A Comprehensive Survey on Image Contrast Enhancement Techniques in Spatial Domain

Image enhancement is essential for any image processing applications. The objective of image enhancement is to reveal the hidden information which is not available for the purview of the observer due to the presence of low and poor contrast during image acquisition. The quality of the image can be raised up by increasing the contrast. Contrast enhancement has found a prominent application in various fields such as medical, satellite imaging systems owing to its better visibility of the features. In this paper, a comprehensive survey on different contrast enhancement techniques exclusively on spatial domain is presented and compared. The survey illustrates that brightness preservation, entropy preservation, structural information loss etc., are to be catered during contrast enhancement. To validate the algorithm in terms of both qualitative and quantitative means, the researchers have used various performance measures. Among all the performance measures, entropy finds the benchmark for evaluation of the algorithms. Different databases are used by researchers to analyse the performance of their algorithms, where as USC-SIPI database finds prominence in usage.