对原始灰度图像 Lena_gray.bmp进行图像压缩实验 1．对此图进行 8×8 DCT 变换后，分别只保留 DC系数，以及保留前 4、8、16 个变换系数(DC＋AC) ，然后再分别进行 IDCT 变换，比较结果。 2．可以使用 Matlab - Image Processing Toolbox 中的函数实现。-gray image of the original image compression Lena_gray.bmp an experiment. This diagram 8 8 DCT, the only difference reservations DC coefficient, and the preservation of the former 4, 8 or 16 DCT coefficients (DC+ AC), and then separately IDCT transformation, the results of the comparison. 2. Using Matlab-Image Processing Toolbox to achieve the function.