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.

Answer 3

The EasyRGB has many color space conversions. Here is the code for the RGB->HSV conversion.

Answer 4

There's a C implementation here:

http://www.cs.rit.edu/~ncs/color/t_convert.html

Should be very straightforward to convert to C#, as almost no functions are called - just calculations.

found via Google

Answer 5

This is the VB.net version which works fine for me ported from the C code in BlaM's post.

There's a C implementation here:

http://www.cs.rit.edu/~ncs/color/t_convert.html

Should be very straightforward to convert to C#, as almost no functions are called - just > calculations.

---

Public Sub HSVtoRGB(ByRef r As Double, ByRef g As Double, ByRef b As Double, ByVal h As Double, ByVal s As Double, ByVal v As Double)
    Dim i As Integer
    Dim f, p, q, t As Double

    If (s = 0) Then
        ' achromatic (grey)
        r = v
        g = v
        b = v
        Exit Sub
    End If

    h /= 60 'sector 0 to 5
    i = Math.Floor(h)
    f = h - i 'factorial part of h
    p = v * (1 - s)
    q = v * (1 - s * f)
    t = v * (1 - s * (1 - f))

    Select Case (i)
        Case 0
            r = v
            g = t
            b = p
            Exit Select
        Case 1
            r = q
            g = v
            b = p
            Exit Select
        Case 2
            r = p
            g = v
            b = t
            Exit Select
        Case 3
            r = p
            g = q
            b = v
            Exit Select
        Case 4
            r = t
            g = p
            b = v
            Exit Select
        Case Else   'case 5:
            r = v
            g = p
            b = q
            Exit Select
    End Select
End Sub

Answer 6

I've ended up here by having the same need.

Bellow I'm sharing the best and simpler solution I could find so far.
This is a modified answer from Greg's (found here); but with a humbler and understandable code.

For those who are learning I've added a few references that are worth checking for the sake of understanding.

---

References

1. "Lukas Stratmann" HSV Model Tool (Incl. Other Model Systems: CMY / CMYK / HSL)
2. "The HSV Color Model in Graphic Design"
3. "Formula to Determine Perceived Brightness of RGB Color"
4. Fastest Formula to Get Hue from RGB
5. "Color Conversion Algorithms"
6. "Program to Change RGB color model to HSV color model"
7. "RGB to HSV Color Conversion Algorithm"
8. "RGB to HSV Color Space Conversion (C)"
9. "How to Convert RGB Color to HSV"

---

Code

    /// <summary> Convert RGB Color to HSV. </summary>
    /// <param name="color"></param>
    /// <returns> A double[] Containing HSV Color Values. </returns>
    public double[] rgbToHSV(Color color)
    {
        double[] output = new double[3];

        double hue, saturation, 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;

        output[0] = hue;
        output[1] = saturation;
        output[2] = value;

        return output;
    }

Answer 7

FIRST: make sure you have a color as a bitmap, like this:

Bitmap bmp = (Bitmap)pictureBox1.Image.Clone();
paintcolor = bmp.GetPixel(e.X, e.Y);

(e is from the event handler wich picked my color!)

What I did when I had this problem a whilke ago, I first got the rgba (red, green, blue and alpha) values. Next I created 3 floats: float hue, float saturation, float brightness. Then you simply do:

hue = yourcolor.Gethue;
saturation = yourcolor.GetSaturation;
brightness = yourcolor.GetBrightness;

The whole lot looks like this:

Bitmap bmp = (Bitmap)pictureBox1.Image.Clone();
            paintcolor = bmp.GetPixel(e.X, e.Y);
            float hue;
            float saturation;
            float brightness;
            hue = paintcolor.GetHue();
            saturation = paintcolor.GetSaturation();
            brightness = paintcolor.GetBrightness();

If you now want to display them in a label, just do:

yourlabelname.Text = hue.ToString;
yourlabelname.Text = saturation.ToString;
yourlabelname.Text = brightness.ToString;

Here you go, you now have RGB Values into HSV values :)

Hope this helps