Colorization is a process to assign three dimensional color values to gray pixels, and this technique enables the conversion of black and white image and films into colored ones.1- 4 However the design of such a mapping is ambiguous in nature, and an interactive system was proposed in Ref. 1. In this approach, users are required to provide colors to some regions, and colors on the other regions are estimated by solving an optimization problem. Based on the same scenario, an algorithm using chrominance blending was proposed in Ref. 2. It shows similar or even better visual quality with less computations (see Fig. 1 to see the input and the output of this scenario). However, color bleeding is sometimes observed in these approaches probably due to the lack of global considerations. In other words, conventional approaches1- 3 are based on the assumption of locality, which can be summarized as “homogeneity of luminance indicates homogeneity of chrominance.” Therefore they have difficulties in handling points distant from scribbles, and the users need to provide a sufficient number of scribbles not only to detailed regions but also to relatively homogeneous regions in order to prevent color bleeding.