so tell me
Monday, June 29, 2009 by gmc2 | Discussion: Customization Software
"premultiplied alpha".
what is it, what does it do, what does it look like without, what is it for, how do you do it???
I.R. Brainiac
Reply #2 Monday, June 29, 2009 6:19 PM
Reply #2 Monday, June 29, 2009 6:19 PM
The math for this operation is easy when the numbers are premultiplied:
- R' = RF + (1 − AF)RB
- G' = GF + (1 − AF)GB
- B' = BF + (1 − AF)BB
- A' = AF + (1 − AF)AB
The result is (0.75,0.5,0.5,0.75), which is the result of having each color's contribution to the pixel weighted by its area.
Clears thangs right up...dont it? 
DjiRate
Reply #4 Monday, June 29, 2009 7:51 PM
Reply #4 Monday, June 29, 2009 7:51 PM
The math for this operation is easy when the numbers are premultiplied:
R' = RF + (1 − AF)RB
G' = GF + (1 − AF)GB
B' = BF + (1 − AF)BB
A' = AF + (1 − AF)AB
The result is (0.75,0.5,0.5,0.75), which is the result of having each color's contribution to the pixel weighted by its area.
Clears thangs right up...dont it?
R' = RF + (1 − AF)RB
G' = GF + (1 − AF)GB
B' = BF + (1 − AF)BB
A' = AF + (1 − AF)AB
The result is (0.75,0.5,0.5,0.75), which is the result of having each color's contribution to the pixel weighted by its area.
Clears thangs right up...dont it?
well thats why they call you the Brainiac...lol...what the hell is that?
turns around and runs from this thread 
I.R. Brainiac
Reply #6 Monday, June 29, 2009 8:28 PM
Reply #6 Monday, June 29, 2009 8:28 PM
what the hell is that?
I was told there would be no math.
Thats not math Craig...its an alien language...layouts for crop circles start with that. 
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Reply #1 Monday, June 29, 2009 6:07 PM
There are a few images in SKS that need premultiplied alpha checked to look correct, Typically i use it on navigation arrow backgrounds and loggoff buttons.
To find out what it looks like with and without it.. turn it on... and off.
Not sure specifically how it works but heres some nice techy info
http://en.wikipedia.org/wiki/User:Lkesteloot/premultiplied_alpha