地图代数概论的一个作业。实现栅格距离计算功能，输入为白底的bmp位图，有颜色的部分被认为是空间实体进行处理，得到按距离染色的bmp位图-An Introduction to Map Algebra of a job. Grid computing to achieve the distance function, input of the bmp bitmap white, colored part of the spatial entity is considered to be proces