Abstract: According to the different diffusion demand of image in tangential and normal direction, the different diffusion parameter is set. In the tangential direction, the diffusion should be large enough to remove noise efficiently, so the diffusion parameter is 1. In the normal direction, the diffusion demand is different in the interior and edge of an image. We control the threshold of gradient modulus by the morphology method. After substituting the stable threshold by this adaptive threshold in Perona-Malik diffusion parameter, the suitable normal diffusion parameter for the instant image is obtained. The intention is that the interior and edge can be distinguished effectively and the edge information can be preserved as much as possible. Experimental results show that our method has an obvious effect in preserving small details.

Key words: morphological, practical differential equation, gradient modulus, image denoise