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Proceedings Paper

Nonlinear mapping for dynamic range compression in digital images
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Paper Abstract

The dynamic range of an image is defined as the ratio between the maximum and minimum luminance value it contains. This value in real images can be several thousands or even millions, whereas the dynamic range of consumer imaging devices rarely exceeds 100; therefore some processing is needed in order to display a high dynamic range image correctly. Global operators map each pixel individually with the same nonlinear function; local operators use spatially-variant functions in order to achieve a higher quality. The lower computational cost of global operators makes them attractive for real-time processing; the nonlinear mapping can however attenuate the image details. In this paper we define an expression which gives a quantitative measure of this artifact, and compare the performance of some commonly used operators. We show that a modified logarithm we propose has a satisfactory performance for a wide class of images, and has a theoretical justification based on some properties of the human visual system. We also introduce a method for the automatic tuning of the parameters of our system, based on the statistics of the input image. We finally compare our method with others proposed in the literature.

Paper Details

Date Published: 27 February 2007
PDF: 11 pages
Proc. SPIE 6497, Image Processing: Algorithms and Systems V, 64970M (27 February 2007); doi: 10.1117/12.705369
Show Author Affiliations
Gabriele Guarnieri, Univ. of Trieste (Italy)
Sergio Carrato, Univ. of Trieste (Italy)
Giovanni Ramponi, Univ. of Trieste (Italy)


Published in SPIE Proceedings Vol. 6497:
Image Processing: Algorithms and Systems V
Jaakko T. Astola; Karen O. Egiazarian; Edward R. Dougherty, Editor(s)

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