Converting Color to ConsoleColor?

Question

What is the best way to convert a System.Drawing.Color to a similar System.ConsoleColor?

Answer 1

A simple and effective approach can be implemented by using the GetHue, GetBrightness and GetSaturation methods of the Color class.

public static ConsoleColor GetConsoleColor(this Color color) {
    if (color.GetSaturation() < 0.5) {
        // we have a grayish color
        switch ((int)(color.GetBrightness()*3.5)) {
        case 0:  return ConsoleColor.Black;
        case 1:  return ConsoleColor.DarkGray;
        case 2:  return ConsoleColor.Gray;
        default: return ConsoleColor.White;
        }
    }
    int hue = (int)Math.Round(color.GetHue()/60, MidpointRounding.AwayFromZero);
    if (color.GetBrightness() < 0.4) {
        // dark color
        switch (hue) {
        case 1:  return ConsoleColor.DarkYellow;
        case 2:  return ConsoleColor.DarkGreen;
        case 3:  return ConsoleColor.DarkCyan;
        case 4:  return ConsoleColor.DarkBlue;
        case 5:  return ConsoleColor.DarkMagenta;
        default: return ConsoleColor.DarkRed;
        }
    }
    // bright color
    switch (hue) {
    case 1:  return ConsoleColor.Yellow;
    case 2:  return ConsoleColor.Green;
    case 3:  return ConsoleColor.Cyan;
    case 4:  return ConsoleColor.Blue;
    case 5:  return ConsoleColor.Magenta;
    default: return ConsoleColor.Red;
    }
}

Note that the color names of the console do not match the well known colors. So if you test a color mapping scheme, you have to keep in mind that (for instance) in the well known colors, Gray is dark gray, Light Gray is gray, Green is dark green, Lime is pure green, and Olive is dark yellow.

Answer 2

Here are the console color hex values, as converted by .NET 4.5. First the program:

using System;
using System.Drawing;

class Program
{
    static void Main(string[] args)
    {
        foreach (var n in Enum.GetNames(typeof(ConsoleColor)))
            Console.WriteLine("{0,-12} #{1:X6}", n, Color.FromName(n).ToArgb() & 0xFFFFFF);
    }
}

And here's the output. As you can see, there's a problem with the reporting for DarkYellow. The full 32-bits of that one show up as zero. All the others have 0xFF for the alpha channel.

Black        #000000
DarkBlue     #00008B
DarkGreen    #006400
DarkCyan     #008B8B
DarkRed      #8B0000
DarkMagenta  #8B008B
DarkYellow   #000000   <-- see comments
Gray         #808080
DarkGray     #A9A9A9
Blue         #0000FF
Green        #008000
Cyan         #00FFFF
Red          #FF0000
Magenta      #FF00FF
Yellow       #FFFF00
White        #FFFFFF

edit: I got a little more carried away just now, so here's a converter from RGB to the nearest ConsoleColor value. Note that the dependency on System.Windows.Media is only for the demonstration harness; the actual function itself only references System.Drawing.

using System;
using System.Windows.Media;

class NearestConsoleColor
{
    static ConsoleColor ClosestConsoleColor(byte r, byte g, byte b)
    {
        ConsoleColor ret = 0;
        double rr = r, gg = g, bb = b, delta = double.MaxValue;

        foreach (ConsoleColor cc in Enum.GetValues(typeof(ConsoleColor)))
        {
            var n = Enum.GetName(typeof(ConsoleColor), cc);
            var c = System.Drawing.Color.FromName(n == "DarkYellow" ? "Orange" : n); // bug fix
            var t = Math.Pow(c.R - rr, 2.0) + Math.Pow(c.G - gg, 2.0) + Math.Pow(c.B - bb, 2.0);
            if (t == 0.0)
                return cc;
            if (t < delta)
            {
                delta = t;
                ret = cc;
            }
        }
        return ret;
    }

    static void Main()
    {
        foreach (var pi in typeof(Colors).GetProperties())
        {
            var c = (Color)ColorConverter.ConvertFromString(pi.Name);
            var cc = ClosestConsoleColor(c.R, c.G, c.B);

            Console.ForegroundColor = cc;
            Console.WriteLine("{0,-20} {1} {2}", pi.Name, c, Enum.GetName(typeof(ConsoleColor), cc));
        }
    }
}

The output (partial)...