ra_t8(1) 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 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.


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.