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pnminterp - scale up portable anymap by interpolating between pixels.
pnminterp [-blackedge] [-dropedge] N [pnmfile]
You can use the minimum
unique abbreviation of the options.
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.
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.
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.
pnmenlarge(1)
, pnmscale(1)
, pnmnlfilt(1)
Russell Marks (russell.marks@ntlworld.com).
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