An inverse tone mapping operator based on Reinhard's global operator

A number of inverse tone mapping operators (TMOs) for dynamic range expansion have been proposed due to the need to visualize low dynamic range (LDR) images on high dynamic range (HDR) devices. This paper proposes a novel inverse TMO, which enables to generate HDR images from LDR ones, not only without using any specific parameters but also at low computing costs. Furthermore, the inverse TMO has a new characteristic when an LDR image is mapped from an HDR one by Reinhard's global operator. In the case, the HDR image reconstructed by the proposed method without parameters can be remapped into the same image as that remapped from an HDR one reconstructed with parameters. Experimental results show that the proposed inverse tone mapping (TM) operation can be carried out, while keeping better structural similarity and lower computing cost than conventional methods.