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normtiff (1)
NAME
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normtiff - tone-map and convert RADIANCE picture or SGILOG TIFF to RGB TIFF |
SYNOPSIS
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normtiff [ options ] input
output.tif |
DESCRIPTION
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Normtiff prepares a Radiance picture or SGILOG (high
dynamic range) TIFF for output to a display or hard copy
device. If the dynamic range of the scene exceeds that of
the display (as is usually the case), normtiff will
compress the dynamic range of the picture such that both
dark and bright regions are visible. In addition, certain
limitations in human vision may be mimicked in order to
provide an appearance similar to the experience one might
have in the actual scene. |
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Output is always an uncompressed RGB TIFF, which must be
named on the command line along with the input file. If the
input file has a ".tif" or ".tiff"
extension, normtiff attempts to read it as a TIFF.
Otherwise, normtiff first tries opening it as a
RADIANCE picture, only opening it as a TIFF if it fails
header inspection. (See the getinfo(1) program.) If
the input is neither a RADIANCE picture nor an
SGILOG-encoded TIFF, the program reports an error and
exits. |
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The following command line options are understood. Since
this program is very similar to pcond(1), several of
the switches are identical. |
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-b Toggle 8-bit black and white (grayscale) TIFF
output. If the input is a 16-bit SGILOG luminance-only TIFF,
this switch is automatically selected. Otherwise, the output
defaults to 24-bit RGB. |
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-h Mimic human visual response in the output. The
goal of this process is to produce output that correlates
strongly with a person's subjective impression of a scene.
This switch turns on both the -s and -c
switches, described below. |
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-s Toggle the use of the human contrast sensitivity
function in determining the exposure for the image. A darker
scene will have relatively lower exposure with lower
contrast than a well-lit scene. |
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-c Toggle mesopic color correction. If parts of the
image are in the mesopic or scotopic range where the cone
photoreceptors lose their efficiency, this switch will cause
a corresponding loss of color visibility in the output and a
shift to a scotopic (blue-dominant) response
function. |
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-l Toggle the use of a linear response function
versus the standard dynamic range compression algorithm.
This may make some parts of the resulting image too dark or
too bright to see. |
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Specifies the top of the luminance range for the target
output device. That is, the luminance (in candelas/m^2) for
an output pixel value of (R,G,B)=(255,255,255). This
parameter affects tone mapping only when the -s
switch is on. The default value is 100 cd/m^2. |
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Specifies the dynamic range for the target output device,
which is the ratio of the maximum and minimum usable display
luminances. The default value is 32, which is typical for
CRT monitors. |
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-p xr yr xg yg xb yb xw yw |
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Specifies the RGB primaries for the target output device.
These are the 1931 CIE (x,y) chromaticity values for red,
green, blue and white, respectively. Usually, the white
value is set to (.333,.333) to avoid color balance problems
in the display. The default primaries match sRGB space with
a neutral white balance. |
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Specifies the output device gamma correction value. The
default value is 2.2, which is appropriate for most CRT
monitors. (A value of 1.8 is common in color prepress and
color printers.) |
EXAMPLES
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To convert a RADIANCE picture to an 8-bit grayscale
TIFF: |
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normtiff -b scene.pic sceneb.tif |
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To condition an SGILOG TIFF for a particular film recorder
with known color primaries, dynamic range and gamma
response: |
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pcond -d 50 -g 2.5 -p .580 .340 .281 .570 .153 .079 .333
.333 orig.tif filmrgb.tif |
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To simulate human visual response on a monitor with known
maximum luminance: |
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normtiff -h -u 80 scene.pic sceneh.tif |
REFERENCE
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Greg Ward Larson, Holly Rushmeier, Christine Piatko, ``A
Visibility Matching Tone Reproduction Operator for High
Dynamic Range Scenes,'' IEEE Transactions on
Visualization and Computer Graphics , December
1997. |
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http://positron.cs.berkeley.edu/gwlarson/pixformat/ |
AUTHOR
ACKNOWLEDGMENT
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This work was supported by Silicon Graphics,
Inc. |
SEE ALSO
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