Abstract: This paper mainly presents some improvements on computing discrete cosine transforms (DCT) and quantization part in the standard of JPEG image processing.Among these,the method of searching tables takes place of general DCT method for rasing the computation speed.In quantization part,the author use a vector quantization scheme based on simple and efficient “double test algorithm” instead of the general Euclidean distance vector searching algorithm,apparently speeding up the codebook searching speed.

Key words: image compression, alternative coding, run length encoding；DCT, JPEG