Device-independent and medium-independent color matching between an input device and an output device

DETAILED DESCRIPTION What is claimed is: 1.
A method for deriving color space transformations for a color image reproduction system comprising an input device and an output device, wherein said output device has an output-device gamut including colors capable of being rendered by said output device, said method comprises: obtaining a first transformation for said input device that maps from colors within an input-device-dependent color space to colors within a first device-independent color space, and obtaining a normalization transformation that normalizes all color data information in said first device-independent color space with respect to a white point in a second device-independent color space, wherein x.
sub.
0,y.
sub.
0,z.
sub.
0 is the maximum value for the coordinates in said first device-independent color space and wherein said normalization transformation is obtained by varying the values of the x.
sub.
0,y.
sub.
0,z.
sub.
0 coordinates.
2.
A method according to claim 1 wherein said first transformation is obtained by a process that comprises: generating coordinate values for points in said input-device-dependent color space by scanning a medium conveying a plurality of first areas having different first color characteristics, obtaining coordinate values for points in said first device-independent color space representing said first color characteristics, defining a first initial transformation that maps from points in said first device-independent color space to corresponding points in said input-device-dependent color space, and deriving said first transformation from said first initial transformation such that, for a color within said output-device gamut, said first transformation is defined by interpolation of point values within said first device-independent color space, and for a first color outside of said output-device gamut, said first transformation is defined by a point in said first device-independent color space that corresponds to an intersection of a boundary of said output-device gamut with a projection between a point representing said first color and a neutral-color line