TalkPHP - watermark images

hi there,
I am busy with this uploading script for weeks now almost finished but now, I've stumbled upon a really annoying problem and can't figure it out.

When i try to watermark with the image below I'm getting this choppy white blocks around my images. tried GIF and PNG8bits still the same, then i tried PNG24bits converting to 8bits with pngquant :/ same again.

then I tried to make the sharp green background transparent

PHP Code:


		
			
<?php

$color = hexdec("00ff00");

imagecolortransparent($this->_watermark, $color);

?>

but that didn't work well for me

I came across iMagick from imageMagick from help of another site but i would prefer not to use extensions for PHP

I am gonna get mad because this is first time I am using PHP with file handling and don't experience verry well so if someone could help would apreciate it alot.

has anyone suggestions??