Color and Contrast Enhancement by Controlled Piecewise Affine Histogram Equalization

This paper presents a simple contrast enhancement algorithm based on histogram equalization (HE). The proposed algorithm performs a piecewise affine transform of the intensity levels of a digital image such that the new histogram function will be approximately uniform (as with HE), but where the stretching of the range is locally controlled to avoid brutal noise enhancement. We call this algorithm Piecewise Affine Equalization (PAE). Several experiments show that, in general, the new algorithm improves HE results. Source Code The proposed algorithm has been implemented in ANSI C. The source code, the code documentation, and the online demo are accessible from the web page of this article1.