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Modern InfraRed (IR) cameras have High Dynamic Range (HDR) and excellent sensitivity. They collect images using a
number of bits much higher than the 8-bits used in displays or than those effectively perceived by the human visual
system. In IR imagery, suitable techniques to display HDR images are therefore required in order to improve the
visibility of the details while preserving the global perception of the scene. Visualization of HDR images has already
been widely studied for visible-light images. In the IR framework only a few works have been proposed which tightly
depend on the operating scenario and on the application of interest. In most cases such works have been obtained by
modifications of methods proposed for visible light images rather than by developing visualization techniques taking into account the specific mechanism of IR image formation. In the literature, the techniques developed to display HDR
images are mainly based on two approaches: contrast enhancement (CE)-oriented techniques and dynamic range
compression (DRC)-oriented techniques. The former operate on image contrast to increase the perceptibility of details.
The latter reduce the signal dynamic thus attenuating the large-scale intensity changes that do not contain relevant
information. In addition, some of the proposed methods for HDR take advantage of both the approaches. In this work, a DRC approach is considered for visualization of HDR-IR images of maritime scenarios. A new method is presented that exploits clustering information and maps the output image according to the information content of each cluster by means of a suitable weighting function. The effectiveness of the presented technique is analyzed using IR images of a maritime scenario acquired in two different case studies. Moreover, the output images obtained with the proposed method are compared with those given by techniques previously proposed for visualization of IR images. The results show the effectiveness of the proposed technique in terms of details enhancement, robustness against the horizon effect and presence of very warm objects.
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