利用改进的Sobel算子检测图像边缘,从水平、垂直、左右对角线的方向计算Sobel梯度，并且加入拐角的梯度值。-The improved Sobel edge detection operator, horizontal, vertical, left and right diagonal direction Sobel gradient calculation, and adding the value of the gradient of the corner.

基于MATLAB分辨出图像内部拐角特征，并加以绘图标注(Identify the inner corner features of the image and mark them)