Research On Embedded Image Coding Algorithm Based On Wavelet Transfor

As people use images more and more frequently,the cost of image transmission and storage increases gradually.In order to reduce the pressure of image storage and transmission,we need to compress images.Wavelet transform can concentrate most of the information of the image,which is very suitable for the needs of image compression.Therefore,this paper focuses on two image coding algorithms based on wavelet transform,namely Embedded Zerotree Wavelet(EZW)algorithm and Set Partitioning In Hierarchical Trees(SPIHT)algorithm.In view of the shortcomings of these two algorithms,we improve these two algorithms.Firstly,This paper proposes an improved EZW algorithm.According to statistics,there are a large number of invalid subbands in the early stage of coding.The improved EZW algorithm adds subband coding,thereby omitting the coding of the coefficients in the invalid subbands.And make improvements to the coefficient encoding,by increasing the types of characters,removing redundant characters and using a compressor to reduce the number of encoded characters and improve the compression performance.In order to prevent making errors during decoding,the encoding of the primary process and the secondary process is separated by a character.Secondly,an improved SPIHT algorithm is proposed.Due to the correlation between the lowest frequency sub-band coefficients,the lowest frequency sub-band coefficients are encoded by DPCM for lossless predictive coding,which reduces the loss of information and the amount of computation.And in the high-frequency subband coefficient coding process,the compression performance is improved and the coding time is reduced by changing the initial threshold calculation method,reducing the code of importance of direct sub-nodes and removing unnecessary scanningIn this paper,multiple images are used for experiments,and the peak signal-tonoise ratio(PSNR)and structural similarity(SSIM)are used to evaluate the quality of the reconstructed images.The experimental results show that the compression performance of the two improved algorithms is better than the original algorithm,and the encoding time of the improved SPIHT algorithm becomes shorter,but the encoding time of the improved EZW algorithm becomes slightly longer.