A novel coefficient scanning scheme for directional spatial prediction-based image compression
Spatial prediction is a promising technique for image coding. For example, the coming AVC/H.264 standard adopts directional spatial prediction in the intra frame coding. Similar to the traditional DCT-based image coding schemes, it still scan the transform coefficients in a zigzag order, which is inefficient for coding the residual signals predicted from the different directions. To tackle this problem, a new scheme of scanning the transform coefficients by utilizing the spatial prediction information is proposed in this paper. The distribution of transform coefficients from each direction of spatial predictions is fully studied. According to the statistics, the adaptive scan table is derived for each type of spatial predictions, which is indicated by the prediction mode. Experimental results demonstrate that the proposed scheme can always outperform the JVT codec using zigzag scanning. Moreover, it does not introduce any extra computing costs in software implementation.