GVU Technical Report Number:
GIT-GVU-98-22
Title:
Two Methods for Display of High Contrast Images
Authors:
Jack Tumblin
Jessica K. Hodgins
Brian K. Guenter
Abstract:
High contrast images are common in night scenes and other scenes that
include dark shadows and bright light sources. These scenes are difficult
to display because their contrasts greatly exceed the range of most
display devices for images. As a result, the image contrasts are
compressed or truncated, obscuring subtle textures and details. Humans
view and understand high contrast scenes easily, ``adapting'' their visual
response to avoid compression or truncation with no apparent loss of
detail. By imitating some of these visual adaptation processes, we
developed two methods for the improved display of high contrast images.
The first builds a display image from several layers of lighting and
surface properties. Only the lighting layers are compressed, drastically
reducing contrast while preserving much of the image detail. This method
is practical only for synthetic images where the layers can be retained
from the rendering process. The second method interactively adjusts the
displayed image to preserve local contrasts in a small ``foveal''
neighborhood. Unlike the first method, this technique is usable on any
image and includes a new tone reproduction operator. Both methods use a
sigmoid function for contrast compression. This function has no effect
when applied to small signals but compresses large signals to fit within
an asymptotic limit. We demonstrate the effectiveness of these approaches
by comparing processed and unprocessed images.
Keywords:
High contrast images, imaging techniques
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