Variable block-size transform image coder

A discrete cosine transform image-coding scheme based on adaptive block size is proposed and demonstrated. The scheme adaptively optimizes the block sizes according to some local activity indices of the image scenes. The optimization algorithm is achieved by applying a technique from graph theory. Nine rectangular block sizes are used, corresponding to all combinations of 8, 16, and 32, pixels per side. The approach reduces interblock correlation between coefficients and increases the energy compaction in the transform domain. Experimental results are presented and compared to results obtained by an identical coder using a fixed block size