gColor Mixing
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gColor provides several Mix/Blend methods. Each take a parameter, t (Interval [0,1]), a Colour to mix and a boolean to say if the mix should be Greyscale (faster). There are also static versions which take two colours and two parameters, and a Mix method that takes an enum with the type of mix being an enum passed in. Most people just play to find out what each mode does, writing (or reading) descriptions of each method is less helpful than getting a feel from experience. Start with mixing greyscale images.
If the greyscale level is turned to an Interval in the range [0.1], multiply will keep the mix in that interval: the result will be black where either image is black.
If you expected blend to work, but ended up with white areas becoming grey, try Screen.
If t is 0 or 1 it may be wiser not to use a method here, for example, Multiply(Brush,1,Screen,0) is just going to return Brush*Screen;
Sometimes seeing what's under the hood helps a little:
Blend (Normal) :Screen* (1-t) + t*Brush Normal transparency blend.
Multiply :Screen*((1-t) + t*Brush)
Screen :1-((1-t) + t*(1-Brush)) * (1-Screen) A Blend of opposites: Negative(Blend(Negative(Brush), Negative(Screen));
Overlay :Screen<0.5 ? Screen*((1-t) + 2*t*Brush) : 1-((1-t) + 2*t*(1-Brush)) * (1-Screen)
Divide :Brush==0 ? Screen : (1-t)*Screen + t*Screen/Brush
Difference :(1-t)*Screen + t*fabs(Screen-Brush)
Subtract :Screen-=t*Brush
Add :Screen+=t*Brush
Darker :t*Brush<Screen ? t*Brush : Screen
Lighter :t*Brush>Screen ? t*Brush : Screen
Dodge :Doesn't effect dark areas. Saturates, adding 'heat'.
Burn :Doesn't effect light areas. Saturates, adding 'heat'.
Hue :Color only. Screen.Hue=Brush.Hue
Saturation :Color only. Screen.Saturation=Brush.Saturation
Color :Color only. Screen.HueAndSaturation=Brush.HueAndSaturation
Value :Color only. Screen.Value=Brush.Value
Note: The resulting colour can exceed the normal [0-1] Interval for each component (Add, really does blindly add)!


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 (1635) Last modified: Fri, 29 May 2009 19:58:17 +0100