Manual: pamstretch

Pamstretch User Manual(1)			   General Commands Manual			   Pamstretch User Manual(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 sepa‐
       rate 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 pamenlarge 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 interpo‐
       lation is done between the top-left corners of the scaled-up pixels, it's not obvious what to do with the  right/bot‐
       tom  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  possibili‐
       ties, 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.	However, 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,	pam‐
       stretch scales in both dimensions and by the scale factor N.

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

OPTIONS
       In  addition  to	 the  options common to all programs based on libnetpbm (most notably -quiet, see  Common Options ),
       pamstretch recognizes the following command line 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 us‐
       ing something like pnmnlfilt(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				      02 February 2019				   Pamstretch User Manual(1)