Method and apparatus for determining a gamut boundary and a gamut descriptor

An apparatus for creating and using a device gamut boundary descriptor, comprising:

• input means for reading a look-up table for translating a signal in a device dependent color space into a device independent color space;
• table means for creating a gamut boundary table including boundary triangles;
• selection means for selecting boundary triangles enclosing each of signals of a predetermined regularly spaced pattern of device independent space color signals, the selection means including means for slicing the gamut expressed in device independent space using parallel planes separated by a predetermined distance;
• means for selecting unit vectors in each plane separated by a predetermined angle;
• and
• means for determining the intersection point signal of each unit vector and the gamut boundary and generating a signal representing the intersection point by:
• (i) defining a convex polyhedral cone using points on the gamut boundary;
• (ii) finding a polyhedral cone enclosing each unit vector;
• (iii) determining the convex cone coefficients;
• and
• (iv) determining the intersection point signal using the coefficients;
• interpolation means for performing a triangle interpolation for each device independent color signal creating a gamut boundary descriptor list;
• storage means for storing the gamut boundary descriptor list for determining whether a color signal is within a gamut;
• means for selecting a test point along the unit vector;
• means for comparing the test point to the intersection point with a result of the comparison indicating whether the test point is in the gamut;
• and
• means for identifying the colors falling outside the gamut descriptor to within the reproducible gamut of the device and processing these colors for display.