RGB ⇔ CMYK by C#

CmykColorConverter.cs

using System;

namespace ColorConverter
{
    class CmykColorConverter
    {
        static void Main(string[] args)
        {
            // OpenCV の色表現は BGR なので順番注意
            // 論理式としての意味合いが強いため、色の再現性は不明
            var cmyk = RgbToCmyk(12, 21, 213);// .Select(x => { Console.WriteLine(x); return x; }).ToList();
            var rgb = CmykToRgb(0.78, 0.21, 0.34, 0.24);// .Select(x => { Console.WriteLine(x); return x; }).ToList();
        }

        static double[] RgbToCmyk(byte red, byte green, byte blue)
        {
            double black = Math.Min(1.0 - red / 255.0, Math.Min(1.0 - green / 255.0, 1.0 - blue / 255.0));
            double cyan = (1.0 - (red / 255.0) - black) / (1.0 - black);
            double magenta = (1.0 - (green / 255.0) - black) / (1.0 - black);
            double yellow = (1.0 - (blue / 255.0) - black) / (1.0 - black);
            return new[] { cyan, magenta, yellow, black };
        }

        static byte[] CmykToRgb(double cyan, double magenta, double yellow, double black)
        {
            byte red = Convert.ToByte((1 - Math.Min(1, cyan * (1 - black) + black)) * 255);
            byte green = Convert.ToByte((1 - Math.Min(1, magenta * (1 - black) + black)) * 255);
            byte blue = Convert.ToByte((1 - Math.Min(1, yellow * (1 - black) + black)) * 255);
            return new[] { red, green, blue };
        }

    }
}