The Research On Digital Image Hybrid Compression Coding Methods

Image compression encoding is one of the key techniques in modern multimedia and communication field. The methods of image coding are of a great variety currently, every kind of coding methods all exist respectively merit and shortcoming. For obtaining better code result, the hybrid image coding in which the different method combine has become to study in the last few years.This paper summarizes the current mainstream principle and method of hybrid image compression coding algorithm. In-depth analysis of the two types of hybrid image coding algorithm:the image coding algorithms based on DCT coefficients rearranged by wavelet structure and based on morphological representation. It stresses that that proper reorganization of DCT coefficients have similar characteristics to wavelet transform. The former takes advantage of DCT and zero-tree encoding ,which has high practical value. The image coding based on morphological representation directly to important coefficients of the wavelet sub-band can further reduce the computational complexity.The paper presents an improved method to the morphological representation of DCT coefficients for image compression. The improvement mainly includes:The different characteristics aimed at each sub-band of DCT reorganization coefficient to take, the lowest frequency sub-band is coded alone. The other sub-bands are coded by using the different structure element, so it can make the better use of coefficients distribution characteristics of the different sub-bands .The experimental results show that the algorithm is not only better than EZ-DCT , but for the Lena and Goldhill image this improved algorithm out-performs the basic MR-DCT respectively 0.15-0.30 and 0.18-0.40 dB in PSNR, and the algorithm is more effective for the complicated texture image.