|It's the randomizing of the pixels that does it, just go to line 162 or thereabouts, and comment out the if line that is doing that, and set randomizer to 0:|
#if ($stampAverage>10) $randomizer=rand(-transparentWatermarkRandPixelLightLevel, +transparentWatermarkRandPixelLightLevel);
$randomizer = 0;
That should fix it. Then use a PNG-24 or PNG-8 set to transparent, and set the layer to 20-50% opacity.