Image filtering and enhancement play a very important role in digital image processing.The anisotropic diffusion is a selective smoothing technique that effectively employs intra-region smoothing without limitation and inhibits inter-region smoothing.In order to remove noise effectively and preserve edges and key details

a more effective and adaptive diffusion algorithm is to be proposed in this paper.We build a new diffusion coefficient in partial derivative equation(PDE) with the advantages of two existing diffusion coefficients and incorporate the proposed scheme with the nonlinear time-dependent cooling technique for gradient threshold.The proposed algorithm is based upon a selective and improved diffusion coefficient and performs adaptively towards different gradients.The improved algorithm not only preserves image edges

but also smoothes small scale features and avoids distortion of image edges and details. It has been shown from the experiments that the improved scheme has superiority capability over the Perona-Malik scheme and it is a robust anisotropic diffusion.