Alpha Blending using comparative rgb values. [Big picture warning]

Cheers for the suggestions guys. Somewhat spookily, the combination of these two resulted in me stumbling upon the (now obvious) difference between my Mocks and my Code. Turns out that I was doing things ever so slightly differently in PSP than my code was doing on its own.

I hadn't taken into account the colorisation of the luminance for each pixel. So my transparent pixels were too pure a sample of the intended color.. Or something.. :\

Anyway, having already done this with my Image Processing Functions, it was just a code adaption. :)

tempred# = Red_Level_1#/255
tempgreen# = Green_Level_1#/255
tempblue# = Blue_Level_1#/255

greylevel# = alphalevel1#*255
If greylevel# >= 128 Then
	redlevel1# = 255 * tempred# + (1-tempred#)*(greylevel#-(255-greylevel#))
	greenlevel1# = 255 * tempgreen# + (1-tempgreen#)*(greylevel#-(255-greylevel#))
	bluelevel1# = 255 * tempblue# + (1-tempblue#)*(greylevel#-(255-greylevel#))
Else
	redlevel1# = Int(greylevel#*tempred#)*2
	greenlevel1# = Int(greylevel#*tempgreen#)*2
	bluelevel1# = Int(greylevel#*tempblue#)*2
End If

redlevel# = redlevel# - ((redlevel# - redlevel1#)*alphalevel1#)
greenlevel# = greenlevel# - ((greenlevel# - greenlevel1#)*alphalevel1#) 
bluelevel# = bluelevel# - ((bluelevel# - bluelevel1#)*alphalevel1#)

Thanks again.

Now, saying all that. It would be nice to come up with an "Additive" and "Multiplicative" version of alpha-transparency, so if anyone's got any ideas on where to begin I'd be very interested.