Color matching accuracy inside and outside the gamut

An apparatus for improving accuracy of a transformation implemented by a look-up table that maps colors from a first color space to a second color space for a color image reproduction system comprising an input device and an output device, said apparatus comprises components that:

• construct said look-up table, wherein the entries of said look-up table represent grid points that are derived by interpolation from a relatively small number of non-uniformly spaced points in said first color space,
• receive an identification of a region of said second color space in which the accuracy of said transformation is to be improved, said region being less than said second color space,
• obtain a medium conveying a selected color within said region of second color space,
• scan said medium with said input device to obtain first values representing said selected color in said first color space,
• apply said transformation to map said first values to second values in said second color space and determine a transformation error for said map, and
• modify one or more entries in said look-up table adjacent to said selected color, without increasing the number of entries in said look-up table and without changing the structure of said look-up table, to effect a change in said transformation so as to reduce said transformation error.

A medium readable by a machine embodying a program of instructions for execution by said machine to perform a method for improving accuracy of a transformation implemented by a look-up table that maps colors from a first color space to a second color space for a color image reproduction system comprising an input device and an output device, said method comprises:

• constructing said look-up table, wherein the entries of said look-up table represent grid points that are derived by interpolation from a relatively small number of non-uniformly spaced points in said first color space,
• receiving an identification of a region of said second color space in which the accuracy of said transformation is to be improved, said region being less than said second color space,
• obtaining a medium conveying a selected color within said region of second color space,
• scanning said medium with said input device to obtain first values representing said selected color in said first color space,
• applying said transformation to map said first values to second values in said second color space and determining a transformation error for said map, and
• modifying one or more entries in said look-up table adjacent to said selected color, without increasing the number of entries in said look-up table and without changing the structure of said look-up table, to effect a change in said transformation so as to reduce said transformation error.

An apparatus for improving accuracy of a transformation implemented by a look-up table that maps colors from a first color space to a second color space for a color image reproduction system comprising an input device and an output device, said apparatus comprises:

• a look-up table constructor to construct said look-up table, wherein the entries of said look-up table represent grid points that are derived bv interpolation from a relatively small number of non-uniformly spaced points in said first color space,
• a receiver to receive an identification of a region of said second color space in which the accuracy of said transformation is to be improved, said region being less than said second color space,
• an input unit to input a medium in said input device to obtain first values representing a selected color in said first color space,
• a mapper to apply said transformation to map said first values to second values in said second color space and determine a transformation error for said map, and
• a modifier to modify at least one entry in said look-up table adjacent to said selected color, without increasing the number of entries in said look-up table and without changing the structure of said look-up table, to effect a change in said transformation so as to reduce said transformation error.