先将图像分为4*4的重叠分块,然后将各个分块的三个颜色通道的直方图平均化,再将其进行离散余弦变化,分别提取各个通道的低频系数.,First image is divided into 4* 4 sub-block overlap, and then each sub-block of the three color channel histogram equalization, and then its discrete cosine Change, were extracted from each channel of the low-frequency coefficients.