中文说明：能够提取出图像I的HOG特征，返回其幅值，角度和在各个角度上的幅值。是进行其他针对图像的HOG特征提取的前一步。
English Description：
The hog feature of image I can be extracted, and its amplitude, angle and amplitude in each angle can be returned. It is the first step for other hog feature extraction.