An Entropy-Based Inverse Tone Mapping Operator with Improved Color Accuracy for High Dynamic Range Applications

Abstract

Conversion of existing image and video content to High Dynamic Range (HDR) using inverse Tone Mapping Operators (iTMOs) is expected to open new market opportunities for studios and content owners. One of the issues facing iTMOs arises from the fact that changing the input Standard Dynamic Range (SDR) luminance to HDR results in color shifts, regardless of the color space or gamut that the operation takes place, requiring the use of an efficient color restoration method. Therefore, maintaining the color accuracy between the input SDR and output HDR content is of high importance in designing iTMOs. In this paper, we propose an iTMO capable of maintaining the color accuracy between the original SDR and the resulting HDR output, while at the same time providing a good balance between the overall brightness and contrast in the HDR content. The results of our subjective evaluation demonstrate that the colors of the generated HDR content closely match those of the original SDR input, outperforming the existing state-of-the-art iTMOs and making the resulting HDR look natural and more appealing to the viewers.