Abstract: Benefited from the topology of polygon mesh, the traditional scan line algorithm dealing with a single polygon is extended to deal with a polygon mesh. It enables multiple polygons to be scanned simultaneously, thus reduces the costs on repeatedly finding intersections and scan line conversion during the whole process. The paper presents a general algorithm for mesh based image processing, and compares its efficiency with the traditional approach. An application of the algorithm in high precision image rectification is introduced and its efficiency discussed.