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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).

                               11 November 2001                  pamstretch(1)