Premium
Unsharp Masking, Countershading and Halos: Enhancements or Artifacts?
Author(s) -
Trentacoste Matthew,
Mantiuk Ratal,
Heidrich Wolfgang,
Dufrot Florian
Publication year - 2012
Publication title -
computer graphics forum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.578
H-Index - 120
eISSN - 1467-8659
pISSN - 0167-7055
DOI - 10.1111/j.1467-8659.2012.03056.x
Subject(s) - computer science , computer vision , tone mapping , artificial intelligence , unsharp masking , sharpening , contrast (vision) , artifact (error) , image (mathematics) , context (archaeology) , masking (illustration) , human visual system model , high dynamic range , image processing , computer graphics (images) , dynamic range , art , paleontology , visual arts , biology
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.