图像变换 将图象分块(8*8)，作DCT变换，并作IDCT：DCT是一种可分离图象变换，用来图象压缩编码，IDCT用来解压缩-Image transform to image sub-block (8* 8), for the DCT transform, and IDCT: DCT is a separable transform image to image compression coding, IDCT used to extract