.NET: Alpha Compositing Algorithm

Choose Background Color

First, choose a background color to be used for the transparent pixels.

Apply Alpha Compositing Algorithm

The formula for alpha compositing a single pixel typically involves blending each of the RGB values of the foreground image with those of the background color based on the alpha value. The alpha value ranges from 0 (completely transparent) to 255 (completely opaque). If the alpha value ranges from 0 to 1, simply multiply it by 255.

Here it is in C# code:

float ConvertAlphaChannelToBackground(float desiredBackgroundColor, float foregroundColor, float alpha)
{
	return (foregroundColor * alpha / 255) + (desiredBackgroundColor * (255 - alpha) / 255);
}

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