With a recent requirement to protect some images with a non-destructive watermark on a Pixelpost implementation I came across the following fairly simple solution. Using PHP and mod rewrite, you can easily apply a transparent png watermark to images as they are served or "on the fly". The original image remains unmodified! You can easily change the watermark at any time by replacing the watermark image with a different image file.

There is however a downside of some additional load on the server, as each image has to be created each time it is viewed. You do also lose some quality in the image (but I have found the result to be quite acceptable).

To apply this to Pixelpost do the following:

Create a watermark named watermark.png and place it in the admin/ directory along with the watermark_wrapper.php file below.

Next you will need to create a .htaccess file in the image/ directory with the following:

You can easily create a png watermark file with a transparent background using your favourite image editor. I have used the Gimp. I have found that the best watermarks are made of 2 separte text layers with a light colour (#e1e1e1) on top of a dark color (#000000) and slightly offset. This will show equally well on both light and dark images. I use "Comic Sans MS Bold" font.

Download the Pixelpost-Watermark.zip file with a sample watermark.png (and the original watermark.xcf - Gimp native file), .htaccess and watermark_wrapper.php.