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.\" RCSid "$Id: ra_t8.1,v 1.2 2003/12/09 15:59:06 greg Exp $"
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.TH RA_T8 1 5/30/95 RADIANCE
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.SH NAME
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ra_t8 - convert RADIANCE picture to/from Targa 8-bit image file
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.SH SYNOPSIS
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.B ra_t8
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[
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.B \-d
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][
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.B \-b
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][
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.B "\-c ncolors"
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][
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.B "\-g gamma"
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][
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.B "\-e +/-stops"
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][
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.B "-n sampfac"
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]
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.B input
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[
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.B output
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]
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.br
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.B ra_t8
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.B \-r
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[
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.B "\-g gamma"
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][
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.B "\-e +/-stops"
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]
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[
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.B input
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[
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.B output
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]
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]
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.SH DESCRIPTION
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.I Ra_t8
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converts between RADIANCE and Targa 8-bit color-mapped image files
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(type 1 in Targa's documentation).
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In the default mode, a RADIANCE picture is converted to a
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color-mapped Targa file of the same horizontal and vertical dimensions with
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8-bits per pixel.
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The
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.I \-d
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option turns off dithering.
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The
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.I \-b
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option converts the image to black and white.
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Only with this option can the input be taken from stdin.
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The
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.I \-c
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option allows fewer than 256 colors.
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The
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.I \-g
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option specifies the exponent used in gamma correction;
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the default value is 2.2.
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An exponent of 1.0 turns gamma correction off.
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The
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.I \-e
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option specifies an exposure compensation in f-stops (powers of two).
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Only integer stops are allowed, for efficiency.
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The
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.I \-n
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option specifies a sampling factor for neural network color
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quantization.
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This value should be between 1 and 80, where 1 takes the longest and
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produces the best results in small areas of the image.
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If no value is given, a faster median cut algorithm is used.
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The
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.I \-r
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option invokes a reverse conversion, from an 8-bit Targa file to
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a RADIANCE picture.
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If the output file is missing, the standard output is used.
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.SH AUTHORS
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Greg Ward
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.br
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Anthony Dekker provided the code for neural network color quantization
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.SH BUGS
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Run-length encoded files can be read but not written with this
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program.
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.SH "SEE ALSO"
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pfilt(1), ra_bmp(1), ra_bn(1), ra_ppm(1), ra_pr(1), ra_pr24(1), ra_t16(1),
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ra_tiff(1), ximage(1)
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