Abstract: Degradation in the captured image quality is a common problem. There are various techniques to enhance the image quality. Some of the techniques used are Contrast Stretching (CS) and Histogram Equalization (HE). These are the basic techniques which don’t provide a significant improvement in enhancing image details. So this arises the need of advancement in these basic algorithms. The papers give a review of the several histogram equalization approaches. The paper also gives a comparative study on the results of implementation of the Adaptive histogram equalization (AHE) and Contrast Limited histogram equalization (CLAHE) and Dynamic histogram equalization (DHE) for gray scale images on FPGA. The proposed system describes Contrast Stretching and Dynamic histogram equalization based algorithms for hardware implementation on FPGA for color images.To validate the algorithms on FPGA, the simulation results are given based on visual analysis of the color input and output image.

Keywords: Histogram Equalization (HE), Dynamic Histogram Equalization (DHE), Adaptive histogram equalization (AHE), Contrast Limited histogram equalization (CLAHE) and Field Programmable Gate Array (FPGA).