Hierarchical coding of binary images

On the reconstruction of quadtree data

Image compression schemes consist of compression and decompression phases. Often, the decompression phase includes mechanisms for improving the quality of the resulting image. Quadtree compression is one such type of compression. Reconstructed quadtree images can be blocky because of the nature of the compression method, unless additional processing, generally smoothing, is performed. We propose improvements over the reconstruction method described by Shusterman and Feder. The improvements consist of the introduction of a simpler and more effective 2 x 2 reconstruction filter to replace the suggested 3 x 3 filter, and the addition of a reconstruction threshold to preserve image edges. This method is compared experimentally to the original algorithm and also to JPEG compression in terms of complexity and resulting image quality.

Image compression via improved quadtree decomposition algorithms

Quadtree decomposition is a simple technique used to obtain an image representation at different resolution levels. This representation can be useful for a variety of image processing and image compression algorithms. This paper presents a simple way to get better compression performances (in MSE sense) via quadtree decomposition, by using near to optimal choice of the threshold for quadtree decomposition; and bit allocation procedure based on the equations derived from rate-distortion theory. The rate-distortion performance of the improved algorithm is calculated for some Gaussian field, and it is examined vie simulation over benchmark gray-level images. In both these cases, significant improvement in the compression performances is shown.