Infrared (IR) thermal cameras are often used to measure surfaces temperature and heat loads in environments with extreme operating conditions. IR devices had always revealed to be useful in nuclear fusion experiments, especially to monitor the thermal behavior of plasma-facing components (PFCs). The main drawback in using IR thermography relies on the fact that measurements are always affected by an error due to the different emissivity of the materials pointed by the IR camera with respect to the ideal black body. As a consequence, an image processing stage is required in order to correct raw data. Furthermore, in the specific conditions at which PFCs operate, unwanted phenomena, such as oxidation, deviates the actual emissivity values from the tabulated ones. Therefore, specific strategies to cope with these issues must be developed. In Frascati Tokamak Upgrade (FTU), two cooled liquid metal limiter devices have been investigated: a cooled liquid lithium limiter (CLL) and a liquid tin limiter (TLL). In this paper, we introduce a software tool for the automatic correction of the emissivity error exploiting a-priori knowledge on the specific metal. The output of the procedure is the definition of suitable correction maps based on the detection of the metal melting point. © 2017 IOP Publishing Ltd.