term% cat index.txt XPAND(9.1) XPAND(9.1)
NAME
xpand, picnegate - adjust dynamic range
SYNOPSIS
fb/xpand [ -s ] [ input ] [ lo hi [ inlo inhi ] ]
fb/picnegate [ input ]
DESCRIPTION
Xpand linearly adjusts the dynamic range of the input picture (default
standard input) mapping value inlo to lo, and inhi to hi. Lo and hi
default to 0 and 255. If inlo and inhi are not specified, the lowest
and highest pixel values in the input image are used. By default,
then, xpand expands the image's dynamic range by mapping its smallest
pixel value to zero and its largest value to 255. Option -s causes all
channels of the input image to be considered together when computing
default values for inlo and inhi, thus preserving the hue of rgb pic‐
tures. Otherwise, each channel is treated separately. Option -s has
no effect if inlo and inhi are specified on the command line.
There is no requirement that lo be smaller than hi, or that inlo be
smaller than inhi, nor that any of those values be in the range 0 to
255. Output values not in the range 0 to 255 are clamped. For exam‐
ple,
xpand 0 255 255 0
inverts the pixel values of its input. For convenience, picnegate is a
script that executes this command.
SOURCE
/sys/src/fb/xpand.c
SEE ALSO
picfile(9.6)
XPAND(9.1)