## Copyright (C) 2011 Fotios Kasolis <address@hidden>
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 3 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; if not, see <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {} getpng (@var{file_name})
## @deftypefn {Function File} {} getpng (@var{file_name}, @var{res})
## Generate @code{png} file with latex formula.
##
## Given file @var{file_name} marked with @var{#f#} followed by a latex 
## formula in the form @code{$ formula $} and a newline at several places,
## @code{getpng} generates a @code{png} file with describe formula.
## Several intermediate files (@code{tex}, @code{dvi}, @code{eps}) are
## created. To use @code{genpng} you need to have ghostscript and a latex
## distribution that are accessible trough a shell as @code{gs} for linux
## platforms, @code{gswin32c} for Windows, @code{texi2dvi}, and @code{dvips}.
## The additional argument @var{res} can be used to specify the size of the
## @code{png} image in pixels (default value is 150px).
## @end deftypefn

function genpng (file_name, res)

if ( ( nargin != 1 ) && ( nargin != 2 ) )
  print_usage ();
endif

if ! ( ischar (file_name) )
  error ("genpng: expected string argument");
endif

if ( nargin == 1 )
  res = 150;
endif

m = getmarked (file_name, "#f#");

[fpath, namebody, fext, unused] = fileparts (file_name);

for i = 1:numel (m)
  fname = [namebody, num2str(i)];

  if ( exist ([ fname, ".tex" ]) )
    ans = input ([ "The file ", fname, ".tex exists. Do you want to delete it? (y/n): " ], "s");
    if ( strcmp (ans, "y") || strcmp (ans, "yes") )
      system ([ "rm ", fname, ".tex" ]);
    endif
  endif

  fid = fopen ([ fname, ".tex" ], "a+");

  fprintf (fid, "\\documentclass{article}\n\\pagestyle{empty}\n\\begin{document}\n");
  fprintf (fid, m{i});

  fprintf (fid, "\\end{document}");
  fclose (fid);

  gsexe = "gswin32c ";
 
  if ! ( ispc () )
    gsexe = "gs ";
  endif
  
  options = [ "-q -dNOPAUSE -dBATCH -sDEVICE=pngalpha -r", ...
    num2str(res), " -dEPSCrop -o ", fname, ".png ", fname, ".ps" ];

  system ([ "texi2dvi ", fname, ".tex"]);
  system ([ "dvips -E ", fname, ".dvi"]);
  system ([ gsexe, options ]);
  endfor
endfunction