NAME
    pamstretch - scale up a PNM or PAM image by interpolating between pix-
    els.

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).