Improved Laplacian Model for Tone Mapping of HDR Image

The tone mapping of HDR (high dynamic range) images is one of the hot topics in image processing, which is used to handle the problem that regular equipments cannot efficiently display HDR images.However, current tone mapping methods cannot accurately display image content such as losing details and blurring weak edges.This paper proposes a new tone mapping method by improving the Laplacian pyramid model.Firstly, the Gaussian pyramid of the input image is computed by using down-sample and filter to reduce noise.Then, the strong edges, weak edges, and details of each Gaussian pyramid layer are separated via restricting the pixel numbers of strong edges.Then different mapping function is defined for each Gaussian pyramid layer, and is used to implement pixelwise mapping on each layer to enhance the comparison of details and weak edges and preserving strong edges.Based on the mapped Gaussian pyramid, the corresponding Laplacian pyramid is computed to record the comparison changes of each layer.Finally, the result image is constructed from bottom to top based on Laplacian pyramid.Compared with existing tone mapping methods, based on the subjective and objective assessments, our method can display HDR images more clearly and accurately by enhancing details, weak edges and avoiding gradient reverse.