Inverse pyramidal decomposition with multiple DCT

Abstract This paper presents a method for pyramidal image decomposition called “inverse” because of the order followed to obtain the pyramid levels: from top to bottom, in correspondence with the requirement for “progressive” image transmission. The pyramid top (level zero) consists in selecting the low-frequency coefficients of the discrete cosine image transform. The following pyramid levels are made up of low-frequency discrete cosine transform (DCT) coefficients of the subimages obtained from quadtree division at each level. The quadtree root coincides with the pyramid top. The first level is the difference between the image and its approximation obtained by inverse DCT. The following (second) level is a difference too, between the previous (first) level and its approximation obtained with inverse DCT for every subimage in the first level, etc. The paper describes the principle of image decomposition, the possibilities for recursive calculation, its basic characteristics and modifications. The block diagram and the generalised scheme of the decomposition are given and some results of its modelling show the application capacities in image coding systems.