Author : Vidhya R and Sifna N Shajahan

This paper proposed an efficient algorithm for image enhancement. The contrast of image is very important characteristics by which the quality of image can be judged as good or poor quality. HE-based algorithms concentrated on the contrast of an image. Most of the existing image enhancement techniques focus on improving the global contrast of an image and have paid little attention to the local information such as the local contrast and edges. This issue is considered to be the inherent limitation of HE methods. Another limitation occurs when a few adjacent luminance levels occupy dominant areas in an image; this leads to quantum jump in CDF so which produce unnatural resultant images. These two limitations are considered to be the major limitations of HE based enhancement technique. Although various methods have been proposed to overcome these limitations, they are still unsatisfactory from the viewpoint of robustness. Here proposing a new method to overcome these problems. In this method apply a wavelet image decomposition to separate an image into several frequency components in the spatial domain, to effectively reduce the quantum jump the proposed contrast enhancement algorithm has two key strategies of boosting noticeable minor areas and slantwise clipping bins in the histogram. And for preserving the local information here uses Laplacian pyramid decomposition. These strategies result in a well-balanced mapping function. The proposed method features robust enhancement without over-enhancement or severe failure.

Keywords: Contrast Enhancement, Histogram Equalization, Laplacian Pyramid, Sigmoid Function, Wavelet Decomposition

Article published in International Journal of Current  Engineering  and Technology, Vol.4,No.2 (April- 2014)