Jpg Image Compression Encoding And Decoding Of The Design And Realization

This thesis introduces the encoding and decoding of JPEG. The encoding part of this program can encode a picture whose format is BMP turn to JPEG. Then we can save the document into binary system. The decoding program can decode the compression data and reconstruct the origin image. On the process of transporting, we often use the form of JPEG to encode the frozen pictures. JPEG is one of the loss compression which can not recover all the image data, some data are losted. Although we look forward to non-lossy compression. However, the compression ratio of lossy compression is bigger than that non-lossy compression. The encode of JPEG translates image color from RBG to luminance Y and chroma Cr,Cb. Because our eyes are less sensitive to chroma comparing with luminance , some of chroma data are abandoned to reduce data size.The thesis introduces the compression scheme of JPEG firstly, including its history and the basic situation of this stage, compression principle, and so on. Referring to the JPEG compression method, the thesis focuses on the basic tenets of Huffmen coding and run-length coding and their specific application in JPEG compression algorithm. To transform coding method as an example, it introduces the discrete cosine transform (DCT) the basic process. Finally, Using the VC + +to compile the compression process involves several basic modules of JPEG. Realizing the transporting from BMP to JPEG is the most important ideological basis for programming.JPEG envolves some kinds of ways of encoding including Run Length Coding and Huffmen Coding, so it has high compression ratio. Before coding, we divide data into blocks, DCT and quantization. The low-frequency signals that have more energy are maintained and others are rejected . While decoding , data stream are readed , decoded , inverse-quantified and then IDCT .