filter/tex/latex.php

   1 <?php
   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         /** @var bool To store value of supported_platform. */
  14         protected $supported_platform;
  15
  16         /**
  17          * Constructor - create temporary directories and build paths to
  18          * external 'helper' binaries.
  19          * Other platforms could/should be added
  20          */
  21         public function __construct() {
  22             // Construct directory structure.
  23             $this->temp_dir = make_request_directory();
  24         }
  25
  26         /**
  27          * Old syntax of class constructor. Deprecated in PHP7.
  28          *
  29          * @deprecated since Moodle 3.1
  30          */
  31         public function latex() {
  32             debugging('Use of class name as constructor is deprecated', DEBUG_DEVELOPER);
  33             self::__construct();
  34         }
  35
  36         /**
  37          * Accessor function for support_platform field.
  38          * @return boolean value of supported_platform
  39          */
  40         function supported() {
  41             return $this->supported_platform;
  42         }
  43
  44         /**
  45          * Turn the bit of TeX into a valid latex document
  46          * @param string $forumula the TeX formula
  47          * @param int $fontsize the font size
  48          * @return string the latex document
  49          */
  50         function construct_latex_document($formula, $fontsize = 12) {
  51             // $fontsize don't affects to formula's size. $density can change size
  52             $doc = "\\documentclass[{$fontsize}pt]{article}\n";
  53             $doc .= get_config('filter_tex', 'latexpreamble');
  54             $doc .= "\\pagestyle{empty}\n";
  55             $doc .= "\\begin{document}\n";
  56             if (preg_match("/^[[:space:]]*\\\\begin\\{(gather|align|alignat|multline).?\\}/i", $formula)) {
  57                $doc .= "$formula\n";
  58             } else {
  59                $doc .= "$ {$formula} $\n";
  60             }
  61             $doc .= "\\end{document}\n";
  62
  63             // Sanitize the whole document (rather than just the formula) to make sure no one can bypass sanitization
  64             // by using \newcommand in preamble to give an alias to a blocked command.
  65             $doc = filter_tex_sanitize_formula($doc);
  66
  67             return $doc;
  68         }
  69
  70         /**
  71          * execute an external command, with optional logging
  72          * @param string $command command to execute
  73          * @param file $log valid open file handle - log info will be written to this file
  74          * @return return code from execution of command
  75          */
  76         function execute($command, $log=null ) {
  77             $output = array();
  78             exec( $command, $output, $return_code );
  79             if ($log) {
  80                 fwrite( $log, "COMMAND: $command \n" );
  81                 $outputs = implode( "\n", $output );
  82                 fwrite( $log, "OUTPUT: $outputs \n" );
  83                 fwrite( $log, "RETURN_CODE: $return_code\n " );
  84             }
  85             return $return_code;
  86         }
  87
  88         /**
  89          * Render TeX string into gif/png
  90          * @param string $formula TeX formula
  91          * @param string $filename filename for output (including extension)
  92          * @param int $fontsize font size
  93          * @param int $density density value for .ps to .gif/.png conversion
  94          * @param string $background background color (e.g, #FFFFFF).
  95          * @param file $log valid open file handle for optional logging (debugging only)
  96          * @return bool true if successful
  97          */
  98         function render($formula, $filename, $fontsize=12, $density=240, $background='', $log=null ) {
  99
 100             global $CFG;
 101
 102             // quick check - will this work?
 103             $pathlatex = get_config('filter_tex', 'pathlatex');
 104             if (empty($pathlatex)) {
 105                 return false;
 106             }
 107             $pathlatex = escapeshellarg(trim($pathlatex, " '\""));
 108
 109             $doc = $this->construct_latex_document( $formula, $fontsize );
 110
 111             // construct some file paths
 112             $convertformat = get_config('filter_tex', 'convertformat');
 113             if (!strpos($filename, ".{$convertformat}")) {
 114                 $convertformat = 'png';
 115             }
 116             $filename = str_replace(".{$convertformat}", '', $filename);
 117             $tex = "$filename.tex"; // Absolute paths won't work with openin_any = p setting.
 118             $dvi = "{$this->temp_dir}/$filename.dvi";
 119             $ps  = "{$this->temp_dir}/$filename.ps";
 120             $img = "{$this->temp_dir}/$filename.{$convertformat}";
 121
 122             // Change directory to temp dir so that we can work with relative paths.
 123             chdir($this->temp_dir);
 124
 125             // turn the latex doc into a .tex file in the temp area
 126             $fh = fopen( $tex, 'w' );
 127             fputs( $fh, $doc );
 128             fclose( $fh );
 129
 130             // run latex on document
 131             $command = "$pathlatex --interaction=nonstopmode --halt-on-error $tex";
 132
 133             if ($this->execute($command, $log)) { // It allways False on Windows
 134 //                return false;
 135             }
 136
 137             // run dvips (.dvi to .ps)
 138             $pathdvips = escapeshellarg(trim(get_config('filter_tex', 'pathdvips'), " '\""));
 139             $command = "$pathdvips -q -E $dvi -o $ps";
 140             if ($this->execute($command, $log )) {
 141                 return false;
 142             }
 143
 144             // Run convert on document (.ps to .gif/.png) or run dvisvgm (.ps to .svg).
 145             if ($background) {
 146                 $bg_opt = "-transparent \"$background\""; // Makes transparent background
 147             } else {
 148                 $bg_opt = "";
 149             }
 150             if ($convertformat == 'svg') {
 151                 $pathdvisvgm = escapeshellarg(trim(get_config('filter_tex', 'pathdvisvgm'), " '\""));
 152                 $command = "$pathdvisvgm -E $ps -o $img";
 153             } else {
 154                 $pathconvert = escapeshellarg(trim(get_config('filter_tex', 'pathconvert'), " '\""));
 155                 $command = "$pathconvert -density $density -trim $bg_opt $ps $img";
 156             }
 157             if ($this->execute($command, $log )) {
 158                 return false;
 159             }
 160
 161             return $img;
 162         }
 163     }