Multi-Scale Decomposition Tone Mapping Using Guided Image Filter

Abstract

Dynamic range is the ratio between the brightest and the darkest luminance values. The dynamic range visible to human vision can reach 〖10〗^5 and the dynamic range of high dynamic range (HDR) image can be between 〖10〗^4–〖10〗^5 while ordinary low dynamic range (LDR) images are only 〖10〗^2–〖10〗^3. Since the higher dynamic range images contain more information, HDR images tend to have a stunning visual effect. However, since the dynamic range of ordinary monitors is too low to display HDR contents, a tone mapping process is needed. The tone mapping is a method used in HDR image processing which can compress high dynamic range images to a low dynamic range. Commonly, the tone mapping technology uses an edge-preserving filter to decompose the original image. Guided image filter (GIF) is one of the edge-preserving filters which has an excellent effect. The GIF is used to divide an image into a base layer and a detail layer, then the range of the detail layer is reduced with a compression function to enhance the detail information of the image. However, in most cases, an image includes the detail and edge information in different scales. That is to say, it is difficult to represent all detail features under a certain scale, and a single-scale image decomposition method is not free from artifacts around edges. To solve the problems, the multi-scale image decomposition method is proposed in this thesis. It utilizes the detail layers of several scales to determine how much edge is preserved. Experiment results show that the proposed algorithm has better performance in preserving edge compared to conventional algorithms.