Color converting device emphasizing a contrast of output color data corresponding to a black character

A color converting device converting an input color signal composed of n color signals into an output color signal by dividing an n-dimensional input color space into a plurality of polyhedral units, dividing each of said polyhedral units into a plurality of solids, and performing an interpolative calculation using interpolation coefficients corresponding to one of said solids to which said input color signal belongs, where n is a natural number not smaller than 4, the device comprising:

• storing means for storing n-dimensional interpolation coefficients corresponding to each of said solids;
• determining means for dividing each of said n color signals into higher-order data and lower-order data, and determining which one of said solids of one of said polyhedral units said input color signal belongs to according to a magnitude relation among said lower-order data of said n color signals excluding at least one color signal therefrom, the one of said polyhedral units being selected according to said higher-order data;
• reading means for reading the n-dimensional interpolation coefficients corresponding to the determined one of said solids from said storing means;
• generating means for generating (n−1)-dimensional interpolation coefficients used for an (n−1)-dimensional interpolative calculation from said n-dimensional interpolation coefficients;
• and
• interpolating means for performing said (n−1)-dimensional interpolative calculation by using said lower-order data and said (n−1)-dimensional interpolation coefficients.

A color converting method for converting an input color signal into an output color signal by dividing a four-dimensional input color space into a plurality of 16-vertex units, and performing an interpolative calculation using interpolation coefficients corresponding to one of said 16-vertex units to which said input color signal belongs, the method comprising:

• the determining step of dividing said input color signal into higher-order data and lower-order data, dividing one of said 16-vertex units selected according to said higher-order data into six 8-vertex solids, and determining which one of said six 8-vertex solids said input color signal belongs to according to a magnitude relation among said lower-order data;
• the generating step of generating three-dimensional interpolation coefficients used for a three-dimensional interpolative calculation from four-dimensional interpolation coefficients corresponding to the determined one of said 8-vertex solids;
• and
• the interpolating step of performing said three-dimensional interpolative calculation by using said lower-order data and said three-dimensional interpolation coefficients so as to generate said output color signal.

A computer readable recording medium storing program code for causing a computer to convert an input color signal into an output color signal by dividing a four-dimensional input color space into a plurality of 16-vertex units, and performing an interpolative calculation using interpolation coefficients corresponding to one of said 16-vertex units to which said input color signal belongs, the recording medium comprising:

• determining program code means for dividing said input color signal into higher-order data and lower-order data, dividing one of said 16-vertex units selected according to said higher-order data into six 8-vertex solids, and determining which one of said six 8-vertex solids said input color signal belongs to according to a magnitude relation among said lower-order data;
• generating program code means for generating three-dimensional interpolation coefficients used for a three-dimensional interpolative calculation from four-dimensional interpolation coefficients corresponding to the determined one of said 8-vertex solids;
• and
• interpolating program code means for performing said three-dimensional interpolative calculation by using said lower-order data and said three-dimensional interpolation coefficients so as to generate said output color signal.