frequencycoefficients

代码说明：

  将图像分为nxn的分块,之后将各分块三个颜色通道的直方图平均化,最后进行离散余弦变化,分别提取各通道低频系数(The image into nxn sub-block after block of all three color channels of the histogram equalization, and finally the discrete cosine change, were extracted from the low frequency coefficients of each channel)