Modified Dynamic Histogram Equalization For Image Enhancement in Gray-scale Images

摘要

To improve the quality of digital images captured in low light environment from consumer electronics devices like cell phone cameras, Modified Dynamic Histogram Equalization (MDHE) is proposed. Initially, the proposed method divides the histogram into two sub-histograms based on median. Then 2nd subhistogram is further divided into two sub-histograms based on median of it. The resultant sub-histograms are clipped according to the mean of the intensity occurrence of the input image independently. The new dynamic range is allocated to each sub-histogram. The first sub-histogram is equalized independently using Global Histogram Equalization (GHE) method. GHE is found the better enhancement for lower gray-levels and suffers over-enhancement problem in higher gray-level. The proposed method utilizes the advantages of both GHE and QDHE. This method utilizes GHE for enhancing lower gray-levels and QDHE for enhancing higher gray-levels. Simulation results show that the proposed method yields better quality images in terms of Discrete Entropy value compared with other conventional methods.