Research On Fractal Image Compression Algorithm Based On Lifting Wavelet Transform

With the rapid development of information networking in recent years,the multimedia technologies applications plays a very important role in people's life.The transmission and storage of the digital image plays an important part in it.Owing to digital image's data is very large,so it cannot satisfy the request of the practical application before effective compression.On this occasion,it inevitably becomes one of the most important directions in the field of communication and signal processing to seek after the effective image coding algorithm.Fractal image compression(FIC) takes advantage of self-sinilarities which exist in the images commonly.It uses the self-similarity in different scales of image to find the corresponding fractal description and remove the geometry redundance.FIC is one of the most competitive schemes in recent research,and it has the capable of achieving good image quality at a very high compression ratio.The main drawbacks of FIC are the expensive computational cost in the encoding process,the convergence in decoding process,the block-effect in decoding image,etc.In this thesis,we combine FIC and lifting wavelet transform,we can get much higher compression rate and short encoding time.The major jobs are described as follows:(1) An improved fractal image compression algorithm based on annular neighbour-searching is proposed.Compared with the traditional FIC algorithm,the algorithm can find the best domain block that conforms to assigned error in the shortest time,and decrease the encding time significantly.(2) The importance of each subimage after wavelet decomposition is inequablity in human visual system,the lower frequency has higher importance,and the higher frequency has lower importance.Based on this,combined with the visibility preaccentuation before the quantization,an image compression algorithm based on lifting wavelet transform is designed.This algorithm decreases the edcoding time,and improves the quality of decoding-image.(3) A fast fractal image compression algorithm based on the lifting wavelet transform is proposed.It combined the good points from wavelet encoding and fractal encoding.The algorithm uses the lifting scheme of Daubechies9/7,and codes the coefficient by SPIHT or improved-fractal encoding for the different images.The experimental results show that the proposed method can reduce the encoding time,avoid the blocking effects,and get a better decoding image.Finally,the research work involved in the thesis is summarized,and the future developments in fractal image compression are forecast.