TO8(1)TO8(1)NAMEto8 - Convert a 24 bit RLE file to eight bits using dithering.
SYNOPSISto8 [ -g display_gamma ] [ -{iI} image_gamma ] [ -o outfile ] [ infile
]
DESCRIPTION
To8 Converts an image with 24 bit pixel values (eight bits each of red,
green and blue) to eight bits of color using a dithered color map (the
special color map is automatically written into the output file). If
no input file is specified, to8 reads from stdin. If no output file is
specified with -o it writes the result to the standard output.
Other options allow control over the gamma, or contrast, of the image.
The dithering process assumes that the incoming image has a gamma of
1.0 (i.e., a 200 in the input represents an intensity twice that of a
100.) If this is not the case, the input values must be adjusted
before dithering via the -i or -I option. The input file may also
specify the gamma of the image via a picture comment (see below). The
output display is assumed to have a gamma of 2.5 (standard for color TV
monitors). This may be modified via the -g option if a display with a
different gamma is used.
To8 will put a picture comment into the output file indicating the dis‐
play gamma assumed in constructing the dithering color map.
OPTIONS-i image_gamma
Specify the gamma (contrast) of the image. A low contrast
image, suited for direct display without compensation on a high
contrast monitor (as most monitors are) will have a gamma of
less than one. The default image gamma is 1.0. Image gamma may
also be specified by a picture comment in the RLE (5) file of
the form image_gamma=gamma. The command line argument will
override the value in the file if specified.
-I image_gamma
An alternate method of specifying the image gamma, the number
following -I is the gamma of the display for which the image was
originally computed (and is therefore 1.0 divided by the actual
gamma of the image). Image display gamma may also be specified
by a picture comment in the RLE (5) file of the form dis‐
play_gamma=gamma. The command line argument will override the
value in the file if specified.
-g display_gamma
Specify the gamma of the X display monitor. The default value
is 2.5, suitable for most color TV monitors (this is the gamma
value assumed by the NTSC video standard).
-o outfile
If specified, the output will be written to this file. If out‐
file is "-", or if it is not specified, the output will be writ‐
ten to the standard output stream.
SEE ALSOtobw(1), getx11(1), mcut(1), rlequant(1), urt(1), dither(3), RLE(5).
AUTHOR
Spencer Thomas
4th Berkeley Distribution Month DD, YYYY TO8(1)
