Research Of Fast Fractal Coding Method Based On Adaptive Threshold

With the development of Network technology quickly, the multimedia technology based on image enriches our lives. However if there is no highly effective compression approach, image communication can not be achieved. The purpose of image compression coding is to represent images with few bits, maintain the quality of recovering images according with the requirements of certain application situations. Image compression is the key and bottleneck of multimedia technology.Up to now, some mature technologies have been developed in the area of image compression, such as DCT (Discrete Cosine Transform) and Huffman Code. Moreover, a series of international standards, such as JPEG, JPEG-2000, H.261, H.263, MPEG-1, MPEG-2, MPEG-4 and MPEG-7, have been formed on the base of these coding algorithms.Recently, many new coding methods have been proposed, such as Subband Coding, Wavelet Transform Coding and Fractal Image Coding, etc. Fractal Image Coding gets our great attention because it breaks the limit of previous coding and obtains the maximum compression ratio comparing with other algorithms.The paper has considered characteristics of the input image, given the calculating process of the adaptive threshold, and proposed a fractal image coding algorithm of threshold being in the direct ratio to the child block variance based on Fisher fixed threshold. The number of candidate block could be reduced because of the variance. Experimental results indicate that the coding time is shortened, the performance of PSNR of recovered image is improved, and the efficiency is increased. Due to the searching window of this method being fixed, the coding time has relative determinism, which benefit the hardware implementation of the encoder.Combination of the fractal image and wavelet is popular in recent years, so the paper proposes the tentative ideas on the combination of fractal image and wavelet coding at last.