DCT变换的特点是变换后图像大部分能量集中在左上角，因为左上放映原图像低频部分数据，右下反映原图像高频部分数据。而图像的能量通常集中在低频部分。-The characteristics of the DCT transform is transform image on most of the energy in the top left corner, because the upper left original image data show the low frequency part, lower right reflect the original image high frequency part of data. And the image of energy in the low frequency part is usually focus on.