A Comparative Analysis of Adaptive Contrast Enhancement Equalization Techniques
Abstract
Histogram equalization is a most widely used method for contrast enhancement. It is both effective and simple. But the standard histogram equalization many times results in change of brightness of the complete image. Many applications including consumer electronics can’t afford this change in the original brightness of the image. To preserve the original brightness, new contrast enhancement schemes like bi-histogram equalization (BHE), recursive mean-separate histogram equalization (RM.SHE), clipped histogram equalization (CHE) and gaincontrollable clipped histogram equalization (GC-CHE) are introduced [1]. These methods are analysed in this paper, along with existing standard histogram equalization method. The above mentioned schemes not only perform equalization but also preserve the original brightness of the image. The GC-CHE scheme uses controllable gain clipped histogram equalization which takes into account the mean brightness of the image to calculate clipping rate and the clipping threshold. The rate of clipping is controlled adaptively for contrast enhancement which preserves the mean brightness. It is found that under various conditions, the GC-CHE method performs better than the other equalization methods. Index Terms - bi-histogram equalization (BHE), recursive meanseparate histogram equalization (RMSHE), gain-controllable clipped histogram equalization (GC-CHE)
References
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