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         /**
  14          * Constructor - create temporary directories and build paths to
  15          * external 'helper' binaries.
  16          * Other platforms could/should be added
  17          */
  18         public function __construct() {
  19             global $CFG;
  20
  21             // construct directory structure
  22             $this->temp_dir = $CFG->tempdir . "/latex";
  23             make_temp_directory('latex');
  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             global $CFG;
  52
  53             $formula = filter_tex_sanitize_formula($formula);
  54
  55             // $fontsize don't affects to formula's size. $density can change size
  56             $doc =  "\\documentclass[{$fontsize}pt]{article}\n";
  57             $doc .= get_config('filter_tex', 'latexpreamble');
  58             $doc .= "\\pagestyle{empty}\n";
  59             $doc .= "\\begin{document}\n";
  60 //dlnsk            $doc .= "$ {$formula} $\n";
  61             if (preg_match("/^[[:space:]]*\\\\begin\\{(gather|align|alignat|multline).?\\}/i",$formula)) {
  62                $doc .= "$formula\n";
  63             } else {
  64                $doc .= "$ {$formula} $\n";
  65             }
  66             $doc .= "\\end{document}\n";
  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             $tex = "{$this->temp_dir}/$filename.tex";
 118             $dvi = "{$this->temp_dir}/$filename.dvi";
 119             $ps  = "{$this->temp_dir}/$filename.ps";
 120             $img = "{$this->temp_dir}/$filename.{$convertformat}";
 121
 122             // turn the latex doc into a .tex file in the temp area
 123             $fh = fopen( $tex, 'w' );
 124             fputs( $fh, $doc );
 125             fclose( $fh );
 126
 127             // run latex on document
 128             $command = "$pathlatex --interaction=nonstopmode --halt-on-error $tex";
 129             chdir( $this->temp_dir );
 130             if ($this->execute($command, $log)) { // It allways False on Windows
 131 //                return false;
 132             }
 133
 134             // run dvips (.dvi to .ps)
 135             $pathdvips = escapeshellarg(trim(get_config('filter_tex', 'pathdvips'), " '\""));
 136             $command = "$pathdvips -q -E $dvi -o $ps";
 137             if ($this->execute($command, $log )) {
 138                 return false;
 139             }
 140
 141             // Run convert on document (.ps to .gif/.png) or run dvisvgm (.ps to .svg).
 142             if ($background) {
 143                 $bg_opt = "-transparent \"$background\""; // Makes transparent background
 144             } else {
 145                 $bg_opt = "";
 146             }
 147             if ($convertformat == 'svg') {
 148                 $pathdvisvgm = escapeshellarg(trim(get_config('filter_tex', 'pathdvisvgm'), " '\""));
 149                 $command = "$pathdvisvgm -E $ps -o $img";
 150             } else {
 151                 $pathconvert = escapeshellarg(trim(get_config('filter_tex', 'pathconvert'), " '\""));
 152                 $command = "$pathconvert -density $density -trim $bg_opt $ps $img";
 153             }
 154             if ($this->execute($command, $log )) {
 155                 return false;
 156             }
 157
 158             return $img;
 159         }
 160
 161         /**
 162          * Delete files created in temporary area
 163          * Don't forget to copy the final gif/png before calling this
 164          * @param string $filename file base (no extension)
 165          */
 166         function clean_up( $filename ) {
 167             global $CFG;
 168
 169             unlink( "{$this->temp_dir}/$filename.tex" );
 170             unlink( "{$this->temp_dir}/$filename.dvi" );
 171             unlink( "{$this->temp_dir}/$filename.ps" );
 172             $convertformat = get_config('filter_tex', 'convertformat');
 173             unlink( "{$this->temp_dir}/$filename.{$convertformat}" );
 174             unlink( "{$this->temp_dir}/$filename.aux" );
 175             unlink( "{$this->temp_dir}/$filename.log" );
 176             return;
 177         }
 178
 179     }
 180
 181
 182