Image enhancement based on multiple parametric sigmoid functions

In a digital still camera system, a dynamic range is usually compressed linearly in logarithmic space. Therefore, the images taken by the digital still camera tend to be low contrast, and give us a flat impression without the liveliness in comparison with the conventional silver halide photographs. In this paper, we propose a new digital image enhancement method by using multiple parametric sigmoid functions. In the proposed method, intensity conversions by using parametric sigmoid functions are carried out based on the information of local regions with various sizes. And, by synthesizing each conversion result, the fine image enhancement is achieved. The effectiveness of the proposed method is verified by applying it to some images.