How to Convert RGB Color to HSV?

tomaszs_38940 0
Viewed 119000

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

hsv rgb colors c#
7 Answers

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.

georged_703470
BlaM_9990

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
user_1064260

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;
    }
Admin1
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