pamstretch(1)                                                 General Commands Manual                                                pamstretch(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 out-
              put 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)