Less-visible contrast enhancement based on the human visual perception

Typically, conventional image-enhancement methods have a common problem concerning the over-enhancement in an image which contains both less-visible and nicely-visible areas. To solve such problem, we propose a new contrast enhancement method based on the singular value decomposition (SVD), an adaptive non-linear scaling function, and a pyramid-based blending method. The SVD is used to decompose an image and to identify image noise if the image contains high noise level. Then, the less-visible areas of the noise-removal image is strengthened by using the proposed adaptive non-linear scaling function based on the human perception. Finally, the proposed pyramid-based blending scheme is deployed in order to recover nicely-visible area of the image. This recovery process is mandatory because enhancing images in the previous step might cause the over-enhancement. Objective and subjective evaluations were conducted, and experimental results show that our proposed method can successfully improve the less-visible contrast without amplifying noise. It also preserves the tone and texture of original images and produces satisfying results in terms of human preference.