HOG特征通过计算和统计图像局部区域的梯度方向直方图来构成特征，程序可以对图片中的hog特征进行可视化梯度大小和方向。(The HOG feature is constructed by calculating and counting the gradient direction histogram of the local area of the image. The program can visualize the gradient size and direction of the hog feature in the image.)