How to change RGB color to HSV? In C# language. I search for very fast method without any external library.
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34Not an _exact_ duplicate. HSL != HSV. – Adam Rosenfield Dec 11 '08 at 15:01
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What to do to adapt code from HSL post to use in HSV solution? – Tomasz Smykowski Dec 11 '08 at 15:03
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7Wikipedia: Both are mathematically cylindrical, but HSV can be thought of conceptually as an inverted cone of colors, HSL conceptually represents a double-cone or sphere. While “hue” in HSL and HSV refers to the same attribute, their definitions of “saturation” differ dramatically. – BlaM Dec 11 '08 at 15:05
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2@Adam: I wish the Paint.NET people could figure that out! :) – leppie Jul 27 '09 at 10:56
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4RE-iterating: HSV is very different from HSL. HSV is sometimes known as HSB (especially in Photoshop, and in .NET) – Ian Boyd Dec 20 '09 at 15:45
6 Answers
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);
}
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i think you transposed the sample values of Saturation and Value in your answer. When i convert rgb(50,120,200) to Hue-Saturation-Value (HSV) i get hsv(212, 75%, 78.4%). Looking at wikipedia formulas for HSV: V=Max(r,g,b). In this case max(50,120,200)=200. 200/255 = 0.7843 – Ian Boyd Dec 20 '09 at 16:13
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i'll just edit the answer, transposing Saturation and Value numbers. Saturation should be 0.75, Value should be 0.7843... – Ian Boyd Dec 20 '09 at 16:16
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Any idea how to convert saturation from 0-1 to the saturation value that MS Paint uses (ie 0-240 scale)? – Jake Drew Jan 01 '16 at 02:26
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Great answer! Maybe consider using float instead of double, to be consistent with what .NET color.GetHue() returns? – user1032613 Apr 23 '16 at 23:38
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Don't know if I'm doing something wrong, but this pair of functions doesn't do round-trip for me. Doing `ToHSV(FromHSV(32,1, 1))` returns `32`, but `ToHSV(FromHSV(33,1, 1))` returns `32.9411773`. `ToHSV(FromHSV(34,1, 1))` returns `33.8823547`. `ToHSV(FromHSV(35,1, 1))` returns `35.0588264`. `ToHSV(FromHSV(36,1, 1))` returns `36` again. It appears that multiples of `4` work correctly, while others are shifted by a multiple of `1/17`. Now where does that magic number come from, I have got no idea. – dotNET Nov 28 '17 at 16:31
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1Got it. HSV variables are using `double` type, which has got much higher granularity than what 8-bit RGB channels can hold. Therefore 100% round-trip mapping is not possible. However, I'm interested in knowing if these functions can be improved to perform safely for the RGB subset. – dotNET Nov 29 '17 at 05:00
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.
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7As you point out, this doesn't actually answer the question because these methods provide a RGB to HSL conversion, not RGB to HSV. – Greg Oct 26 '09 at 17:38
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3@greg: I agree, this will lead to terrible results, as I have experienced myself. – leppie Nov 05 '09 at 12:01
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12-1: As this is not the answer to the question. HSV is very different from HSL. *Note*: HSV is sometimes known as HSB (especially in Photoshop, and in .NET) – Ian Boyd Dec 20 '09 at 15:44
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1I'm not sure what the difference is between lightness, brightness and value (always thought they were synonyms), but looking at the `System.Drawing.Color` implementation I see it is not based on the NTSC weights for Red, Green and Blue, but treat them all the same, yielding suboptimal results. – Itai Bar-Haim May 21 '13 at 15:54
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@IanBoyd While what you’re stating wrt. HSV, HSL, and HSB is correct, the problem is that the `System.Drawing` implementation of HSB appears to be, in fact, a misnomer: they’ve implemented HSL. The .NET API states that `Color.GetBrightness()` [returns lightness](https://docs.microsoft.com/en-us/dotnet/api/system.drawing.color.getbrightness), not value (i.e., it’s not the “V” in HSV, but the “L” in HSL). – Informagic Sep 07 '19 at 22:12
The EasyRGB has many color space conversions. Here is the code for the RGB->HSV conversion.
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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
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2This implementation is not correct. It seems to be [based on this example code](http://en.literateprograms.org/RGB_to_HSV_color_space_conversion_%28C%29) but it's missing a section (the normalization part). Had me tripped up for a while! – Dan Messing Aug 08 '12 at 21:25
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
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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
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This is not HSV but HSL. https://stackoverflow.com/questions/15668623/hsb-vs-hsl-vs-hsv – Sha Sep 21 '18 at 11:01