Image Denoising Based On Nonlinear Diffusion And TV Method

Image is an important source of information. Due to noise mixed with process of information acquisition, transmission, storage and so forth, which degrades the quality of image. Image denoising becomes an important task of digital image processing. A comprehensive research on edge preservation, channel coupling, adaptive gradient function of image denoising using nonlinear diffusion and total variation method are made in this dissertation, which mainly includes the following contents:At first, the recent developments and application fields of nonlinear diffusion and total variation method were introduced; some improved models which based on P-M and ROF model are listed too. The principles of these methods are analyzed. Based on these analyses, the main work can be listed as follow:Both TV flow and edge enhancing flow are analyzed; a basic coupled method for color image is mentioned. In order to remove noise effectively and preserve edges and key details in color image, considering the information of each channel of color image and the advantages of denoising and edges preservation of TV flow, a channel couple-d diffusion model which based on TV flow is proposed, the function of the forward and backward diffusion are also included.The staircase which is the main side effects of ROF model is analyzed, and the characteristics of Bing Song adaptive method are also studied and its property of edge diffusion with respect to different region of parameter p are proved. Besides, Bomgren adaptive gradient function method is also introduced, some of its characteristics of edge preservation and denoising effect are listed. Due to the defect of the adaptive gradient function which limited the method's denoising and edge preservation abilities, an improved adaptive gradient function is proposed, new function allow researcher choosing parameter beta according to the magnitude of objects in the images to rescale the transition region, through this method, the model can prevent some low-intensity edges being smoothed.At last, the methods for image denoising proposed in this paper are tested respectively. Experimental results show that the channel coupled TV diffusion model is better preserving geometric information such as edges in addition to its effectiveness for image denoising. Besides, the properties of forward and backward diffusion based on the new model are not changed in color image denoising; At the mean time, the results show that Bomgren model which adopted improved adaptive gradient function not only prevent the staircase, but well capture edge and remove noise with different intensity of images.