pnminterp

pamstretch(1)               General Commands Manual              pamstretch(1)

NAME
       pamstretch  - scale up a PNM or PAM image by interpolating between pix-
       els

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 be-
       tween 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  pnmnl-
       filt(1).

SEE ALSO
       pamstretch-gen(1), pnmenlarge(1), pnmscale(1), pnmnlfilt(1)

AUTHOR
       Russell Marks (russell.marks@ntlworld.com).

                               11 November 2001                  pamstretch(1)