Pamstretch User Manual(0)			     Pamstretch User Manual(0)



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
       This program is part of Netpbm(1).

       pamstretch  scales up pictures by integer  values,  either  vertically,
       horizontally,  or  both.	  pamstretch  differs from pamscale and pamen-
       large 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	pnmnl-
       filt(1).


SEE ALSO
       pamstretch-gen(1), pamenlarge(1), pamscale(1), pnmnlfilt(1)


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



netpbm documentation	       11 November 2001	     Pamstretch User Manual(0)