Patent ID: 7123380

Claim:
A method for determining a set of M color gamut parts of a color reproduction process that uses N inks (N>3), M and N being integers, said color reproduction process having a device independent color space having a first, a second and a third dimension corresponding with first, second and third magnitudes respectively, the method comprising the steps of: determining a set of M umbrella surface parts in said device independent color space, each surface part obtained by the following steps: defining a domain corresponding to a range of a first ink in combination with a range of a second ink; identifying a point belonging to said domain having a first amount for said first ink and a second amount for said second ink; setting a third ink to a predetermined minimum amount and determining a first magnitude corresponding to said first dimension of a color of said first amount of said first ink in combination with said second amount of said second ink in combination with said minimum amount of said third ink; setting said third ink to a predetermined maximum amount and determining a second magnitude corresponding to said first dimension of the color of said first amount of said first ink in combination with said second amount of said second ink in combination with said maximum amount of said third ink; defining an umbrella surface part as a locus of colors in said device independence color space corresponding to said domain in combination with said third ink that yields a highest of said first and said second magnitudes corresponding to said first dimension of said device independent color space; identifying for each of said set surface parts at least one darkening ink that is different from said first, second and third inks; and developing each one of a set of M umbrella surface parts into a color gamut volume part by varying said at least one darkening ink in combination with varying said amount of said first ink and varying said amount of said second ink over said domain.