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ra_t8 - convert RADIANCE picture to/from Targa 8-bit image
file
ra_t8 [ -d ][ -b ][ -c ncolors ][ -g gamma ][ -e +/-stops ][
-n sampfac ] input [ output ]
ra_t8 -r [ -g gamma ][ -e +/-stops ] [ input [ output ] ]
Ra_t8 converts between RADIANCE and Targa 8-bit color-mapped
image files (type 1 in Targa's documentation). In the
default mode, a RADIANCE picture is converted to a colormapped
Targa file of the same horizontal and vertical
dimensions with 8-bits per pixel. The -d option turns off
dithering. The -b option converts the image to black and
white. Only with this option can the input be taken from
stdin. The -c option allows fewer than 256 colors. The -g
option specifies the exponent used in gamma correction; the
default value is 2.2. An exponent of 1.0 turns gamma
correction off. The -e option specifies an exposure
compensation in f-stops (powers of two). Only integer stops
are allowed, for efficiency. The -n option specifies a
sampling factor for neural network color quantization. This
value should be between 1 and 80, where 1 takes the longest
and produces the best results in small areas of the image.
If no value is given, a faster median cut algorithm is used.
The -r option invokes a reverse conversion, from an 8-bit
Targa file to a RADIANCE picture. If the output file is
missing, the standard output is used.
Greg Ward
Anthony Dekker provided the code for neural network color
quantization
Run-length encoded files can be read but not written with
this program.
pfilt(1), ra_bn(1), ra_ppm(1), ra_pr(1), ra_pr24(1),
ra_t16(1), ra_tiff(1), ximage(1)
Header and Footer
RA_T8(1) RADIANCE (5/30/95) RA_T8(1)
Page 1 (printed 7/17/96)
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