说明：  JPEG压缩编码的主要步骤有： 1.通过前向离散余弦变换减少图像数据相关性； 2.利用人眼的视觉特性队DCT系数进行量化； 3.使用查分脉冲编码调制对直流系数进行编码； 4.对交流系数进行Z形扫描，使用形成长度编码队交流系数进行编码； 5.熵编码器对上述描述符进行熵编码。
(JPEG compression encoding of the main steps are: 1.forward discrete cosine transform to reduce the image data 2.Using human visual characteristics of the team DCT coefficients are quantized 3.check points pulse code modulation encoding the DC coefficient 4.coefficients of the Z-scan AC coefficient is encoded using the form length encoding team 5.the entropy encoder for entropy coding of the above descriptors.)