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)