The edge of image is manifested as discontinuity in image, what edge detection means is to doled (in the image ) those discontinuous points or sharp variation points.
图像的边缘表现为图像上的不连续性，边缘检测就是检测图像上的不连续点或陡变点。
2
Based on the variation principle, the composite element method (CEM) is studied for seepage analysis considering discontinuous surfaces and drainage holes.