filter/tex/latex.php

   1 <?php // $Id$
   2     // latex.php
   3     // render TeX stuff using latex - this will not work on all platforms
   4     // or configurations. Only works on Linux and Mac with appropriate
   5     // software installed.
   6     // Much of this inspired/copied from Benjamin Zeiss' work
   7
   8     class latex {
   9
  10         var $temp_dir;
  11         var $error;
  12
  13         /**
  14          * Constructor - create temporary directories and build paths to
  15          * external 'helper' binaries.
  16          * Other platforms could/should be added
  17          */
  18         function latex() {
  19             global $CFG;
  20
  21             // construct directory structure
  22             $this->temp_dir = $CFG->dataroot . "/temp/latex";
  23             if (!file_exists("$CFG->dataroot/temp")) {
  24                 mkdir( "$CFG->dataroot/temp", $CFG->directorypermissions );
  25             }
  26             if (!file_exists( $this->temp_dir )) {
  27                 mkdir( $this->temp_dir, $CFG->directorypermissions );
  28             }
  29
  30         }
  31
  32         /**
  33          * Accessor function for support_platform field.
  34          * @return boolean value of supported_platform
  35          */
  36         function supported() {
  37             return $this->supported_platform;
  38         }
  39
  40         /**
  41          * Turn the bit of TeX into a valid latex document
  42          * @param string $forumula the TeX formula
  43          * @param int $fontsize the font size
  44          * @return string the latex document
  45          */
  46         function construct_latex_document( $formula, $fontsize=12 ) {
  47             // $fontsize don't affects to formula's size. $density can change size
  48
  49             global $CFG;
  50             $doc =  "\\documentclass[{$fontsize}pt]{article}\n";
  51             $doc .=  $CFG->filter_tex_latexpreamble;
  52             $doc .= "\\pagestyle{empty}\n";
  53             $doc .= "\\begin{document}\n";
  54 //dlnsk            $doc .= "$ {$formula} $\n";
  55             if (preg_match("/^[[:space:]]*\\\\begin\\{(gather|align|alignat|multline).?\\}/i",$formula)) {
  56                $doc .= "$formula\n";
  57             } else {
  58                $doc .= "$ {$formula} $\n";
  59             }
  60             $doc .= "\\end{document}\n";
  61             return $doc;
  62         }
  63
  64         /**
  65          * execute an external command, with optional logging
  66          * @param string $command command to execute
  67          * @param file $log valid open file handle - log info will be written to this file
  68          * @return return code from execution of command
  69          */
  70         function execute( $command, $log=null ) {
  71             $output = array();
  72             exec( $command, $output, $return_code );
  73             if ($log) {
  74                 fwrite( $log, "COMMAND: $command \n" );
  75                 $outputs = implode( "\n", $output );
  76                 fwrite( $log, "OUTPUT: $outputs \n" );
  77                 fwrite( $log, "RETURN_CODE: $return_code\n " );
  78             }
  79             return $return_code;
  80         }
  81
  82         /**
  83          * Render TeX string into gif
  84          * @param string $formula TeX formula
  85          * @param string $filename base of filename for output (no extension)
  86          * @param int $fontsize font size
  87          * @param int $density density value for .ps to .gif conversion
  88          * @param string $background background color (e.g, #FFFFFF).
  89          * @param file $log valid open file handle for optional logging (debugging only)
  90          * @return bool true if successful
  91          */
  92         function render( $formula, $filename, $fontsize=12, $density=240, $background='', $log=null ) {
  93
  94             global $CFG;
  95
  96             // quick check - will this work?
  97             if (empty($CFG->filter_tex_pathlatex)) {
  98                 return false;
  99             }
 100
 101             $doc = $this->construct_latex_document( $formula, $fontsize );
 102
 103             // construct some file paths
 104             $tex = "{$this->temp_dir}/$filename.tex";
 105             $dvi = "{$this->temp_dir}/$filename.dvi";
 106             $ps  = "{$this->temp_dir}/$filename.ps";
 107             $gif = "{$this->temp_dir}/$filename.gif";
 108
 109             // turn the latex doc into a .tex file in the temp area
 110             $fh = fopen( $tex, 'w' );
 111             fputs( $fh, $doc );
 112             fclose( $fh );
 113
 114             // run latex on document
 115             $command = "{$CFG->filter_tex_pathlatex} --interaction=nonstopmode $tex";
 116             chdir( $this->temp_dir );
 117             if ($this->execute($command, $log)) { // It allways False on Windows
 118 //                return false;
 119             }
 120
 121             // run dvips (.dvi to .ps)
 122             $command = "{$CFG->filter_tex_pathdvips} -E $dvi -o $ps";
 123             if ($this->execute($command, $log )) {
 124                 return false;
 125             }
 126
 127             // run convert on document (.ps to .gif)
 128             if ($background) {
 129                 $bg_opt = "-transparent \"$background\""; // Makes transparent background
 130             } else {
 131                 $bg_opt = "";
 132             }
 133             $command = "{$CFG->filter_tex_pathconvert} -density $density -trim $bg_opt $ps $gif";
 134             if ($this->execute($command, $log )) {
 135                 return false;
 136             }
 137
 138             return $gif;
 139         }
 140
 141         /**
 142          * Delete files created in temporary area
 143          * Don't forget to copy the final gif before calling this
 144          * @param string $filename file base (no extension)
 145          */
 146         function clean_up( $filename ) {
 147             unlink( "{$this->temp_dir}/$filename.tex" );
 148             unlink( "{$this->temp_dir}/$filename.dvi" );
 149             unlink( "{$this->temp_dir}/$filename.ps" );
 150             unlink( "{$this->temp_dir}/$filename.gif" );
 151             unlink( "{$this->temp_dir}/$filename.aux" );
 152             unlink( "{$this->temp_dir}/$filename.log" );
 153             return;
 154         }
 155
 156     }
 157
 158
 159 ?>