Patent ID: 7529005
Filing Date: 2009-05-05
Classification: H04N

Abstract:
1. A method for processing a digital multi-colour image for reproduction thereof on a complementary colour image reproduction system provided with a plurality of process colours defining a gamut, the method comprising the steps of: dividing the gamut into a plurality of sub-gamuts, each sub-gamut being defined by three chromatic process colours of the plurality of process colours, such that at least one sub-gamut of the plurality of sub-gamuts comprises complementary process colours; selecting two complementary process colours, determining for each sub-gamut comprising the selected complementary process colours an associated first lightness value, which is the maximum of the lightness differences between the respective chromatic process colours defining the sub-gamut, ordering all sub-gamuts comprising the selected complementary process colours according to increasing first lightness value, and based on this lightness order associating each of the respective chromatic process colours with a single one of three different screens; determining for each sub-gamut of the plurality of sub-gamuts an associated second lightness value, which is the lightness difference in a predetermined colour space between the two chromatic process colours of the sub-gamut defining a plane positioned closest to the lightness axis; and determining for each pixel of the digital multi-colour image the sub-gamuts which can be used for rendering the corresponding pixel, selecting a sub-gamut with the lowest associated second lightness value among the determined sub-gamuts, and rendering the pixel with at most three chromatic process colours of the three chromatic process colours defining the selected sub-gamut, wherein each step is performed using a colour processing module of the colour image reproduction system.