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

       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  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.

       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, pamstretch 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 using 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)