描述了如何提取方向图。输入图像必须是归一化的图像，这样才能有较好的效果。输出图像覆盖于输入图像之上。代码由C写成。详细情况见解包后的说明-describes how to extract pattern. Images must be imported under one of the images, in order to have better results. Image output coverage to the importation of images above. Written