Manualy Alpha blending two colors

[SilverWarior]

How to manualy calculate resulting color by Alphablending two existing colors?

[wagenheimer]

I have done something like this some days ago!

This link help-me a lot! http://en.wikipedia.org/wiki/Alpha_compositing


The formula I used was this one :

outRGB = srcRGB * srcAlpha + destRGB * (1-srcAlpha)

[SilverWarior]

Do you have any source code? I have seen that article and tried to implement it on my own, but I don't seem to get it working right.

Also I'm trying to implement seperate calculations for each color chanell (red, green, blue).

[User137]

That's what he meant i think. Try formula for each channel:
outR := srcR * srcAlpha + destR * (1-srcAlpha);
outG := srcG * srcAlpha + destG * (1-srcAlpha);
outB := srcB * srcAlpha + destB * (1-srcAlpha);

[LP]

Actually, the simplest (and slightly faster) alpha-blending equation is:

 Dest.R = Src1.R  + (Src2.R - Src1.R) * Alpha;
 Dest.G = Src1.G  + (Src2.G - Src1.G) * Alpha;
 Dest.B = Src1.B  + (Src2.B - Src1.B) * Alpha;

where Dest is the final color, Src1 and Src2 are the source colors with Alpha in [0..1] range.

[SilverWarior]

Thanks guys. That works like charm.