pamstretch(1)pamstretch(1)NAMEpamstretch - scale up a PNM or PAM image by interpolating
between pixels.
SYNOPSISpamstretch [-xscale=X] [-yscale=Y]
[-blackedge] [-dropedge] N [infile]
You can use the minimum unique abbreviation of the
options. You can use two hyphens instead of one. You can
separate an option name from its value with white space
instead of an equals sign.
DESCRIPTIONpamstretch scales up pictures by integer values, either
vertically, horizontally, or both. pamstretch differs
from pnmscale and pnmenlarge in that when it inserts the
additional rows and columns, instead of making the new row
or column a copy of its neighbor, pamstretch makes the new
row or column an interpolation between its neighbors. In
some images, this produces better looking output.
To scale up to non-integer pixel sizes, e.g. 2.5, try pam
stretch-gen(1) instead.
Options let you select alternative methods of dealing with
the right/bottom edges of the picture. Since the interpo
lation is done between the top-left corners of the scaled-
up pixels, it's not obvious what to do with the right/bot
tom edges. The default behaviour is to scale those up
without interpolation (more precisely, the right edge is
only interpolated vertically, and the bottom edge is only
interpolated horizontally), but there are two other possi
bilities, selected by the blackedge and dropedge options.
PARAMETERS
The N parameter is the scale factor. It is valid only if
you don't specify -xscale or -yscale. In that case, pam
stretch scales in both dimensions and by the scale factor
N.
OPTIONS
-xscale=X
This is the horizontal scale factor. If you don't
specify this, but do specify a vertical scale fac
tor, the horizontal scale factor is 1.
-yscale=Y
This is the vertical scale factor. If you don't
specify this, but do specify a horizontal scale
factor, the vertical scale factor is 1.
-blackedge
interpolate to black at right/bottom edges.
-dropedge
drop one (source) pixel at right/bottom edges. This
is arguably more logical than the default
behaviour, but it means producing output which is a
slightly odd size.
BUGS
Usually produces fairly ugly output for PBMs. For most PBM
input you'll probably want to reduce the `noise' first
using something like pnmnlfilt(1).
SEE ALSOpamstretch-gen(1), pnmenlarge(1), pnmscale(1), pnmnl
filt(1)AUTHOR
Russell Marks (russell.marks@ntlworld.com).
11 November 2001 pamstretch(1)
