An Efficient Algorithm of Thinning Scanned Pencil Drawings
一种快速的扫描铅笔稿图细化算法

In computer aided 2D cartoon producing systems, the vectorization of scanned pencil drawings can greatly enhance the efficiency of inking and painting, retrieve lines and closures contained in the drawings and therefore lay the basis for implementation of more advanced functions such as autocoloring, inbetweening and so on. Thinning of scanned pencil drawings is the first step of the vectorization process. Having investigated and compared a lot of thinning algorithms, an improved noniterative thinning algorithm based on the idea of line following is presented. The improved algorithm is very efficient, which, requiring only one pass of image scanning and two passes of contour tracing, meets the high efficiency standard in computer aided 2D cartoon producing systems. Time complexity of the algorithm is analyzed in detail, and the method to reduce two kinds of image noises and to delete redundant branches after thinning are given.