pnminterp(1)

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)

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