Optimization Of JPEG2000 CODEC

With the rapid development of multimedia technology, it makes the digital image more available in the daily life. Considering large picture and limited bandwidth of the Internet, that makes the digital compress technology as the core part of the image technology. JPEG is the first international standard as to compression of still image. JPEG baseline system is based on 8×8 block DCT(Discret Cosine Transform),ZigZag scanning,entropy coding and so on. JPEG2000 is a new generation still image compression standard established by ISO(International Standard Organization). Compared to JPEG, JPEG2000 introduces DWT(Discret Wavelet Transform) to replace DCT, do uniform quantization to all the sub-bands, and transformation coefficients are encoded by Half-adaptation arithmetic encoding with context. Due to all kinds of above core technology, JPEG2000 performs better than JPEG in compression. In addition, JPEG2000 has other advantages: Progressive Transmission,ROI(Region of Interest) coding, direct accessness and processing of bit stream, error tolerant mechanism,open framed structure and so forth. Those technology make JPEG2000 become the hot point of research in image coding later.This paper introduces some key technology of JPEG and JPEG2000,and do detailed research on CODEC system of JPEG2000.Based on detailed research on the open source OpenJPEG,this paper uses Profile in Visual C++6.0 to get the running time of each module and do optimization and improvement to those modules with high algorithmic complexity. Several optimation methods are adopted,for example, Intel MMX/SSE is used to optimize and dynamic data strcuture for improving efficency. In this paper, the comparison between before and after optimation is provided. Finally,a basic JPEG2000 codec sytem is realized by Delphi 7 and Visual C++ 6.0.Cmpared to JPEG, a conclusion can be drawn:JPEG2000 is better than JPEG in PSNR at diffierent bit rate during the compression of standard image and get a good performance compared to other commercial software.