A new encryption algorithm was proposed to apply to both square and rectangular image encryptions.A new two-dimensional map based on image segmentation was applied to the location scrambling,and a spread function containing chaos map to the gray scrambling,so that an image encryption algorithm combined with both position and gray scramblings was obtained.The experimental simulation shows that this algorithm can achieve good image encryption for any size of square and rectangular images with a large key space(10¹⁵～10³⁰).Proposed algorithm also has advantages in withstanding statistical and known plaintext attack,which basically satisfies the requirements of validity and safety for image encryption.