Fractal based Image Compression techniques - A progress Report

One well-known loss-less image technique is DCT-based JPEG compression that is quite effective at low or moderate compression ratios, up to ratios of 20 or 25 to 1. Beyond this point, the image becomes very “blocky” as the compression increases and the image quality becomes too poor for practical use. Another drawback of JPEG compression is its resolution dependence. In order to “zoom-in” on a portion of an image and to enlarge it, it is necessary to replicate pixels. The enlarged image will exhibit a certain level of “blockiness” which soon becomes unacceptable as the expansion factor increases. Because of this problem, it is sometimes necessary to store the same image at different resolutions, thus wasting storage space. So, although JPEG is now a well-established standard for lossy image compression, it has its limits and alternative compression methods must be considered. Wavelet-based methods are gaining popularity. They are similar in spirit to the DCT methods but do not suffer from some of its shortcomings. Another technique that is become very popular is fractal image compression. It really shines for high compression ratios, or when zooming on a portion of an image or enlarging a complete image. Some fractal based lossy image compression techniques i.e. FICAQP, FCI-HV and FLCD-HV are proposed by the candidate. FICAQP offers better compression rates most of the times with comparatively improved PSNR. But, the compression time of the fractal image compression with proposed partitioning scheme is much more than quadtree scheme. FCI-HV and FLCD-HV are better than quadtree partitioning in terms of compression ratio and faster than HV partitioning scheme. Keyword Fractal compression, compression ratio, Quardtree partition, Affine map, Iterated Function Systems (IFS),Partitioned Iterated Function Systems (PIFS), Region Based Huffman (RBH), Compression, Modified Region Based Huffman (MRBH), Region Selection Algorithm (RSA), Huffman Tree, Frequency Table (FT), Symbol Code Table (SCT), LZW, dictionary-based compression, OLZW;