Shape Adaptive All Phase Biorthogonal Transform and Its Application in Image Coding

In this paper shape adaptive all phase biorthogonal transform (SA-APBT) for coding arbitrarily shaped image segments is proposed. The proposed transform can be used in region-based image compression instead of the shape adaptive discrete cosine transform (SA-DCT). Region-based image coding method is made up of three procedures: image segmentation, contour coding and texture coding. An image is divided into region-of-interest (ROI) and background area by image segmentation. Both areas are encoded and decoded independently. Experimental results on test images show that compared with SA-DCT at the same bit rates, the PSNRs and visual effects of reconstructed images based on SA-APBT are comparable to the one based on SA-DCT especially at low bit rates. And the SA-APBT transform coefficients are quantized uniformly, while the SA-DCT transform coefficients are quantized according to different quantization steps in the quantization table. So the quantization based on SA-APBT is simpler and computational complexity is reduced.