Coding for binary images based on mathematical morphology is a hotspot of research in recently years. A new method presented here based on ultimate erosion

subset of skeleton

removes more redundancy using morphology analysis. Following a review of the theoretical background and old research work on this area

such as a method based ultimate erosion for coding binary images proposed by kresch etc . We proposed a new theorem to predicate non skeleton pixel after analyzing the old method . It was proposed a new condition to predicate non skeleton pixel in the new theorem. Compar ed with the old theorem

pixels...More pixels can be determined to be non skeleton when being encoded under the new theorem and the efficiency is increased. The corresponding corollary was also presented to realize the theorem in computation. The proposed method is suitable for progressive transmission and can be fast implemented by hardware. A binary image "tools" was tested by this method and a better result

0.065 bit/pixel

was gotten

compared with other methods

such as runlength

quadtree or chain coders. It is also better than the old method

0.071 bpp.