Photographs Alignment and High Dynamic Range Image Composition Based on Varying Exposure Levels

Abstract

An approach is proposed in this paper for aligning the photographs, which are taken with varying amounts of exposure towards the same scene, and fusing into a high dynamic range image. Firstly, the median threshold images of the photograph-sequence are computed, and their image pyramids are constructed using multi-scale techniques. Comparing the image pyramids level-by-level completes shift-alignments of photographs. Based on the shift-alignments, rotation-alignments of photographs can be achieved. According to least-squares principle, the response function curve of the imaging process can be recovered; the mapping relationship between pixel values and exposures is acquired with the sample pixels from the aligned photograph-sequence. A satisfactory high dynamic range image can be constructed from the photographs. The experimental results show that the proposed approach is fast and efficacious.