Simple tone curves: theory and applications

Bennett, James and Finlayson, Graham D. (2026) Simple tone curves: theory and applications. The Visual Computer, 42 (8). pp. 1-18. ISSN 0178-2789

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Abstract

A single tone curve that remaps the brightnesses of each image pixel is a simple and widely deployed way to enhance an image. Tone curves might be crafted by individual users or determined algorithmically in camera processing pipelines. The precise shape of the tone curve is not a priori strongly constrained, other than it is usually limited to increasing functions of brightness. In this paper, we constrain the shape further and define a tone curve to be simple if it has no or one inflexion point. With respect to our representation, wiggly tone curves have several inflexion points and are deemed to be complex. A key contribution of our work is to show how we can best approximate a complex curve with a simple counterpart. For the MIT-Adobe FiveK dataset, comprising thousands of images that are tone-adjusted by photographic experts, we calculate corresponding simple tone curve adjusted images. Using objective similarity metrics, we find that simple curves deliver equally good image enhancement. In terms of preference experiments, simple curves deliver slightly preferred images compared to complex counterparts. Similar results are reported for a second smaller underwater image dataset.

Item Type:	Article
Additional Information:	Data Availability The MIT-Adobe FiveK dataset is available at https://doi.org/10.1109/CVPR.2011.5995413. The anonymised data collected from the psychophysical pairwise preference experiment are available from the corresponding author on reasonable request. The Gardline dataset was used under licence and is not publicly available. Acknowledgements The experiments were carried out on the High Performance Computing Cluster supported by the Research and Specialist Computing Support service at the University of East Anglia.
Uncontrolled Keywords:	image enhancement,psychophysical experiment,quadratic programming,tone curves,tone mapping,software,computer vision and pattern recognition,computer graphics and computer-aided design ,/dk/atira/pure/subjectarea/asjc/1700/1712
Faculty \ School:	Faculty of Science Faculty of Science > School of Computing Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Colour and Imaging Lab
Related URLs:	https://www.scopus.com/pages/publication...
Depositing User:	LivePure Connector
Date Deposited:	04 Jun 2026 08:32
Last Modified:	08 Jun 2026 11:28
URI:	https://ueaeprints.uea.ac.uk/id/eprint/103276
DOI:	10.1007/s00371-026-04505-y

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