NAME
ra_t8 - convert RADIANCE picture to/from Targa 8-bit image file
SYNOPSIS
ra_t8 [ -d ][ -b ][ -c ncolors ][ -g gamma ][ -e +/-stops ][ -n sampfac
] input [ output ]
ra_t8 -r [ -g gamma ][ -e +/-stops ] [ input [ output ] ]
DESCRIPTION
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 color-mapped 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.
AUTHORS
Greg Ward
Anthony Dekker provided the code for neural network color quantization
BUGS
Run-length encoded files can be read but not written with this program.
SEE ALSO
pfilt(1), ra_bmp(1), ra_bn(1), ra_ppm(1), ra_pr(1), ra_pr24(1),
ra_t16(1), ra_tiff(1), ximage(1)