Improving compression time in zero-tree based image coding procedures

In this paper, a novel scheme for the accelerated analysis of quad-trees in the discrete wavelet spectrum of a digital image is proposed. During the pre-scanning step, the proposed scheme generates objective and specially structured binary codes for the whole set of quad-tree roots (wavelet coefficients) and thereby accumulates facts on the significance of respective descendants (wavelet coefficients comprising quad-trees on the view). The developed scheme can be successfully applied to any zero-tree based image coding procedure, such as the embedded zero-tree wavelet (EZW) algorithm of Shapiro and set partitioning in hierarchical trees (SPIHT) by Said and Pearlman. Exceptionally high performance of the proposed quad-tree analysis scheme, in the sense of image encoding times, is demonstrated using the EZW algorithm and the discrete Le Gall wavelet transform.