[TYPO3] GIFBUILDER with transparent background

[Xavier Perseguers]

Hello,

Does someone succeeded in creating an image (PNG) that is fully 
transparent (alpha channel) and put a text on it with any color?

I used this code

lib.banner = IMAGE
lib.banner {
	file = GIFBUILDER
	file {
		XY = [10.w],[10.h]
		format = png
		backColor = #000000
		transparentColor = #000000

		10 = TEXT
		10 {
			text = Hello World
			fontColor = #ffffff
			offset = 0,30
			fontSize = 40
		}
	}
}

But as it has no alpha channel but an indexed transparent color, I still 
see some black (in fact really dark grey) points around the letters.

-- 
Xavier Perseguers
http://xavier.perseguers.ch/en/tutorials/typo3.html