Paint.Net plugin that makes all completely transparent pixels have the same RGB values.

MonochromaticAlpha.cs

// Name: Monochromatic Alpha
// Submenu:
// Author: Banane9
// Title: Monochromatic Alpha
// Version: 1.0.0
// Desc: Makes all completely transparent pixels have the same RGB values.
// Keywords: adjustment, alpha channel, monochromatic, color, correction, fix
// URL: http://github.com/Banane9
// Help:

void Render(Surface dst, Surface src, Rectangle rect)
{
    ColorBgra primaryColor = (ColorBgra)EnvironmentParameters.PrimaryColor;

    ColorBgra currentPixel;
    for (int y = rect.Top; y < rect.Bottom; ++y)
    {
        if (IsCancelRequested)
            return;
            
        for (int x = rect.Left; x < rect.Right; ++x)
        {
            currentPixel = src[x,y];
            
            if (currentPixel.A == 0)
            {
                currentPixel.R = primaryColor.R;
                currentPixel.G = primaryColor.G;
                currentPixel.B = primaryColor.B;
            }
            
            dst[x,y] = currentPixel;
        }
    }
}