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.
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(1),
pnmenlarge(1),
pnmscale(1),
pnmnlfilt(1)
AUTHOR¶
Russell Marks (russell.marks@ntlworld.com).