A contrast enhancement method using dynamic range separate histogram equalization

In this paper, a contrast enhancement method using dynamic range separate histogram equalization (DRSHE) is proposed. Histogram equalization (HE) method is widely used for contrast enhancement. However, HE is not suitable for consumer electronic products directly because it may cause side-effects such as washed out appearance and false contouring due to the significant change in brightness. DRSHE separates the dynamic range of histogram into k parts and resizes the grayscale range based on its area ratio. Then intensities of histogram are uniformly redistributed in resized grayscale range. DRSHE uses weighted average of absolute color difference (WAAD) in order to emphasize the edge of original image and moderate the histogram variation effectively. We introduced a linear adaptive scale factor to reduce excessive changes in brightness. The experimental results show that DRSHE suppresses unintended changes in brightness and preserves naturalness of the original image compared with conventional methods.