pnminterp - scale up portable anymap by interpolating
between pixels.
SYNOPSIS
pnminterp [-blackedge] [-dropedge] N [pnmfile]
You can use the minimum unique abbreviation of the
options.
DESCRIPTION
Pnminterp scales up pictures, producing output with one
NxN pixel for each pixel in the original image. Where
pnminterp improves over using pnmscale/pnmenlarge for this
is that it interpolates between pixels, producing better-
looking output.
To scale up to non-integer pixel sizes, e.g. 2.5, try
pnminterp-gen(1) instead.
OPTIONS
The 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, listed below.
-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).
Always produces images with a maxval of 255, which may
lose sample resolution if the input is (say) a 16-bit PGM.
SEE ALSO
pnmenlarge(1), pnmscale(1), pnmnlfilt(1)
AUTHOR
Russell Marks (russell.marks@ntlworld.com).
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