说明：  Canny算子是边缘检测的一种最优算子,能检测出单像素、连续的边缘。这些特性对后续处理很有帮助。 本算法包含了一般的canny算子，还包括使用大津值自适应高、低阈值的canny算子。
(Canny edge detection operator is one of the best operator, can detect a single pixel, the edge of a row. The follow-up to deal with these features helpful. The algorithm contains the general canny operator, but also including the use of adaptive Otsu high value, low-threshold canny operator.)