recompress jpg files on the fly

jpeg-recompress.php

<?php

/*

pour l'installer, assurez-vous d'avoir un executable jpeg-recompress a l'emplacement indiqué,
et copier dans .htaccess les lignes suivantes

RewriteCond %{REQUEST_FILENAME} \.jpg
RewriteCond %{DOCUMENT_ROOT}/jpeg-recompress.php -f
RewriteRule \.jpg$ ./jpeg-recompress.php [QSA,L]

*/

define('_JPEG_RECOMPRESS', '/var/alternc/exec.usr/jpeg-recompress');
define('_CACHE', 'tmp/jpeg-recompress/');

$ori = '.' . preg_replace('/(\?.*|\.\.)/', '', $_SERVER['REQUEST_URI']);
$err = array();

$file = null;

if (!file_exists($ori) || !is_readable($ori)) {
  $err[] = "$ori inexistant";
@header("HTTP/1.0 404 Not Found");
#@header('Content-Type: image/jpeg');

echo join("\n",$err);
exit;
}

  $file = $ori;
  $time = filemtime($ori);
  if (!is_dir(_CACHE) and !mkdir(_CACHE) and !is_writeable(_CACHE)) {
    $err[] = "erreur cache";
    $file = $ori;
  } else if (preg_match('/raw/', $_SERVER['REQUEST_URI'])) {
    $file = $ori;
  } else {

  $md = md5($ori);
  $dir = _CACHE.substr($md,0,2).'/';
  if (!is_dir($dir)) mkdir ($dir);  
  $dest = $dir.md5($ori).'-'.basename($ori, '.jpg') . '.jpg';

  if (!file_exists($dest) or (filemtime($dest) <= $time)) {
    touch ($dest);
    $_ori = escapeshellarg($ori);
    $_dest = escapeshellarg($dest);
    $c = _JPEG_RECOMPRESS . " --accurate --quality high --no-copy $_ori $_dest";
    $a = `$c &`;
  }
  
  if (filesize($dest) > 0 ) {
    $file = $dest;
  }
}

  if ($file !== $ori) {
    $mf = @filesize($file); $mo = @filesize($ori); $ratio = sprintf("%.2d", 100*$mf/$mo);
    $log = "$file ($mf) = $ori ($mo) ; $ratio%";
    error_log($log."\n", 3, _CACHE.'jpeg-recompress.log');
  }

  @header('Content-Type: image/jpeg');
  @header('Last-Modified: '.gmdate('D, d M Y H:i:s T', $time));
  
  readfile($file);