Approximate coding of digital contours

Abstract

Two methods are proposed for coding the discrete contour of binary images. A set of key pixels (guiding pixels) on the contour is defined for this purpose. The decoding schemes approximate the contour through the key pixels using the quadratic Bezier approximation technique. The amount of deviation of the decoded image from the original image is studied using the objective measures of percentage error and shape compactness. The decoded images are found to be faithful reproductions of the original image. A set of cleaning operations is also introduced as an intermediate step before final reproduction. It was found that the bit requirements and the compression ratios are also improved significantly as compared to the contour run length coding and discrete line segment coding techniques.