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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 be-
       tween 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.

       In  the	special	 case  that the	stretch	factor is 1, there is no issue
       with the	right and bottom edges,	the edges of the output	are  identical
       to the edges of the input regardless of -blackedge and -dropedge.  How-
       ever, before Netpbm 10.86 (March	2019), -dropedge would cause the  edge
       to be dropped even where	the stretch factor was 1.

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.

       Before Netpbm 10.86 (March 2019), 1 was not a valid value.

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.

	      This option was new in Netpbm 9.21 (December 2001).

       -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.

	      This option was new in Netpbm 9.21 (December 2001).

       -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.

Limitations
       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).

DOCUMENT SOURCE
       This  manual  page was generated	by the Netpbm tool 'makeman' from HTML
       source.	The master documentation is at

	      http://netpbm.sourceforge.net/doc/pamstretch.html

netpbm documentation	       2 Februrary 2019	     Pamstretch	User Manual(0)

NAME | SYNOPSIS | DESCRIPTION | PARAMETERS | OPTIONS | Limitations | SEE ALSO | AUTHOR | DOCUMENT SOURCE

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