<?php    
# Written by scarfboy@gmail.com. Some modification by Stefan Parviainen.
# Use at your own risk.
# Licensed under the GPL, see gpl.txt.

#In case these are elsewhere
$path_to_latex   = '/usr/bin/latex';
$path_to_dvips   = '/usr/bin/dvips';
$path_to_convert = '/usr/bin/convert';

$imgfmt="png"; #literally used in extensions, and in parameters to convert. Should be either png or gif.


function phplatex_cleantmp($tempfname,$todir) {
  #specifically removes the various files that probably got created for a specific run, based on the run's filename.
  //global $imgfmt; // Global doesn't work for some reason
  $imgfmt="png"; #literally used in extensions, and in parameters to convert. Should be either png or gif.
  if (chdir($todir)===FALSE) { return '[directory access error, fix permissions (and empty tmp manually this time)]'; }
  error_reporting(0); #at least one of these probably will not exist, but disable the error reporting related to that.
  unlink($tempfname);     #the longer/cleaner way would be check for existance for each
  unlink($tempfname.".tex");  unlink($tempfname.".log");
  unlink($tempfname.".aux");  unlink($tempfname.".dvi");
  unlink($tempfname.".ps");   unlink($tempfname.".".$imgfmt);
  error_reporting(E_ERROR | E_WARNING | E_PARSE | E_NOTICE);
  #try-catch would have been nice. This is rather overkill too, the way I use it.
  return '';
}

function phplatex_colorhex($r,$g,$b) {
  #there has to be a better way of doing this. It's not even particularly clean.
  $hex=array("","","");
  if(strlen($hex[0]=dechex(min(256*$r,255)))==1){ $hex[0]="0".$hex[0]; }
  if(strlen($hex[1]=dechex(min(256*$g,255)))==1){ $hex[1]="0".$hex[1]; }
  if(strlen($hex[2]=dechex(min(256*$b,255)))==1){ $hex[2]="0".$hex[2]; }
  return implode("",$hex);
}


function texify($string,$dpi='90', $r=0.0,$g=0.0,$b=0.0, $br=1.0,$bg=1.0,$bb=1.0,$extraprelude="", $sharpen=FALSE) {
//global $imgfmt,$path_to_latex,$path_to_dvips,$path_to_convert;
// For some reason the globals don't work
$path_to_latex   = '/usr/bin/latex';
$path_to_dvips   = '/usr/bin/dvips';
$path_to_convert = '/usr/bin/convert';
$imgfmt="png"; #literally used in extensions, and in parameters to convert. Should be either png or gif.
  if ($dpi>300) $dpi=300;

  $back=phplatex_colorhex($br,$bg,$bb);
  $fore=phplatex_colorhex($r,$g,$b);

  # Figure out TeX, either to get the right cache entry or to, you know, compile
  # Semi-common (ams) symbol packages are included.
  $totex = "\\documentclass[14pt,landscape]{extarticle}\n".
           "\\usepackage{color}\n".
           "\\usepackage{amsmath}\n\\usepackage{amsfonts}\n\\usepackage{amssymb}\n".
           $extraprelude."\n".
           "\\pagestyle{empty}\n".  #removes header/footer; necessary for trim
           "\\begin{document}\n".
           "\\color[rgb]{".$r.",".$g.",".$b."}\n".
           "\\pagecolor[rgb]{".$br.",".$bg.",".$bb."}\n".
           $string."\n".
           "\\end{document}\n";
  
  $strhash = sha1($totex).'.'.$dpi; #file cache entry string:  40-char hash string plus size
  $stralt = str_replace("&","&amp;", preg_replace("/[\"\n]/","",$string)); #stuck in the alt and title attributes
                                                                           #May need some extra safety.
  $heredir=getcwd();

  #Experiment: Tries to adjust vertical positioning, so that rendered TeX text looks natural enough inline with HTML text
  #Only descenders are really a problem since HTML's leeway is upwards.
  #TODO: This can always use more work. 
  #      Avoid using characters that are part of TeX commands.
  #  Some things vary per font, e.g. the slash. In the default CM it is a descender, in Times and others it isn't.
  $ascenders ="/(b|d|f|h|i|j|k|l|t|A|B|C|D|E|F|G|H|I|J|L|K|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z|\[|\]|\\{|\\}|\(|\)|\/|0|1|2|3|4|5|6|7|8|9|\\#|\*|\?|'|\\\\'|\\\\`|\\\\v)/";
  $monoliners="/(a|c|e|m|n|o|r|s|u|v|w|x|z|-|=|\+|:|.)/";
  $descenders="/(g|j|p|\/|q|y|Q|,|;|\[|\]|\\{|\\}|\(|\)|\#|\\\\LaTeX|\\\\TeX|\\\\c\{)/";
  $deepdescenders="/(\[|\]|\\{|\\}|\(|\)|\\int)/";

  $ba = preg_match_all($ascenders,  $string,$m); 
  $bm = preg_match_all($monoliners, $string,$m); 
  $bd = preg_match_all($descenders, $string,$m); 
  $dd = preg_match_all($deepdescenders, $string,$m); 
  if      ($dd>0)            $verticalalign="vertical-align: -25%";   # deep descenders: move down
  else if ($bd>0 && $ba==0)  $verticalalign="vertical-align: -15%";   # descenders:  move down
  else if ($bd==0 && $ba>0)  $verticalalign="vertical-align: 0%";     # ascenders only: move up/do nothing?
  else if ($bd==0 && $ba==0) $verticalalign="vertical-align: 0%";     # neither    vertical-align: 0%
  else                       $verticalalign="vertical-align: -15%";   # both ascender and regular descender

  #check image cache, return link if exists
  #the vertical-align is to fix text baseline/descender(/tail) details in and on-average sort of way
  if (file_exists($heredir.'/images/'.$strhash.'.'.$imgfmt)) 
    return '<img style="'.$verticalalign.'" title="'.$stralt.'" alt="'.$stralt.'" src="images/'.$strhash.'.'.$imgfmt.'">';

 
  #chdir to have superfluous files be created in tmp. (you stiill have to empty this yourself)
  error_reporting(0); # not checking existence myself, that would be double.
  if (chdir("tmp")===FALSE) { return '[directory access error, fix permissions]'; } #I should chech whether file creation is allowed to give a nice error for that problem case
  error_reporting(E_ERROR | E_WARNING | E_PARSE | E_NOTICE); # TODO: set old value
  
  $tfn = tempnam(getcwd(), 'PTX'); #file in tmp dir

  #write temporary .tex file
  if ( ($tex = fopen($tfn.'.tex', "w"))==FALSE) { return '[file access error] '.phplatex_cleantmp($tfn,$heredir); }
  fwrite($tex, $totex); 
  fclose($tex);


  #Run latex to create a .dvi.  Have it try to fix minor errors instead of breaking/pausing on them.
  exec($path_to_latex.' --interaction=nonstopmode '.$tfn.'.tex');
  if (!file_exists($tfn.".dvi")) {
    $log = file_get_contents($tfn.'.log'); #The log always exists, but now it's actually interesting since it'll contain an error
    return '[latex error, code follows]<pre>'.$totex.'</pre><p><b>Log file:</b><pre>'.$log.'</pre></p> '.phplatex_cleantmp($tfn,$heredir);
  }
  

  #DVI -> PostScript.   Since dvips uses lpr, which may be configured to actually print by default, force writing to a file with -o
  exec($path_to_dvips.' '.$tfn.'.dvi -o '.$tfn.'.ps');
  if ( !file_exists($tfn.'.ps'))  {
    return '[dvi2ps error] '.phplatex_cleantmp($tfn,$heredir);
  }


  #PostScript -> image. Trim based on corner pixel, and set transparent color.
  exec($path_to_convert.' -transparent-color "#'.$back.'" -colorspace RGB -density '.$dpi.' -trim +page '.$tfn.'.ps -transparent "#'.$back.'" '.$tfn.'.'.$imgfmt);  
  #Note: +page OR -page +0+0 OR +repage moves the image to the cropped area (kills offset)
  #Older code tried: exec('/usr/bin/mogrify -density 90 -trim +page -format $imgfmt '.$tfn.'.ps');
  # It seems some versions of convert may not have -trim. Old versions?

  if (!file_exists($tfn.'.'.$imgfmt))  {
    return '[image convert error] '.phplatex_cleantmp($tfn,$heredir);
  }

  #Copy result image to chache.
  copy($tfn.'.'.$imgfmt, $heredir.'/images/'.$strhash.'.'.$imgfmt);

  #Clean up temporary files, and return link to just-created image
  return phplatex_cleantmp($tfn,$heredir).'<img style="'.$verticalalign.'" title="'.$stralt.'" alt="LaTeX formula: '.$stralt.'" src="images/'.$strhash.'.'.$imgfmt.'">';
} 
?>