pamstretch(1) - man - phpMan

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 pic‐
       ture.  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  verti‐
       cally, and the bottom edge is only interpolated horizontally), but there are two other possi‐
       bilities, 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 ver‐
              tical 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  hori‐
              zontal 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  re‐
       duce the `noise' first using something like pnmnlfilt(1).

SEE ALSO
       pamstretch-gen(1), pnmenlarge(1), pnmscale(1), pnmnlfilt(1)

AUTHOR
       Russell Marks (russell.marks AT ntlworld.com).



                                          11 November 2001                             pamstretch(1)