说明：  用于图像边缘的羽化操作。主要有两种羽化操作，与另一个源码（均为matlab）向背景羽化操作不同的是，这是向白色进行过渡，即在图像边缘进行由图像到白色过渡的处理。
(Feathering operation for image edge. The main the two feathering operating feathering operation and another source (both matlab) to the background is different, this is to white transition, i.e. the edge of the image processing by the image to white transition.)