在图象中，边缘是由灰度级和相邻域点不同的象素点构成的。因而，若想增强边缘，就应该突出相邻点间的灰度级的变化。微分运算可用来求信号的变化率，因而具有加强高频分量的作用。如果将其应用在图象上，可使图象的轮廓清晰。由于我们常常无法事先确定轮廓的取向，因而挑选用于轮廓增强的微分算子时，必须选择那些不具备空间方向性的和具有旋转不变的线形微分算子。-In the image, the edge is adjacent to the gray-scale and different domains consisting of the pixel points. Thus, if the edge enhancement, it should highlight the points between adjacent gray-scale changes. Differential operator can be used to signal changes in the rate of demand and thus to strengthen the role of high-frequency component. If the images on their application, will enable a clear outline of the image. Since we often can not be pre-determined orientation of the outline, so the selection for the differential operator to enhance the outline of midnight, to choose those who do not have the space and the direction of rotation-invariant linear differential operator.