A Practical and Efficient Contrast Enhancement Method

The principle of image enhancement is based on increasing the contrast between adjacent pixels, which enables enabling viewers to visually perceive images with more details in the textures and edges. Many contrast enhancement methods have been proposed to improve the quality of images and most of them are based on histogram equalization (HE). This paper proposes a contrast enhancement technique modified by previous study to keep the brightness of the enhanced image. The implementation of the modified version is also simplified. The proposed method is not only suitable for the requirement of video images, the adjustment for clear display made by viewers, but also simplified for the real world. In the hardware implementation, the proposed method can reach 43.6 MSps(million sample per second) which is 3.23 times faster than the demand of SDTV NTSC 720×480i specification and 1.61 times faster than the demand of EDTV NTSC 720×480p specification. Moreover, for evaluating the efficiency of the related techniques by more fairly and complete observations, the paper makes comprehensive evaluations based on several subjective and objective evaluation metrics for various famous contrast enhancement techniques. The several important issues about the efficiency characters are also included in this paper.