边缘一般对应着灰度有突变的地方，即高频成分。灰度的突变可以通过求导进行检测。常见灰度突变有：阶梯状、脉冲状、屋顶状-Generally corresponds to the edge of gray areas have mutations, that is, high frequency components. Gray-scale mutations can be detected through the derivation. Common gray-scale mutations inc