<title>Region-based histogram specification for dynamic range expansion</title>

In this paper, we propose a method of region based histogram specification resulting dynamic range expansion effect. Main goal of this paper is enhancement of the image captured in back light condition, in which the captured image contains tow extremely contrasted regions simultaneously. The proposed method has two steps. The first is region segmentation in the spatial domain by using threshold values derived from the histogram domain. The second step is execution of independent histogram modification for the segmented regions. The histogram modification for each region is similar to typical histogram equalization except the interval to be histogram equalized. The resulting regionally histogram specified image can be obtained by combining the results of the previous steps. The proposed segmentation algorithm has an advantage in computational cost in that it can be performed with simple neighborhood operation by using the thresholding intensity level derived fast from histogram domina. The proposed algorithm shows better result than the typical histogram equalization by referring to specific region of interest to be enhanced.