Abstract
In fractal block coding technique, an image is divided into blocks and codes of the image are made by searching similar blocks. Chotic images that are not suitable for conventional compression techniques are processed at high compression rate by using fractal coding. However, this technique is too time consuming to use practically. This paper proposes a method to improve the processing time.Because it is necessary that no perceptible defect generates in the reconstructed image, the ability of the visual sense is considered in the algorithm. Edge information extracted by using a ▽^2G filter is used to make a quadtree that represents a variable block division of the image. However, edge blocks are divided into the smallest blocks because edge blocks are important to the visual sense. Similar blocks are searched adaptively on this variable block structure. Moreover, flat blocks are searched in the permitted error by using the established threshold.This method achieves the 1/2.75 reduction in processing time and the 1/1.29 reduction in compression rate. The S/N ratio is 0.7 dB worse, but the degradation is not noticeable.
