. 3. A method according to claim 1 further comprising:e) generating a second set of gamut-mapped color coordinates defined in the first coordinate system, from the first set of gamut-mapped color coordinates. 4. A method according to claim 1 wherein determining whether said second set of color coordinates is outside of said first color gamut comprises:locating a point on a boundary of said first color gamut having an “H” axis color coordinate and a “T” axis color coordinate equal to an “H” axis color coordinate and a “T” axis color coordinate of said second set of color coordinates;if an “R” axis color coordinate of said second set of color coordinates is greater than an “R” axis color coordinate of said point on said boundary of said color gamut, determining that said second set of color coordinates is out of said color gamut; andif an “R” axis color coordinate of said second set of color coordinates is not greater than an “R” axis color coordinate of said point on said boundary of said color gamut, determining that said second set of color coordinates is in said color gamut. 5. A method according to claim 1 wherein prior to said generating a second set of color coordinates the method further comprises:selecting and defining said first color gamut in said first coordinate system. 6. A method according to claim 1 wherein prior to said generating a second set of color coordinates the method further comprises:selecting a set of color coordinates in first coordinate system, of an origin of said second coordinate system. 7. A method according to claim 6 wherein said origin of said second coordinate system is selected according to at least one of said first set of color coordinates and sets of color coordinates in said first color gamut defined in said first coordinate system. 8. A method according to claim 7 wherein said origin of said second coordinate system is selected according to a look-up table of said first set of color coordinates. 9. A method according to claim 6 further comprising:repeating said mapping color coordinates for a plurality of sets of color coordinates defined in the first coordinate system. 10. A method according to claim 9 wherein the origin of said second coordinate system selected for mapping said first set of color coordinates defined in the first coordinate system has different color coordinates in said first coordinate system than does an origin of a second coordinate system selected for mapping a third set of color coordinates defined in the first coordinate system. 11. A method according t o claim 9 wherein said plurality of sets of color coordinates defined in the first coordinate system comprises a second color gamut and said mapping color coordinates comprises mapping the sets of color coordinates of said second color gamut into said first color gamut. 12. A method according to claim 11 wherein each set of color coordinates contained in a boundary of said second color gamut is mapped to a set of color coordinates contained in a boundary of said first color gamut. 13. A method according to claim 1 wherein said first coordinate system is one of an “RGB” coordinate system, a “CMY” coordinate system, an “CIELAB” coordinate system, another rectangular coordinate system, and an “LCH” cylindrical coordinate system. 14. A method according to claim 1 wherein said generating a second set of color coordinates comprises:transforming from a rectangular “CIELAB” coordinate system comprising:an L* axis including a lightness parameter;an a* axis including a redness and greenness parameter; anda b* axis including a yellowness and blueness parameter; andtransforming to a spherical “RTH” coordinate system comprising:an “R” axis including chroma and luminosity parameters according to the equation R ”=(( L*−c 1 ) 2 +( a*−c 2 ) 2 +( b*−c 3 ) 2 );where c 1 +c 2 +c 3 are the arctan and in this case 50, 0, 0an “H” axis including a hue parameter according to the equation H ”=arctan( b*/a *); anda “T” axis including chroma and luminosity parameters according to the equation T ”=arccos( L*/“R ”). 15. A method of mapping color coordinates defined in a first coordinate system into a first color gamut defined in a second coordinate system, wherein said second coordinate system includes a first axis including luminosity and chroma parameters, wherein the first axis is independent of a hue axis and is not identical to a chroma axis, a second axis having luminosity and chroma parameters, and a third axis having a hue parameter, said method comprising:a) selecting a first set of color coordinates defined in the first coordinate system;b) generating a second set of color coordinates defined in the second coordinate system, from the first set of color coordinates; andc) if the second set of color coordinates is outside of the color gamut, reducing a first axis color coordinate of said second set of color coordinates so as to generate a first set of gamut-mapped color coordinates inside said color gamut. 16. A method according to claim 15 further comprising:d) if said second set of color coordinates is in said color gamut, one of not changing said first axis color coordinate of said second set of color coordinates and changing said first axis color coordinate of said second set of color coordinates so as to form a first set of gamut-mapped color coordinates that remain in said color gamut. 17. A method according to claim 15 further comprising:e) generating a second set of gamut-mapped color coordinates defined in the first coordinate system, from the first set of gamut-mapped color coordinates. 18. A method according to claim 15 wherein determining whether said second set of color coordinates is outside of said first color gamut comprises:locating a point on a boundary of said first color gamut having a second axis color coordinate and a third axis color coordinate equal to a second axis color coordinate and a third axis color coordinate of said second set of color coordinates;if a first axis color coordinate of said second set of color coordinates is greater than a first axis color coordinate of said point on said boundary of said color gamut, determining that said second set of color coordinates is out of said color gamut; andif a first axis color coordinate of said second set of color coordinates is not greater than a first axis color coordinate of said point on said boundary of said color gamut, determining that said second set of color coordinates is in said color gamut. 19. A method according to claim 15 wherein prior to said generating a second set of color coordinates the method further comprises:selecting and defining said first color gamut in said first coordinate system. 20. A method according to claim 15 wherein prior to said generating a second set of color coordinates the method further comprises:selecting said second coordinate system; andselecting a set of color coordinates in first coordinate system, of an origin of said second coordinate system. 21. A method according to claim 20 wherein at least one of said second coordinate system and said origin of said second coordinate system is selected according to at least one of said first set of color coordinates and sets of color coordinates in said first color gamut defined in said first coordinate system. 22. A method according to claim 21 wherein at least one of said second coordinate system and said origin of said second coordinate system is selected according to a look-up table of said first set of color coordinates. 23. A method according to claim 20 further comprising:repeating said mapping color coordinates for a plurality of sets of color coordinates defined in the first coordinate system. 24. A method according to claim 23 wherein the origin of said second coordinate system selected for mapping said first set of color coordinates defined in the first coordinate system has different color coordinates in said first coordinate system than does an origin of a second coordinate system selected for mapping a third set of color coordinates defined in the first coordinate system. 25. A method according to claim 24 wherein said second coordinate system selected for mapping said first set of color coordinates defined in the first coordinate system has different axes than does a second coordinate system selected for mapping a third set of color coordinates defined in the first coordinate system. 26. A method according to claim 25 wherein at least two of an “R” axis, a chroma axis, a lightness axis, and another hue independent axis comprise a first axis of a second coordinate system for at least one of said plurality of sets of color coordinates defined in the first coordinate system. 27. A method according to claim 23 wherein said plurality of sets of color coordinates defined in the first coordinate system comprises a second color gamut and said mapping color coordinates comprises mapping the sets of color coordinates of said second color gamut into said first color gamut. 28. A method according to claim 27 wherein each set of color coordinates contained in a boundary of said second color gamut is mapped to a set of color coordinates contained in a boundary of said first color gamut. 29. A method according to claim 15 wherein said first coordinate system is one of an “RGB” coordinate system, a “CMY” coordinate system, an “CIELAB” coordinate system, another rectangular coordinate system, and an “LCH” cylindrical coordinate system. 30. A method according to claim 15 wherein said generating a second set of color coordinates comprises:transforming from a rectangular “CIELAB” coordinate system comprising:an L* axis including a luminosity parameter;an a* axis including a redness and greenness parameter; anda b* axis including a yellowness and blueness parameter; andtransforming to a spherical “RTH” coordinate system comprising:an “R” axis including chroma and luminosity parameters according to the equation R ”=( L*−c 1 ) 2 +( a*−c 2 ) 2 +( b*−c 3 ) 2 );where c 1 +c 2 =c 3 are the arctan and in this case 50, 0, 0an “H” axis including a hue parameter according to the equation H ”=arctan( b*/a *); anda “T” axis including chroma and luminosity parameters according to the equation T ”=arcos( L*/“R ”). 31. A computer readable storage medium on which is embedded one or more computer programs, said one or more computer programs implementing a method for mapping color coordinates defined in a first coordinate system into a first color gamut defined in a second coordinate system, wherein said second coordinate system comprises a spherical coordinate system including an “R” axis having luminosity and chroma parameters, a “T” axis having luminosity and chroma parameters, and an “H” axis having a hue parameter, said one or more computer programs comprising a set of instructions for:a) selecting a first set of color coordinates defined in the first coordinate system;b) generating a second set of color coordinates defined in the second coordinate system, from the first set of color coordinates; andc) if the second set of color coordinates is outside of the color gamut, reducing an “R” axis color coordinate of said second set of color coordinates so as to generate a first set of gamut-mapped color coordinates inside said color gamut. 32. The computer readable storage medium according to claim 31, said one or more computer programs further comprising a set of instructions for:transforming from a rectangular “CIELAB” coordinate system comprising:an L* axis including a lightness parameter;an a* axis including a redness and greenness parameter; anda b* axis including a yellowness and blueness parameter; andtransforming to a spherical “RTH” coordinate system comprising:an “R” axis including chroma and luminosity parameters according to the equation R ”=(( L*−c 1 ) 2 +( a*−c 2 ) 2 +( b*−c 3 ) 2 );where c 1 +c 2 +c 3 are the arctan and in this case 50, 0, 0an “H” axis including a hue parameter according to the equation H ”=arctan( b*/a *); anda “T” axis including chroma and luminosity parameters according to the equation T ”=arccos( L*/“R ”).