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 constituted by the pixel dots of different gray level and an adjacent domain points. Thus, if you want to enhance edges, it should be highlighted the gray level changes between adjacent points. The differential operator is used to find the rate of change of the signal, which has the role of strengthening the high-frequency component. If its application in the image on the outline of the image can be clear. Often not possible to determine the orientation of the contour, and thus the selection differential operator midnight, you must select those who do not have the space directional rotation invariant linear differential operator for edge enhancement.