Color Gamut Characterization Via Ray Tracing for Device Profile Generation

Color gamut characterization is an essential step in the ICC profile generation for imaging devices. It is also needed as part of evaluation and comparison of image quality achievable by different imaging systems. A novel technique is presented for characterizing the color gamut of an imaging device via ray tracing in the CIELAB color space. Initially, the convex hull of the set of measurement points is computed in the device space. Each of the resulting simplices in the convex hull structure has a set of CIELAB data triples associated with its vertices. The "local" convex hull is computed for each of those sets separately in CIELAB. The convex hull triangles are then subjected to a ray tracing procedure aimed at approximating the maximum achievable chroma for a set of pairs of L and hue angle values. For the purpose of the device profile generation, this set is derived from the set of grid points in the PCS (profile connection space) that have to be mapped to the device space. It is shown that the new method characterizes the gamut surface and volume better than the conventional technique based on computing the "global" convex hull of the measurement data points in CIELAB.