说明：  openCV特征提取代码总结，包括：颜色直方图提取，形状特征提取，角点提取、Hough直线提取、边缘提取、纹理特征提取等等。
(OpenCV feature extraction code summary, including: color histogram extraction, shape feature extraction, angular point extraction, Hough straight line extraction, edge detection and texture feature extraction and so on. )