Fast Inverse Tone Mapping Based on Reinhard's Global Operator with Estimated Parameters

Abstract

This paper proposes a new inverse tone mapping operator (TMO) with estimated parameters. The proposed inverse TMO is based on Reinhard's global operator which is a well-known TMO. Inverse TM operations have two applications: generating an HDR image from an existing LDR one, and reconstructing an original HDR image from the mapped LDR image. The proposed one can be applied to both applications. In the latter application, two parameters used in Reinhard's TMO, i.e. the key value α regarding brightness of a mapped LDR one and the geometric mean $\overline{L}_w$ of an original HDR one, are generally required for carrying out the Reinhard based inverse TMO. In this paper, we show that it is possible to estimate $\overline{L}_w$ from α under some conditions, while α can be also estimated from $\overline{L}_w$, so that a new inverse TMO with estimated parameter is proposed. Experimental results show that the proposed method outperforms conventional ones for both applications, in terms of high structural similarities and low computational costs.