Contour chain-coding and topological hierarchy analysis in a 2×3 window single-pass raster scan

This paper presents a fast and effective method for generating chain-encoded representations of arbitrary contours of connected regions in a binary image. Furthermore, an optional method is presented allowing the additional concurrent extraction of the topological hierarchy tree within the image. Both parts of the algorithm are executed by means of a single raster scan with a 2×3 neighborhood convolution window. This not only allows the reduction of the pixel buffer to a single image line, it furthermore enables fast neighborhood evaluation by means of a moderately sized look-up-table with 64 entries, to be directly addressed by the six pixel in window focus. With these main characteristics, the algorithm is well suited for efficient parallel processing implementations in streaming applications.