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)