A Study On Hybrid Fractal-Wavelet Image Coder

With the development of many new theories and new methods, a great deal of new image compression methods have been proposed in recent years. One of the most significant advances is the wavelet-based compression scheme that has been put into practice in the areas of compression of static images and motive images as well as a key part in some international standards such as JPEG2000. However, it is still a research hotspot that how to deal with the coefficients transformed from a digital image with wavelet in a more efficient way. The method of fractal image coding is proposed in recent years, and is a new technique used in the image compression. It is a new idea for image compression based on Fractal theory and Iterated Function System. Because of its new idea and high compression rate, fractal coding is abroad focused. It is one of the most futures in image compression at present.This paper discusses it in such conditions.First of all, this paper discussed the method of image compression encoding. Then the paper discussed the definition and characteristics of wavelet image coder and fractal image coder. The paper implemented SPIHT and Jacquin fractal algorithms.This paper is based on the analysis of wavelet and fractal image compression, to find the way of mergence of these two methods, forming hybrid fractal-wavelet image coder, that is fractal encoding is applied only to the approximation subband, and a modified SPIHT coding is applied to the 3k detail subbands of wavelet transformed image, the detail information, encoded by modified SPIHT, is sent to the decoder, improving the reconstructed image quality. In the end of this paper, the proposed method has been compared to the pure fractal technique (Jacquin) and to the pure SPIHT wavelet coding. A significant improvement of subjective quality was achieved, avoiding blurring and causing no blocking effects at several bitrates and images, which confirms the PSNR objective measures obtained.