pnminterp  -  scale  up  portable  anymap by interpolating
       between pixels.


SYNOPSIS

       pnminterp [-blackedge] [-dropedge] N [pnmfile]

       You  can  use  the  minimum  unique  abbreviation  of  the
       options.


DESCRIPTION

       Pnminterp  scales  up  pictures, producing output with one
       NxN pixel for each pixel  in  the  original  image.  Where
       pnminterp improves over using pnmscale/pnmenlarge for this
       is that it interpolates between pixels, producing  better-
       looking output.

       To  scale  up  to  non-integer  pixel sizes, e.g. 2.5, try
       pnminterp-gen(1) instead.


OPTIONS

       The 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, listed below.

       -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 pnmnlfilt(1).
       Always  produces  images  with  a maxval of 255, which may
       lose sample resolution if the input is (say) a 16-bit PGM.

SEE ALSO

       pnmenlarge(1), pnmscale(1), pnmnlfilt(1)


AUTHOR

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


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