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Abstract

High Dynamic Range (HDR) images capture the full range of luminance
present in real world scenes, and unlike Low Dynamic Range (LDR)
images, can simultaneously contain detailed information in the
deepest of shadows and the brightest of light sources. For display
or aesthetic purposes, it is often necessary to perform tone
mapping, which creates LDR depictions of HDR images at the cost of
contrast information loss. The purpose of this work is two-fold: to
analyze a displayed LDR image against its original HDR counterpart
in terms of perceived contrast distortion, and to enhance the LDR
depiction with perceptually driven colour adjustments to restore the
original HDR contrast information. For analysis, we present a novel
algorithm for the characterization of tone mapping distortion in terms
of observed loss of global contrast, and loss of contour and texture
details. We classify existing tone mapping operators accordingly.
We measure both distortions with perceptual metrics that enable the
automatic and meaningful enhancement of LDR depictions. For image
enhancement, we identify artistic and photographic colour techniques
from which we derive adjustments that create contrast with colour.
The enhanced LDR image is an improved depiction of the original HDR
image with restored contrast
information.