The fundamental reason of contrast enhancement is to bring out detail that is hidden in an image that is covered up in a picture or to expand contrast in a low contrast picture. This paper presents a literature survey on some of the image Enhancement techniques for improving images like histogram equalization, global histogram equalization, bi-histogram equalization, dualistic sub-image histogram equalization, Spatial Domain Method and Frequency Domain Method etc. The overall objective of this paper is to evaluate the short comings in earlier techniques of image enhancement.

In digital image processing, image enhancement contributes a vital role. It is a procedure used for the modification of digital images. It is one of the essential vision applications which have ability to improve the visibility of images. It is used to enhance the superiority of poor images and low quality images into the high-quality images so that images can be much clearer for human observation. The key purpose of this dissertation has been to explore and verify the limitations of the existing image enhancement procedures. Several techniques have been predictable so far to enhance the superiority of the digital images. To enhance the photograph quality, image enhancement improves and bound various facts available in the input image. Several procedures have been projected so far for improving the satellite image enhancement; which may decrease the intensity of the original satellite image. To overcome this problem we have introduced an integrated approach. To evaluate the performance of dominant brightness level based image enhancement technique, several parameters has been used like Bit Error Rate, Cross Correlation and Average Difference.

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