A low bit-rate hybrid DWT-SVD image-coding system (HDWTSVD) for monochromatic images

In this paper, we propose a new low bitrate algorithm to encode monochromatic images that combines DWT and SVD techniques. At the encoder side, the input image is divided into blocks (tiles) of 64×64 pixels. A criterion based on the average standard deviation of 8×8 subblocks is used to choose DWT or SVD. If the tile exhibits a high average standard deviation, it is compressed by using SVD otherwise by DWT. Eigenvalues and eigenvectors are scalar and vector quantized respectively. The Daubechies 9/7 filter bank factored into lifting steps is used for the DWT. The maximum number of levels of subband decomposition for each tile is 3. Each subband is coded using the homogeneous connected-region interested ordered transmission (HC-RIOT). At the decoder side, the header of each compressed tile is read and the information is sent to the HC-RIOT decoder or to the inverse quantization, in order to recover the tile. This new algorithm is applied to image coding and its performance is discussed.