如果从区域中的一个像素出发，经连续地向上，下，左，右四个相邻像素的移动，就可以到达区域内的另一个任意像素，就称区域是四连通的。从而实现四连通填充。-If a pixel region of the continuously up, down, left, right of the four adjacent pixels mobile, you can reach the region of another arbitrary pixel, is four connected region.