边缘检测算子
图像边缘信息主要集中在高频段，通常说图像锐化或检测边缘，实质就是高频滤波。我们知道微分运算是求信号的变化率，具有加强高频分量的作用。在空域运算中来说，对图像的锐化就是计算微分。由于数字图像的离散信号，微分运算就变成计算差分或梯度。图像处理中有多种边缘检测（梯度）算子，常用的包括普通一阶差分，Robert算子（交叉差分），Sobel算子等等，是基于寻找梯度强度。拉普拉斯算子（二阶差分）是基于过零点检测。通过计算梯度，设置阀值，得到边缘图像。(The image edge information is mainly concentrated in the high frequency section, usually the image sharpening or detecting the edge, the essence is the high frequency filtering. We know that differential operation is the change rate of the signal, and it has the function of strengthening the high frequency component. In the space operation, the sharpening of the image is the calculation of differential. Because of the discrete signal of the digital image, the differential operation becomes the difference or the gradient. There are many edge detection (gradient) operators in image processing, which usually include ordinary first order difference, Robert operator (cross difference), Sobel operator and so on, which are based on finding gradient intensity. The Laplasse operator (two order difference) is based on the zero crossing point detection. By calculating the gradient, the threshold is set to get the edge image.)