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

       pamstretch - scale up a PNM or PAM image by interpolating between pixels.



       [-yscale=Y] [-blackedge]




       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.

       This program is part of Netpbm(1).

       pamstretch  scales up pictures by integer values, either vertically, horizontally, or both.   pamstretch   dif-
       fers  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.

       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.

              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 is the vertical scale factor.  If you don't specify this, but do specify a horizontal scale factor,
              the vertical scale factor is 1.

              interpolate to black at right/bottom edges.

              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.

       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).

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

       Russell Marks (

netpbm documentation           11 November 2001      Pamstretch User Manual(0)