EFFICIENCY OF SHAPE-ADAPTIVE 2-D TRANSFORMS FOR CODING OF ARBITRARILY-SHAPED IMAGE SEGMENTS

In this letter we introduce a formula to compute an optimum 2-D shape- adaptive Karhunen-Loeve transform (KLT) suitable for coding pels in ar bitrarily-shaped image segments, The efficiency of the KLT on a 2-D AR (1) process is used to benchmark two other shape-adaptive transforms d escribed in literature, It is shown that the optimum KLT significantly outperforms the well known shape-adaptive DCT method introduced by Gi lge et al. for coding segments of arbitrary shape in intraframe coding mode, A statistical transform gain close to the Gilge-method can be a chieved with a shape-adaptive DCT algorithm introduced by Sikora and M akai which is implemented with much lower complexity.