拐点的检测，对一个图像的拐点进行检测，使用的是freeman链码的方法，检测图像中拐点的方向，确定该方向是不是拐点。-Inflection point detection, an image of the inflection point for testing, use freeman chain code method, testing the image in the direction of the inflection point, we determine the direction is inflection point.