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.TH NORMTIFF 1 2/25/99 RADIANCE
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.SH NAME
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normtiff - tone-map and convert RADIANCE picture or SGILOG TIFF to RGB TIFF
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.SH SYNOPSIS
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.B normtiff
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[
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.B options
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]
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.B input
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.B output.tif
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.SH DESCRIPTION
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.I Normtiff
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prepares a Radiance picture or SGILOG (high dynamic range) TIFF
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for output to a display or hard copy device.
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If the dynamic range of the scene exceeds that of the display (as is
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usually the case),
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.I normtiff
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will compress the dynamic range of the picture such that both
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dark and bright regions are visible.
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In addition, certain limitations in human vision may be mimicked in
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order to provide an appearance similar to the experience one might
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have in the actual scene.
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.PP
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Output is always an uncompressed RGB TIFF, which must be named
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on the command line along with the input file.
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If the input file has a ".tif" or ".tiff" extension,
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.I normtiff
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attempts to read it as a TIFF.
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Otherwise,
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.I normtiff
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first tries opening it as a RADIANCE picture, only opening it
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as a TIFF if it fails header inspection.
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(See the
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.I getinfo(1)
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program.)\0
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If the input is neither a RADIANCE picture nor an SGILOG-encoded TIFF,
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the program reports an error and exits.
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.PP
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The following command line options are understood.
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Since this program is very similar to
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.I pcond(1),
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several of the switches are identical.
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.TP 10n
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.BR -b
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Toggle 8-bit black and white (grayscale) TIFF output.
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If the input is a 16-bit SGILOG luminance-only TIFF, this switch is
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automatically selected.
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Otherwise, the output defaults to 24-bit RGB.
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.TP
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.BR -h
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Mimic human visual response in the output.
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The goal of this process is to produce output that correlates
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strongly with a person's subjective impression of a scene.
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This switch turns on both the
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.I \-s
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and
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.I \-c
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switches, described below.
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.TP
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.BR -s
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Toggle the use of the human contrast sensitivity function in determining the
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exposure for the image.
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A darker scene will have relatively lower exposure with lower
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contrast than a well-lit scene.
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.TP
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.BR -c
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Toggle mesopic color correction.
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If parts of the image are in the mesopic or scotopic range where
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the cone photoreceptors lose their efficiency, this switch will
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cause a corresponding loss of color visibility in the output and a
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shift to a scotopic (blue-dominant) response function.
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.TP
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.BR -l
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Toggle the use of a linear response function versus the standard dynamic
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range compression algorithm.
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This may make some parts of the resulting image too
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dark or too bright to see.
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.TP
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.BI -u \ Ldmax
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Specifies the top of the luminance range for the target output device.
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That is, the luminance (in candelas/m^2) for an output pixel value
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of (R,G,B)=(255,255,255).
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This parameter affects tone mapping only when the
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.I \-s
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switch is on.
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The default value is 100 cd/m^2.
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.TP
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.BI -d \ Lddyn
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Specifies the dynamic range for the target output device, which is
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the ratio of the maximum and minimum usable display luminances.
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The default value is 32, which is typical for CRT monitors.
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.TP
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.BI -p " xr yr xg yg xb yb xw yw"
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Specifies the RGB primaries for the target output device.
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These are the 1931 CIE (x,y) chromaticity values for red, green,
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blue and white, respectively.
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.TP
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.BI -g \ gamma
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Specifies the output device gamma correction value.
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The default value is 2.2, which is appropriate for most CRT monitors.
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(A value of 1.8 is common in color prepress and color printers.)\0
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.SH EXAMPLES
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To convert a RADIANCE picture to an 8-bit grayscale TIFF:
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.IP "" .2i
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normtiff -b scene.pic sceneb.tif
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.PP
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To condition an SGILOG TIFF for a particular film recorder with
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known color primaries, dynamic range and gamma response:
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.IP "" .2i
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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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.PP
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To simulate human visual response on a monitor with known maximum luminance:
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.IP "" .2i
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normtiff -h -u 80 scene.pic sceneh.tif
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.SH REFERENCE
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Greg Ward Larson, Holly Rushmeier, Christine Piatko,
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``A Visibility Matching Tone Reproduction Operator for High Dynamic Range
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Scenes,''
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.I "IEEE Transactions on Visualization and Computer Graphics",
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December 1997.
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.PP
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http://positron.cs.berkeley.edu/gwlarson/pixformat/
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.SH AUTHOR
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Greg Ward Larson
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.SH ACKNOWLEDGMENT
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This work was supported by Silicon Graphics, Inc.
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.SH "SEE ALSO"
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getinfo(1), pcond(1), pflip(1),
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pvalue(1), protate(1), ra_xyze(1), rpict(1), ximage(1)
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