Shape-adaptive DCT and Its Application in Region-based Image Coding

To get better and flexible performance, region-based image coding has been studied widely in the last few years. In region-based image coding, the whole image can be divided into two parts: region-of-interest (ROI) and background area. ROI is coded in low compression ratio, while background area is coded in high compression ratio. In this paper, shape-adaptive DCT (SA-DCT) for coding arbitrarily shaped image segments is introduced. And two region-based image coding methods using discrete cosine transform (DCT) and SADCT are presented. The algorithm based on SA-DCT is comparable with the one based on DCT in terms of reconstructed images’ effects. Experimental results show that the algorithm based on SA-DCT performs better than the one based on DCT both in subjective effect and objective effect. Therefore, SA-DCT is a more suitable transform for region-based image coding than DCT.