说明：  Canny 算子 是一个具有滤波、增强和检测的多阶段的优化算子。在进行处理前，Canny 算子先利用高斯平滑滤波器来平滑图像以除去噪声( 即用高斯平滑滤波器与图像作卷积) 。
(Canny operator is a filtering, enhancement and optimization of multi-stage detection operator. Before treatment, Canny operator first use Gaussian smoothing filter to smooth the image to remove noise (ie with a Gaussian smoothing filter with the image as a convolution.))