A Fast Algorithm for Inverse Colormap Computation

The inverse colormap operation is the process which allows an image to be displayed with a limited set of colors. In order to obtain a minimal visual distortion between the input image annd the one displayed, inverse colormap algorithms associate each color with its nearest representative. The method presented in this paper is carried out in two steps. First, the 3D Voronoi diagram implicitly used by inverse colormap algorithms is approximated using a Karhunen-Loève transformation. Then, a correcting step is carried out in order to reduce the in uence of the first approximation. The complexity of our algorithm is independent of the size of the colormap. Moreover, its results are equal or quite close to the optimal solution.