The Image Coding Based On Wavelet Transform

Image is important for us to obtain information. But it is difficult to save and transmit because of abundant data. Traditional image compression method mostly considers information theory instead of visual character. So it does not meet the requirement of people on compression ratio and subjective quality of reconstructive image. In this paper, we mainly study how to realize wavelet coefficient layered coding and transmission by exploiting the correlation of transformed coefficients. Thus, we can realize progressive transmission of image data.Firstly, we discuss the essentiality and feasibility of image compression, and detailedly introduce the development of image compression, the method of image compression, the metewand of image compression performance and the international standard of image compression.Secondly, we fully discuss and analyse the theory of wavelet transform, and study the approach of image coding through wavelet transform.Finally, EZW, SPIHT and SPECK algorithms based on wavelet transform are discussed and analysed in detail. SPIHT and SPECK algorithms are modified in order to be easy to be realized by hardware. The experimental results show that the enhanced algorithms are very effective. Region of interest(ROI) coding is one of the innovative functionalities supported by JPEG2000, ROI coding is incorporated functionality into SPIHT coding. By placing a higher emphasis on the transform coefficients pertaining to ROI, ROI is coded with higher fidelity than the rest of the image in earlier stages of progressive reconstruction, thus the "import" part of the image is reconstructed more quickly than the rest of the image.