When the watermark image defined in CGExtensions is larger that the original
image, then the watermark is not applied.

In class.CGImage_Watermark_Filter.php, function "transform", I removed :
if( $image['width'] < $this->_width || $image['height'] < $this->_height ) 
      {
			return $_dest;
      }

And now it works. This is very useful when you have different images sizes, and
you want to always have something like a "credit" transparent image over the
picture.

Hope this will help