NAME

       pamenlarge - Enlarge a Netpbm image N times by duplicating pixels

SYNOPSIS

       pamenlarge [-scale=integer] [-xscale=integer] [-yscale=integer] [filename]

       pamenlarge N [pnmfile]

DESCRIPTION

       This program is part of Netpbm(1).

       pamenlarge  reads  a  Netpbm image as input, replicates its pixels N times, and produces a
       Netpbm image as output.  The output is the same type of image as the input.

       If you enlarge by a factor of 3 or  more,  you  should  probably  add  a  pnmsmooth  step;
       otherwise, you can see the original pixels in the resulting image.

       For  PBM  images, pamenlarge uses special fast algorithms for scale factors up to 10.  For
       larger factors, it uses a simple but slow algorithm.  As a result, you  can  often  get  a
       significantly  faster  scale by running pamenlarge multiple times.  For example, enlarging
       by 3 and then by 5 is faster than enlarging once by 15.  And because  the  algorithms  are
       different for the different scale factors, some faster than others, the order matters too.
       For example, the following examples all produce the same  output  --  an  image  15  times
       bigger  on  edge than the input -- but at different speeds, each being faster than the one
       before.

            $ pamenlarge -scale=15 test.pbm
            $ pamenlarge -scale=5 test.pbm | pamenlarge -scale=3
            $ pamenlarge -scale=3 test.pbm | pamenlarge -scale=5

       The special fast cases for factors up to 10 have existed since Release 10.50 (March 2010).
       The  special  cases  for  1, 2, 3, and 5 go back to Release 10.41 (December 2007).  Before
       10.41, there are no special scale factors and PBM enlargement is significantly slower than
       today for all scale factors.

       pamenlarge  can enlarge only by integer factors.  The slower but more general pamscale can
       enlarge or reduce by arbitrary factors.  pamscale allows you  to  enlarge  by  resampling,
       which gives you smoother enlargements.  But it is much slower.

       pamstretch  is  another  enlarging  program  that  enlarges by integer factors.  It does a
       simple kind of resampling that gives you a smoothed enlargement  with  less  computational
       cost.

       pbmreduce can reduce by integer factors, but only for PBM images.

ARGUMENTS

       As with most Netpbm programs, you can give the input file name as an argument or omit that
       argument and have it come from Standard Input (and you can specify '-' for the argument to
       specify Standard Input explicitly).

       You  can also specify the scale factor as an argument, for backward compatibility, but the
       preferred way to do that is with a -scale option, because it is  easier  to  remember  and
       read that way.  The scale factor argument goes before the file name argument.

OPTIONS

       In addition to the options common to all programs based on libnetpbm (most notably -quiet,
       see
        Common Options ⟨index.html#commonoptions⟩ ), pamenlarge recognizes the following  command
       line options:

       -scale=integer

       -xscale=integer

       -yscale=integer
              These  specify  the  scale  factor.  -xscale specifies the horizontal scale factor;
              -yscale specifies the vertical scale factor and -scale specifies both.

              If you specify -xscale but not -yscale, pamenlarge does not scale vertically  (i.e.
              the  vertical  scale factor is 1).  The converse applies if you specify -yscale and
              not -xscale.

              You cannot specify -scale and also -xscale or yscale.

              You must specify at least one of these options,  unless  you  use  the  deprecaated
              method of specifying the scale factor via argument.

              These  options  were  all  new  in Netpbm 10.86 (March 2019).  Before that, use the
              scale argument.

HISTORY

       pamenlarge was new in Netpbm 10.25 (October 2004).  It is designed as  a  replacement  for
       pnmenlarge  by  Jef  Poskanzer,  which  was  in  Pbmplus  as  far back as 1989.  The major
       difference is that pamenlarge can enlarge PAM format images in addition to PNM.

SEE ALSO

       pbmreduce(1), pamscale(1), pamstretch(1), pbmpscale(1), pnmsmooth(1), pnm(1)

AUTHOR

       Copyright (C) 1989 by Jef Poskanzer.

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/pamenlarge.html