Programmatically choose high-contrast colors

Question

This should be a simple question, but I haven\'t been able to find a way to make it work.

Essentially, I have a silly localhost page that I use in my webdevelopment.

Answer 1

private Color GetContrastingColor(Color color)
{
    int r = color.R > 0 ? 256 - color.R : 255;
    int g = color.G > 0 ? 256 - color.G : 255;
    int b = color.B > 0 ? 256 - color.B : 255;
    return System.Drawing.Color.FromArgb(r, g, b);
}

Answer 2

Thanks to @starblue !

Here is C# code that I use

 public static string GetContrastBlackOrWhiteColorAsHtmlColorCode(Color c)
        {
            System.Drawing.Color color = System.Drawing.ColorTranslator.FromHtml("transparent");

            try
            {
                if (c.R >= 128 && c.G >= 128 && c.B >= 128)
                {
                    return System.Drawing.ColorTranslator.ToHtml(Color.Black);
                }
                else
                {
                    return System.Drawing.ColorTranslator.ToHtml(Color.White);
                }
            }
            catch (Exception)
            {
            }

            return System.Drawing.ColorTranslator.ToHtml(color);
        }

Answer 3

You can use method GetBrightness() on Color class. It returns a float value from 0.0 (brightness of black) to 1.0 (white). A simple solution would be:

var color1 = new Color.FromArgb(r1, g1, b1);
var brightness = color1.GetBrightness();

var color2 = brightness > 0.5 ? Color.Black : Color.White;

Answer 4

Check out this PHP solution: Calculating Color Contrast with PHP by Andreas Gohr. It can be ported to any language of course.

He also has a very nice demonstration of his contrast analyzer where you can find some minimal contrast levels to work with.

Answer 5

If you flip all the bits, you will get the "opposite" color which would be pretty good contrast.

I believe it's the ~ operator in C#:

R2 = ~R1;
G2 = ~G1;
B2 = ~B1;

Answer 6

These answers are more or less suggesting to use one of the two or three color choices based on whether the color is bright or dark.

I use a bit different approach and it worked elegantly in my case. Here is the implementation.

 int color = your_color;
 contrastColor = Color.rgb(255-(color >> 16)&0xFF, 255-(color >> 8)&0xFF, 255- color&0xFF);

It's simple and wonderful.