NAME
normtiff - tone-map and convert RADIANCE picture or HDR TIFF to
standard TIFF
SYNOPSIS
normtiff [ options ] input output.tif
DESCRIPTION
Normtiff prepares a Radiance picture or 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.
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 a
high dynamic-range TIFF, the program reports an error and exits.
The following command line options are understood. Since this program
is very similar to pcond(1), several of the switches are identical.
-b Toggle 8-bit black and white (grayscale) TIFF output. If the
input is a grayscale TIFF, this switch is automatically
selected. Otherwise, the output defaults to 24-bit RGB.
-z Output LZW-compressed TIFF (smaller file).
-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.
-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.
-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.
-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.
-u Ldmax 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.
-d Lddyn 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.
-p xr yr xg yg xb yb xw yw
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.
-g gamma 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
To convert a RADIANCE picture to an 8-bit grayscale TIFF:
normtiff -b scene.hdr sceneb.tif
To condition a high dynamic-range TIFF for a particular film recorder
with known color primaries, dynamic range and gamma response:
pcond -d 50 -g 2.5 -p .580 .340 .281 .570 .153 .079 .333 .333
orig.tif filmrgb.tif
To simulate human visual response on a monitor with known maximum
luminance:
normtiff -h -u 80 scene.hdr sceneh.tif
REFERENCE
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.
http://positron.cs.berkeley.edu/gwlarson/pixformat/
AUTHOR
Greg Ward Larson
ACKNOWLEDGMENT
This work was supported by Silicon Graphics, Inc.
SEE ALSO
getinfo(1), pcond(1), pflip(1), pvalue(1), protate(1), ra_xyze(1),
rpict(1), ximage(1)