pamstretch
scale up a PNM or PAM image by interpolating between pixels
see also :
pamstretch-gen - pnmenlarge - pnmscale - pnmnlfilt
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.
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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.
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.
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.
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 also
pamstretch-gen ,
pnmenlarge , pnmscale ,
pnmnlfilt
author
Russell Marks
(russell.marks[:at:]ntlworld[:dot:]com).