Two-layer pyramid-based blending method for exposure fusion

Multi-exposure fusion is a technique used to generate a high-dynamic-range image without calculating the camera response function and without compressing its ranges with the tone mapping process. There are many schemes for fusing multi-exposure images. One of the famous schemes is the pyramid-based blending, which fuses multi-exposure images together based on the concept of multi-resolution blending. The computational time of this method is fast, and the resulting image is satisfying. However, in some cases, the pyramid-based blending method has a trade-off between preserving local areas and the quality in terms of smoothness boundaries. To solve this trade-off, we propose a new pyramid-based blending scheme, called the two-layer pyramid-based blending method for multi-exposure fusion. We found that, for some sets of input images, we have to generate a virtual photograph and add it into those sets. Thus, we first propose a criterion for adding the virtual photograph. Then, we construct a concatenation of two pyramid-based blending methods, in which the resulting images from different levels of the first-layer pyramid-based blending method are used as inputs of the second-layer one. The test results showed that the resulting images were satisfying, and their objective evaluation scores regarding the perceptual image quality and detail-preserving assessment were high, even though they are not highest, compared with those of methods used in our experiments. Also, there is one advantage of the proposed method compared with the others. That is, the proposed method could preserve details in some areas, whereas the other methods could not.