Unsharp masking, countershading and halos: Enhancements or artifacts?

Matthew Trentacoste, Rafał Mantiuk, Wolfgang Heidrich, Florian Dufrot

Research output: Contribution to journalConference articlepeer-review

29 Scopus citations


Countershading is a common technique for local image contrast manipulations, and is widely used both in automatic settings, such as image sharpening and tonemapping, as well as under artistic control, such as in paintings and interactive image processing software. Unfortunately, countershading is a double-edged sword: while correctly chosen parameters for a given viewing condition can significantly improve the image sharpness or trick the human visual system into perceiving a higher contrast than physically present in an image, wrong parameters, or different viewing conditions can result in objectionable halo artifacts. In this paper we investigate the perception of countershading in the context of a novel mask-based contrast enhancement algorithm and analyze the circumstances under which the resulting profiles turn from image enhancement to artifact for a range of parameters and viewing conditions. Our experimental results can be modeled as a function of the width of the countershading profile. We employ this empirical function in a range of applications such as image resizing, view dependent tone mapping, and countershading analysis in photographs and works of fine art.

Original languageEnglish (US)
Pages (from-to)555-564
Number of pages10
JournalComputer Graphics Forum
Issue number2
StatePublished - 2012
Externally publishedYes
Event33rd Annual Conference on European Association for Computer Graphics, EUROGRAPHICS 2012 - Cagliari, Sardinia, Italy
Duration: May 13 2012May 18 2012

ASJC Scopus subject areas

  • Computer Graphics and Computer-Aided Design


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