A Study On Digital Image Coding Of Fractal

The main shortcoming of the digital image is that it will need large numbers of bit to storage and transmitting. The image compression can solve the problem. It can reduce redundancy of the image data in order to be able to store or transmit data in an efficient form .There are a lot of methods of image compression ,Fractals is one of them.In this paper , fractals is the main aim of research..The characteristic of fractals image compression is that it can get high compression ratio in theory. Up to now, the automatic algorithum of fractal can't get the satisfied result. One of the shortcomings of the algorithum is that it can't get the high PSNR when the compression ratio is high.The other is that the speed of coding is slow. Many people are attracted by fractal algorithum. There is plenty of good advice has been given . The work of this paper is based on the automatic fractal algorithum and the advice .The main work and innovation1 In general , a image compression method has different effect to different image . Some are fit for image which has much high frequency . Some are fit for image which has much low frequency .This paper analysis the applicability of fractal algorithm . In this dissertation , an improved algorithum is given . The basic algorithum without eight change and the joint use of quantitative coding , The compression ratio and PSNR can be adjusted , and it can get more quickly speed of coding .2 To a group of exact fractal code , the decoding image can be any resolution .With this characteristic ,choose the proper domain block and range block,this paper get an algorithum which can get higher decoding PSNR and speed than the basic fractal algorithum.3 Give a new method to calculate the scale factor . The calculation of basic algorithum is complex and enormous . The factor of scale is an important variable of the basic algorithm. Now there are two methods to calculate the factor of scale .A new method was given to calculate the factor of scale. The calculation load and complexity are reduced by the new method. Compared with the basic algorithm , the method can reduce coding time.4 The basic fractal algorithum is based on the Collage theorem and contraction mapping theorem . A mathematic model based on basic fractal algorithum is given . Give the determinate expression of any pix in a simple image . Analyse essentiality of the offset factor . At last give a corollary that the value of a pix in a attractor which is get by basic fractal algorithum can be give by a determinate expression . The choose of contraction affine transform must be in accordance with certain rules .