ADAPTIVE NEIGHBORHOOD EXTENDED CONTRAST ENHANCEMENT AND ITS MODIFICATIONS

A new technique for contrast enhancement, namely adaptive neighborhood extended contrast enhancement, and several original modifications on the same are proposed. Developing from the adaptive contrast enhanceme nt algorithm of Beghdadi and Negrate (Comput. Vision Graphics Image Pr ocess. 46, 1989, 162-174), and the adaptive neighborhood histogram equ alization algorithm of Paranjape et al. (CVGIP Graphical Models Image Process. 54(3), 1992, 259-267), the above techniques have been evolved in order to make image enhancement more adaptive and context sensitiv e. The adaptive neighborhood extended contrast enhancement algorithm, without its other modifications, only combines the features of these t wo existing algorithms. This algorithm can be used for both image enha ncement and de-enhancement and can also be combined with existing proc edures such as power variation. To make the algorithm computationally efficient, the computationally efficient adaptive neighborhood extende d contrast enhancement procedure is proposed. This modification achiev es significant computational speedup without much loss of image qualit y. The adaptive neighborhood definition extended contrast enhancement procedure is next proposed in order to make the algorithm further adap tive by making its performance independent of its most sensitive param eter. This procedure achieves better identification of different gray level regions by an analysis of the histogram in the locality of every pixel in the image. The experimental results aptly demonstrate the ef ficacy of the procedure. This technique can Ire well applied to other contrast enhancement algorithms for improvement of the quality of the enhanced image. Finally, a correction mechanism called repulsion corre ction is evolved to correct for a specific inability of contrast enhan cement algorithms in separating adjacent regions of nearly equal brigh tness from each other when surrounded by a very large, brighter or dar ker region. (C) 1995 Academic Press, Inc.