Pamstretch User Manual(1) General Commands Manual Pamstretch User Manual(1)
NAME
pamstretch - scale up a PNM or PAM image by interpolating between pix-
els.
SYNOPSIS
pamstretch
[-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.
DESCRIPTION
This program is part of Netpbm(1).
pamstretch scales up pictures by integer values, either vertically,
horizontally, or both. pamstretch differs from pamscale and pamen-
large 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 pamstretch-gen(1)
instead.
Options let you select alternative methods of dealing with the
right/bottom edges of the picture. Since the interpolation is done be-
tween the top-left corners of the scaled-up pixels, it's not obvious
what to do with the right/bottom 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 possibilities, selected by the
-blackedge and -dropedge options.
In the special case that the stretch factor is 1, there is no issue
with the right and bottom edges, the edges of the output are identical
to the edges of the input regardless of -blackedge and -dropedge. How-
ever, before Netpbm 10.86 (March 2019), -dropedge would cause the edge
to be dropped even where the stretch factor was 1.
PARAMETERS
The N parameter is the scale factor. It is valid only if you don't
specify -xscale or -yscale. In that case, pamstretch scales in both
dimensions and by the scale factor N.
Before Netpbm 10.86 (March 2019), 1 was not a valid value.
OPTIONS
In addition to the options common to all programs based on libnetpbm
(most notably -quiet, see
Common Options ⟨index.html#commonoptions⟩ ), pamstretch recognizes the
following command line options:
-xscale=X
This is the horizontal scale factor. If you don't specify this,
but do specify a vertical scale factor, the horizontal scale
factor is 1.
This option was new in Netpbm 9.21 (December 2001).
-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.
This option was new in Netpbm 9.21 (December 2001).
-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.
LIMITATIONS
Usually produces fairly ugly output for PBMs. For most PBM input you'll
probably want to reduce the `noise' first using something like pnmnl-
filt(1).
SEE ALSO
pamstretch-gen(1), pamenlarge(1), pamscale(1), pnmnlfilt(1)
AUTHOR
Russell Marks (russell.marks@ntlworld.com).
DOCUMENT SOURCE
This manual page was generated by the Netpbm tool 'makeman' from HTML
source. The master documentation is at
http://netpbm.sourceforge.net/doc/pamstretch.html
netpbm documentation 02 February 2019 Pamstretch User Manual(1)
Generated by dwww version 1.15 on Sat Jun 29 02:28:27 CEST 2024.