[plugin] Watermark

/*
 *  Created: 8/2005
 *  For: MODx cms (modxcms.com)
 *  Name: Watermark
 *  Description: On the fly watermark images on your site
 *  Events: OnWebPagePrerender
 *  Version: 1.0
 *
 *  Put this text into a new plugin and set the System Event
 *  'OnWebPagePrerender'.
 *
 *  Depending on the regular expression it will take all src-
 *  fields within the <img> tag and change it.
 *  You need to install the file watermarked.php into
 *  '/assets/plugins/watermark/' for this to work.
 *
 *  You also need a '/assets/images/watermark.png' and
 *  configure the watermarked.php file to your needs.
 */

$string = $modx->documentOutput;
$pattern = "/(<img[^>]*src\s*=\s*[\'\"])([^\'^\"]*\.(jpg|jpeg))([\'\"][^>]*>)/i";
$replacement = "$1/assets/plugins/watermark/watermarked.php?src=$2$4";

$modx->documentOutput = preg_replace($pattern, $replacement, $string);

<?php  

header('content-type: image/jpeg');  

// Should be a safe image repository if you
// need to make sense.
$dirprefix = "http://sitename.com/"; 

$watermark = $dirprefix."/assets/images/watermark.png";
$image = $dirprefix.$_REQUEST['src'];

watermark($image, $watermark, 2,1);

// The minimumfactors tell how big the image must compared to the watermark
// before the watermark is applied. 2,2 means the image must be at least be 4
// times as big as the watermark.
function watermark($srcfilename, $watermark, $minumfactorx, $minumfactory) {
$imageInfo = getimagesize($srcfilename); 
$width = $imageInfo[0]; 
$height = $imageInfo[1]; 
$logoinfo = getimagesize($watermark);
$logowidth = $logoinfo[0];
$logoheight = $logoinfo[1];
$horizmargin =  $width-$logowidth;
$vertmargin =  $height-$logoheight;
$photoImage = ImageCreateFromJPEG($srcfilename);

if ($width>=($logowidth*$minumfactorx) && $height>=($logoheight*$minumfactory)) {
  // Only add watermark if watermark fits
  ImageAlphaBlending($photoImage, true);
  $logoImage = ImageCreateFromPNG($watermark);
  $logoW = ImageSX($logoImage);
  $logoH = ImageSY($logoImage);
  ImageCopy($photoImage, $logoImage, $horizmargin, $vertmargin, 0, 0, $logoW, $logoH);
}

ImageJPEG($photoImage); 
ImageDestroy($photoImage);
ImageDestroy($logoImage);
}

?>

default :
return; // stop here - this is very important.
 break;

Header ("Last-Modified: " . gmdate("D, d M Y H:i:s",mktime (0,0,0,1,1,2000)) . " GMT");  // Date in the past
Header ("Expires: Mon, 26 Jul 2040 05:00:00 GMT");    // In other words... never expire the image
Header ("Cache-Control: max-age=10000000, s-maxage=1000000, proxy-revalidate, must-revalidate");//Cache-Control header is ESSENTIAL for forcing Netscape to load all images!... and telling the ISP caches to do the same in this case cache for 1 million seconds.