Darken Colors

using System.Windows.Media;

public static class ColorBrightnessExtension
{
    public static Color Dark(this Color color)
    {
        return color.ChangeColorBrightness(-0.1f);
    }

    public static Color Darker(this Color color)
    {
        return color.ChangeColorBrightness(-0.5f);
    }

    public static Color Bright(this Color color)
    {
        return color.ChangeColorBrightness(+0.1f);
    }

    public static Color Brighter(this Color color)
    {
        return color.ChangeColorBrightness(+0.5f);
    }

    /// <summary>
    ///     Creates color with corrected brightness.
    /// </summary>
    /// <param name="color">Color to correct.</param>
    /// <param name="correctionFactor">
    ///     The brightness correction factor. Must be between -1 and 1.
    ///     Negative values produce darker colors.
    /// </param>
    /// <returns>
    ///     Corrected <see cref="Color" /> structure.
    ///     Source: http://www.pvladov.com/2012/09/make-color-lighter-or-darker.html
    /// </returns>
    private static Color ChangeColorBrightness(this Color color, float correctionFactor)
    {
        float red = color.R;
        float green = color.G;
        float blue = color.B;

        if (correctionFactor < 0)
        {
            correctionFactor = 1 + correctionFactor;
            red *= correctionFactor;
            green *= correctionFactor;
            blue *= correctionFactor;
        }
        else
        {
            red = (255 - red)*correctionFactor + red;
            green = (255 - green)*correctionFactor + green;
            blue = (255 - blue)*correctionFactor + blue;
        }

        return Color.FromArgb(color.A, (byte) red, (byte) green, (byte) blue);
    }
}