This is the command pnminterp that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator
PROGRAM:
NAME
pamstretch - scale up a PNM or PAM image by interpolating between pixels
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
pamstretch 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 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 between 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.
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.
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.
-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.
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