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.