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Entropy and Contrast Enhancement of Infrared Thermal Images Using the Multiscale Top-Hat Transform

Facultad Politécnica, Universidad Nacional de Asunción, San Lorenzo 2160, Paraguay
Division of Computer Science, Universidad Pablo de Olavide, ES-41013 Seville, Spain
Author to whom correspondence should be addressed.
Entropy 2019, 21(3), 244;
Received: 29 December 2018 / Revised: 20 February 2019 / Accepted: 25 February 2019 / Published: 4 March 2019
(This article belongs to the Special Issue Entropy in Image Analysis)
PDF [2091 KB, uploaded 4 March 2019]


Discrete entropy is used to measure the content of an image, where a higher value indicates an image with richer details. Infrared images are capable of revealing important hidden targets. The disadvantage of this type of image is that their low contrast and level of detail are not consistent with human visual perception. These problems can be caused by variations of the environment or by limitations of the cameras that capture the images. In this work we propose a method that improves the details of infrared images, increasing their entropy, preserving their natural appearance, and enhancing contrast. The proposed method extracts multiple features of brightness and darkness from the infrared image. This is done by means of the multiscale top-hat transform. To improve the infrared image, multiple scales are added to the bright areas and multiple areas of darkness are subtracted. The method was tested with 450 infrared thermal images from a public database. Evaluation of the experimental results shows that the proposed method improves the details of the image by increasing entropy, also preserving natural appearance and enhancing the contrast of infrared thermal images. View Full-Text
Keywords: discrete entropy; infrared images; low contrast; multiscale top-hat transform discrete entropy; infrared images; low contrast; multiscale top-hat transform

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Mello Román, J.C.; Vázquez Noguera, J.L.; Legal-Ayala, H.; Pinto-Roa, D.P.; Gomez-Guerrero, S.; García Torres, M. Entropy and Contrast Enhancement of Infrared Thermal Images Using the Multiscale Top-Hat Transform. Entropy 2019, 21, 244.

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