Colorization of grayscale image is in general an active and challenging area of research in image processing.In this paper

current colorization algorithms are summarized and the principle of color propagation is analyzed.Then a colorization algorithm based on Laplace equation is proposed.In order to determine the boundary accurately

a weighted difference scheme is applied.In contrast with Saprio's colorization algorithm which is also a partial differential equation based method

the principle of color propagation in our algorithm is different.Furthermore

our algorithm can achieve more vivid colorized result.