基于边缘图像分割算法，GAC，当图像中的对象和背景的边界处灰度值存在较大差异，那么对象的边缘就形成明显的轮廓-Based on the edge image segmentation algorithm, GAC, when the image of the object and the background of the edge of the gray value there is a big difference, then the edge of the object to form a clear contour