.TH BBOX 9.1
.SH NAME
bbox \- compute bounding rectangle
.SH SYNOPSIS
.B fb/bbox
[
.B -s
] [
.BI -c channel
] [
.BI -v value
]
[
.I picture
]
.SH DESCRIPTION
.I Bbox
reads the given picture file (default standard input)
and prints on its standard output the minimum bounding
box of the interesting pixels of the image.
`Interesting' pixels are those for which a given channel,
specified by the
.B -c
option,
does not have a given value, specified by the
.B -v
option.
.B -v
defaults to 0, and
.B -c
defaults to the α channel (letter 'a' in the CHAN= header line)
if the image contains one, or the `m' channel otherwise.
If the image has neither α nor `m', option
.B -c
is not optional.
By default, therefore,
.I bbox
prints the bounding box of the visible parts of an image with an α
channel, or the non-black parts of a monochrome image.
.PP
Option
.B -s
causes
.I bbox
to instead copy its input to standard output, clipping the image
to the bounding rectangle.
.SH SOURCE
.B /sys/src/fb/bbox.c
.SH "SEE ALSO
.IR picfile (9.6)