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| A Novel Nonlinear Method for Image Enhancement Based on Nonsubsampled Contourlet Transform |
| Zhang Lin①②; Zhu Zhao-da① |
| ①College of Information Science & Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; ②Radar and Avionics Institute of AVIC, Wuxi 214063, China |
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Abstract To overcome the limitation of traditional image denoising algorithms, a Novel Nonlinear Image Enhancement Method based on NonSubsampled Contourlet Tansform (NNIEM-NSCT) is proposed in this paper. The method not only preserves the details of image edge but also suppresses the noise by means of an adaptive Bayes shrinkage threshold which takes advantages of the relationship across all subbands in the same level. Secondly, a nonlinear enhancement mapping function is constructed by modifying the NSCT coefficients to change the image enhancement of weak and strong edges efficiently. Experimental results show that the proposed method outperforms the NSCT-based method. The Detail Variance (DV) of proposed method improves about two times more than that of NSCT-based method, when the Background Variance (BV) is almost equal, and a better visual effect is gotten.
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Received: 26 August 2008
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2009, Vol. 31 
