zahra mortezaie - Faculty of Computer Engineering,Faculty of Computer Engineering, Shahrood University of Technology, Shahrood, Iran Shahrood University of Technology, Shahrood, Iran.
Hamid Hassanpour - Faculty of Computer Engineering, Shahrood University of Technology, Shahrood, Iran
Sekine Asadi Amiri - Department of Engineering and technology, University of Mazandaran, Babolsar, Iran

Un-sharp masking method improves the images contrast without requiring any prior knowledge. In this method, a sharper image can be achieved by empowering the high frequency components of the input image. Un-sharp masking has a parameter named gain factor which has a high effect on the enhanced image quality. In this paper, an approach is proposed to adaptively estimate the appropriate value of this parameter in order to effectively enhance an image with local blur, or an image with non-uniform blur. In proposed method, first, the input image is segmented into blur and non-blur regions. Then the gain factor is estimated for each region adaptively. In this approach, the influence of the image blurriness on its gradient information is used to estimate the value for the gain factor. The image quality assessments are applied to evaluate the performance of proposed un-sharp masking method in image enhancement. Experimental results demonstrate that the performance of our proposed method is better than the performance of existing un-sharp masking methods in image enhancement.

Un-Sharp Masking, Contrast Enhancement, Gradient Information, Non-Uniform Blur