deste jeito:
public static Color FromTransparentWithWhiteBG(Color A)
{
// Assuming Alpha is a value between 0 and 254...
var aFactor = (A.A/254);
var bgAFactor = (1-(A.A/254));
var background = Color.White;
var R_c = (Int32)(Math.Ceiling((Double)A.R * aFactor) + Math.Ceiling ((Double)background.R * (1 - bgAFactor )));
var G_c = (Int32)(Math.Ceiling((Double)A.G * aFactor) + Math.Ceiling ((Double)background.G * (1 - bgAFactor )));
var B_c = (Int32)(Math.Ceiling((Double)A.B * aFactor) + Math.Ceiling ((Double)background.B * (1 - bgAFactor )));
return Color.FromArgb(1, R_c, G_c, B_c);
}
fonte:http://stackoverflow.com/questions/6195609/converting-arbg-to-rgb-with-alpha-blending-with-a-white-background
att
William John Adam Trindade
Analyste-programmeur
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