Colorization

It is a course project of Digital Image Processing

Due to its unique expression of details, Japanese comic is really a different but interesting topic on image processing. In this paper we provide a approach to colorize a black-and-white comic with different colors. As common cases, users need to strike on the figure to give a start of the colorization. We will consider a lot of factor to decide how to colorize a certain area. Also the algorithm automatically detect the existence of edge and preserve it from the color-spreading progress.

Related work

sample of traditional colorization algorithm:

[1] A. Levin, D. Lischinski, Y. Weiss, Colorization Using Optimization, ACM Transactions on Graphics, 2004.

[2] D. Sykora, J. Burianek, Jirizara, Unsupervised Ccolorization of Black-and-white Cartoons, Third International Symposium on Non Photorealistic Animation and Rendering, 2004.

Traditional algorithm failed to achieve a good performance in comic colorization since usually, they demand the figure to have a continuous luminance, while comic figure using dots and lines to represent changing grayscale.

sample of comic colorization algorithm:

[3]Yingge Qu, Tien-TsinWong, Pheng-Ann Heng, Manga Colorization, ACM Transactions on Graphics (SIGGRAPH 2006 issue), 2006

This work achieved a desirable performance but the time complexity is too large.

edge-preserving graph smoothing:

[4]Kartic Subr, Cyril Soler, Fredo Durand, Edge-preserving Multiscale Image Decompostion based on Local Extrema, Transactions on Graphics 2009.

This work decomposed a figure into several components and protect the edge information.

Our work

Our colorization approach is based on both [1] and [4]. The algorithm is composed of two step. First, we will use Delauney triangulation to divide the figure into small pieces and performing interpolation within each triangle. Secondly, colorization will be performed using Levin's approach. An sample is as following.

origin figure

colored figure