实现jpeg压缩和解压缩,将彩色图像进行颜色空间转换、对不同的颜色分量进行不同的采样、对于3个分量进行8×8的DCT变换、对DCT系数矩阵按照JPEG推荐的量化表进行量化；对量化后的系数进行Z形扫描，最后进行熵编码，形成码流，计算比特数，和压缩比。解压从量化后的DCT系数表开始逆向进行-Jpeg compression and decompression, the color image is a color space conversion, the different color compo

对512x512的lenagray.jpg图像分别采样为256x256、128x128、64x64的图像； 对lenagray.jpg图像分别量化为64级灰度图像、32级灰度图像、8级灰度图像和4级灰度图像。(The lenagray. jpg images of 512x512 were sampled as 256x256, 128x128 and 64x64 images respectively. The lenagray.jpg image is quantized into 64-l