Quadtree Segmented Wavelet Transform Image Coding

Abstract

Wavelet transform has been received a great interest because it provides a multi-resolution representation of images. Wavelet transforms have been shown to achieve high compression ratios while maintaining very good image quality, due to the fact that edge characteristics of images can be well preserved by this method at low bit ratesBy way of vector quantization technique, the wavelet transformed coefficients can be further compressed. For real time image compression, achieving high data compression ratio and coding efficiency at the same time are both important. In this study, we have proposed a preprocessed quadtree segmentation method for Wavelet transform image coding. Quadtree segmentation algorithm is used to divide a given image, where regions with image detail will be segmented into blocks with smaller block size, and the background of the image will be assigned larger block size. Each image sub-block is coded by Wavelet transform scheme to gain a better compression quality. After the wavelet transform, to select appropriate size for codebook, bit allocation assignment is applied associated with the variance of each subband image block. We have also adopted rate-distortion concept to adjust the compressed bit rate. For this proposed compression scheme, simulation results show that we can achieve acceptable visual quality and high compression ratio simultaneously. Furthermore, due to the small size of the codebook, we are able to reduce the computational time. System performance analysis is demonstrated in this study.