Fast contour tracing algorithm

A simple and fast algorithm for contour tracing in two-level BitMap image is presented. The common comer of four neighbouring pixels, NODE, is defined as the basic element of the analysed structure. First the image is convoluted with 2*2 kernel which identifies all nodes, then the algorithm follows the line connecting contour nodes, and extracts coordinates of border pixels according to the initial conditions, i.e., to the defined connectivity type and contour rotation. The main parts of this procedure (written in C/sup ++/) and results obtained with the demonstration program KRATA, based on this algorithm, are presented.