How to Convert RGB Color to HSV?

Question

How can I convert a RGB Color to HSV using C#?
I've searched for a fast method without using any external library.

Answer 1

Note that Color.GetSaturation() and Color.GetBrightness() return HSL values, not HSV.
The following code demonstrates the difference.

Color original = Color.FromArgb(50, 120, 200); // original = {Name=ff3278c8, ARGB=(255, 50, 120, 200)}  double hue; double saturation; double value; ColorToHSV(original, out hue, out saturation, out value); // hue        = 212.0 // saturation = 0.75 // value      = 0.78431372549019607  Color copy = ColorFromHSV(hue, saturation, value); // copy = {Name=ff3278c8, ARGB=(255, 50, 120, 200)}  // Compare that to the HSL values that the .NET framework provides:  original.GetHue();        // 212.0 original.GetSaturation(); // 0.6 original.GetBrightness(); // 0.490196079 

The following C# code is what you want. It converts between RGB and HSV using the algorithms described on Wikipedia. The ranges are 0 - 360 for hue, and 0 - 1 for saturation or value.

public static void ColorToHSV(Color color, out double hue, out double saturation, out double value) {     int max = Math.Max(color.R, Math.Max(color.G, color.B));     int min = Math.Min(color.R, Math.Min(color.G, color.B));      hue = color.GetHue();     saturation = (max == 0) ? 0 : 1d - (1d * min / max);     value = max / 255d; }  public static Color ColorFromHSV(double hue, double saturation, double value) {     int hi = Convert.ToInt32(Math.Floor(hue / 60)) % 6;     double f = hue / 60 - Math.Floor(hue / 60);      value = value * 255;     int v = Convert.ToInt32(value);     int p = Convert.ToInt32(value * (1 - saturation));     int q = Convert.ToInt32(value * (1 - f * saturation));     int t = Convert.ToInt32(value * (1 - (1 - f) * saturation));      if (hi == 0)         return Color.FromArgb(255, v, t, p);     else if (hi == 1)         return Color.FromArgb(255, q, v, p);     else if (hi == 2)         return Color.FromArgb(255, p, v, t);     else if (hi == 3)         return Color.FromArgb(255, p, q, v);     else if (hi == 4)         return Color.FromArgb(255, t, p, v);     else         return Color.FromArgb(255, v, p, q); } 

Answer 2

Have you considered simply using System.Drawing namespace? For example:

System.Drawing.Color color = System.Drawing.Color.FromArgb(red, green, blue); float hue = color.GetHue(); float saturation = color.GetSaturation(); float lightness = color.GetBrightness(); 

Note that it's not exactly what you've asked for (see differences between HSL and HSV and the Color class does not have a conversion back from HSL/HSV but the latter is reasonably easy to add.