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   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          function latex() {
  19              global $CFG;
  20  
  21              // construct directory structure
  22              $this->temp_dir = $CFG->tempdir . "/latex";
  23              make_temp_directory('latex');
  24          }
  25  
  26          /**
  27           * Accessor function for support_platform field.
  28           * @return boolean value of supported_platform
  29           */
  30          function supported() {
  31              return $this->supported_platform;
  32          }
  33  
  34          /**
  35           * Turn the bit of TeX into a valid latex document
  36           * @param string $forumula the TeX formula
  37           * @param int $fontsize the font size
  38           * @return string the latex document
  39           */
  40          function construct_latex_document( $formula, $fontsize=12 ) {
  41              global $CFG;
  42  
  43              $formula = filter_tex_sanitize_formula($formula);
  44  
  45              // $fontsize don't affects to formula's size. $density can change size
  46              $doc =  "\\documentclass[{$fontsize}pt]{article}\n";
  47              $doc .= get_config('filter_tex', 'latexpreamble');
  48              $doc .= "\\pagestyle{empty}\n";
  49              $doc .= "\\begin{document}\n";
  50  //dlnsk            $doc .= "$ {$formula} $\n";
  51              if (preg_match("/^[[:space:]]*\\\\begin\\{(gather|align|alignat|multline).?\\}/i",$formula)) {
  52                 $doc .= "$formula\n";
  53              } else {
  54                 $doc .= "$ {$formula} $\n";
  55              }
  56              $doc .= "\\end{document}\n";
  57              return $doc;
  58          }
  59  
  60          /**
  61           * execute an external command, with optional logging
  62           * @param string $command command to execute
  63           * @param file $log valid open file handle - log info will be written to this file
  64           * @return return code from execution of command
  65           */
  66          function execute( $command, $log=null ) {
  67              $output = array();
  68              exec( $command, $output, $return_code );
  69              if ($log) {
  70                  fwrite( $log, "COMMAND: $command \n" );
  71                  $outputs = implode( "\n", $output );
  72                  fwrite( $log, "OUTPUT: $outputs \n" );
  73                  fwrite( $log, "RETURN_CODE: $return_code\n " );
  74              }
  75              return $return_code;
  76          }
  77  
  78          /**
  79           * Render TeX string into gif/png
  80           * @param string $formula TeX formula
  81           * @param string $filename filename for output (including extension)
  82           * @param int $fontsize font size
  83           * @param int $density density value for .ps to .gif/.png conversion
  84           * @param string $background background color (e.g, #FFFFFF).
  85           * @param file $log valid open file handle for optional logging (debugging only)
  86           * @return bool true if successful
  87           */
  88          function render( $formula, $filename, $fontsize=12, $density=240, $background='', $log=null ) {
  89  
  90              global $CFG;
  91  
  92              // quick check - will this work?
  93              $pathlatex = get_config('filter_tex', 'pathlatex');
  94              if (empty($pathlatex)) {
  95                  return false;
  96              }
  97              $pathlatex = escapeshellarg(trim($pathlatex, " '\""));
  98  
  99              $doc = $this->construct_latex_document( $formula, $fontsize );
 100  
 101              // construct some file paths
 102              $convertformat = get_config('filter_tex', 'convertformat');
 103              if (!strpos($filename, ".{$convertformat}")) {
 104                  $convertformat = 'png';
 105              }
 106              $filename = str_replace(".{$convertformat}", '', $filename);
 107              $tex = "{$this->temp_dir}/$filename.tex";
 108              $dvi = "{$this->temp_dir}/$filename.dvi";
 109              $ps  = "{$this->temp_dir}/$filename.ps";
 110              $img = "{$this->temp_dir}/$filename.{$convertformat}";
 111  
 112              // turn the latex doc into a .tex file in the temp area
 113              $fh = fopen( $tex, 'w' );
 114              fputs( $fh, $doc );
 115              fclose( $fh );
 116  
 117              // run latex on document
 118              $command = "$pathlatex --interaction=nonstopmode --halt-on-error $tex";
 119              chdir( $this->temp_dir );
 120              if ($this->execute($command, $log)) { // It allways False on Windows
 121  //                return false;
 122              }
 123  
 124              // run dvips (.dvi to .ps)
 125              $pathdvips = escapeshellarg(trim(get_config('filter_tex', 'pathdvips'), " '\""));
 126              $command = "$pathdvips -E $dvi -o $ps";
 127              if ($this->execute($command, $log )) {
 128                  return false;
 129              }
 130  
 131              // Run convert on document (.ps to .gif/.png) or run dvisvgm (.ps to .svg).
 132              if ($background) {
 133                  $bg_opt = "-transparent \"$background\""; // Makes transparent background
 134              } else {
 135                  $bg_opt = "";
 136              }
 137              if ($convertformat == 'svg') {
 138                  $pathdvisvgm = escapeshellarg(trim(get_config('filter_tex', 'pathdvisvgm'), " '\""));
 139                  $command = "$pathdvisvgm -E $ps -o $img";
 140              } else {
 141                  $pathconvert = escapeshellarg(trim(get_config('filter_tex', 'pathconvert'), " '\""));
 142                  $command = "$pathconvert -density $density -trim $bg_opt $ps $img";
 143              }
 144              if ($this->execute($command, $log )) {
 145                  return false;
 146              }
 147  
 148              return $img;
 149          }
 150  
 151          /**
 152           * Delete files created in temporary area
 153           * Don't forget to copy the final gif/png before calling this
 154           * @param string $filename file base (no extension)
 155           */
 156          function clean_up( $filename ) {
 157              global $CFG;
 158  
 159              unlink( "{$this->temp_dir}/$filename.tex" );
 160              unlink( "{$this->temp_dir}/$filename.dvi" );
 161              unlink( "{$this->temp_dir}/$filename.ps" );
 162              $convertformat = get_config('filter_tex', 'convertformat');
 163              unlink( "{$this->temp_dir}/$filename.{$convertformat}" );
 164              unlink( "{$this->temp_dir}/$filename.aux" );
 165              unlink( "{$this->temp_dir}/$filename.log" );
 166              return;
 167          }
 168  
 169      }
 170  
 171  
 172