Segmentation-based optimized tone mapping for high dynamic range image and video coding

A core part of the state-of-the art high dynamic range (HDR) image and video compression methods is the tone mapping operation to convert the visible luminance range into the finite bit depths that can be supported by the current video codecs. These conversions are until now optimized to provide backward compatibility to the existing low dynamic range (LDR) displays. However, a direct application of these methods for the emerging HDR displays can result in a loss of details in the bright and dark regions of the HDR content. In this paper, we overcome this limitation by designing a tone mapping operation which handles the bright and dark regions separately. The proposed method first finds the optimal segmentation of the HDR image into two parts, namely dark and bright regions, and then designs the optimal tone mapping for each region in terms of the mean square error between the logarithm of the luminance values of the original and reconstructed HDR content (HDR-MSE). The results indicate the superiority of the proposed method over the state-of-the art HDR coding methods.