pamstretch



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 pnmen-
       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 dont
       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), pnmenlarge(1), pamscale(1), pnmnlfilt(1)



AUTHOR

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



netpbm documentation           11 November 2001      Pamstretch User Manual(0)

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