Example Based Colorization Using Optimization

In this paper, we present an example-based colorization method to colorize a gray image. Besides the gray target image, the user only needs to provide a reference color image which is semantically similar to the gray image. We first segment both the target image and reference image and find correspondences at the segmentation level between these two images. The use of segmentation level can not only speed up the colorization process, but also obtain higher probability to maintain spatial coherence while doing color transfer than using independent pixel directly. Then for corresponding segments we apply pixel-wise chromatic value transfer from reference color image to target image only to the pixels with high confidence. And we use an optimization method [Levin et al. 2004] to propagate those sparse colors to the entire image. The features we use to measure the pixel confidence enable our method work well in both random scene images and images with obvious foreground and background structure. Finally, experimental results and user study on a large set of images demonstrate that our colorization method is competitive with previous state-of-the-art methods. CR Categories: I.3.3 [Computer Graphics]: Three-Dimensional Graphics and Realism—Display Algorithms I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism—Radiosity;