The normal method of image edge detection does not connect each element of edge with the whole edges, therefore, there is neither losing the element nor retaking it, which make the edge rough.

• 摘要常用的边界提取方法均没有将单个边界元素与整个边界相联系，结果不是丢失边界元素就是增加边界元素，使图像的边界变得不甚平滑。