对一副二维数字图像执行多尺度全方位的膨胀处理，以提取出图像的外边缘。算法简单，易于实现，且边缘提取的效果优于传统的基于灰度梯度的边缘提取算子。-A pair of two-dimensional digital image on the implementation of multi-scale expansion of a full range of treatment to extract the outer edge of the image. Algorithm is simple, easy to achieve, and edge detection is better than the traditional gray-scale gradient based edge detection operator.