Progressive image transmission: an adaptive quadtree-pruning approach

Abstract

Summary form only given. Progressive, adaptive and hierarchical modes are desirable image coding features. This paper presents a quadtree-pruning pyramid coding scheme satisfying all these objectives. Pyramid coding is an approach suitable for progressive image transmission, where the original image is divided into different levels that correspond to successive approximants of the original one. Starting from the original image, a sequence of reduced-size images is formed by averaging intensity values over 2/spl times/2-pixel blocks. This sequence, called the mean pyramid, ends with an image with only one pixel. Then another sequence of images, called the difference pyramid which can be further encoded via vector quantization, is formed by taking the difference of two consecutive images in the mean pyramid. Our quadtree-pruning approach uses only the mean pyramid. Experiments show that the quadtree-pruning pyramid method is quite efficient for lossy compression. Our approach can also be used for lossless compression by simply setting the threshold function to be zero.