c# finding similar colors

Question

I want to call a method with argument color. But there are a lot of colors which differ only by a shade. How can I find the colors which differ from my color only by little, for example AntiqueWhite and Bisque. Here's the color palette.

Bitmap LogoImg = new Bitmap("file1.jpeg");//the extension can be some other
System.Drawing.Color x = LogoImg.GetPixel(LogoImg.Width-1, LogoImg.Height-1);
LogoImg.MakeTransparent(x);
image1.Source = GetBitmapSource(LogoImg);

possible duplicate of [finding similar colors programatically](http://stackoverflow.com/questions/1725505/finding-similar-colors-programatically) — Emond, Oct 21 '11 at 07:34
@alexn The method which gets argument color, makes that color transparent. — petko_stankoski, Oct 21 '11 at 07:39

score 16 · Answer 1 · answered Oct 21 '11 at 07:35

Could you use a method like this:

 public bool AreColorsSimilar(Color c1, Color c2, int tolerance)
 {
     return Math.Abs(c1.R - c2.R) < tolerance &&
            Math.Abs(c1.G - c2.G) < tolerance &&
            Math.Abs(c1.B - c2.B) < tolerance;
 }

This method takes two colours and a tolerance and returns whether those two colours are close or not based on their RGB values. I think that should do the trick but you may need to extend to include brightness and saturation.

Something else to consider, is doing the same thing, but in the HSV color space. — George Duckett, Oct 21 '11 at 07:36

score 7 · Accepted Answer · answered Oct 21 '11 at 07:36

I found this routine here:

Color nearest_color = Color.Empty;
foreach (object o in WebColors)
{
    // compute the Euclidean distance between the two colors
    // note, that the alpha-component is not used in this example
    dbl_test_red = Math.Pow(Convert.ToDouble(((Color)o).R) - dbl_input_red, 2.0);
    dbl_test_green = Math.Pow(Convert.ToDouble
        (((Color)o).G) - dbl_input_green, 2.0);
    dbl_test_blue = Math.Pow(Convert.ToDouble
        (((Color)o).B) - dbl_input_blue, 2.0);

    temp = Math.Sqrt(dbl_test_blue + dbl_test_green + dbl_test_red);
    // explore the result and store the nearest color
    if(temp == 0.0)
    {
        nearest_color = (Color)o;
        break;
    }
    else if (temp < distance)
    {
        distance = temp;
        nearest_color = (Color)o;
    }
}

It's a colors palette. Take a look [here](http://pietschsoft.com/post/2006/06/29/C-NET-Convert-SystemDrawingColor-to-HTML-color.aspx) to convert it to something different — Marco, Oct 21 '11 at 07:50
There's no real reason to take the square root, though. the closest value will be the closest value, even without adding that CPU-heavy operation. — Nyerguds, Apr 23 '17 at 20:44

score 4 · Answer 3 · answered Oct 21 '11 at 12:50

You can get the closest color from the KnownColors enum.

// A color very close to Rosy Brown
var color = Color.FromArgb(188, 143, 142);

var colors = Enum.GetValues(typeof (KnownColor))
                .Cast<KnownColor>()
                .Select(Color.FromKnownColor);

var closest = colors.Aggregate(Color.Black, 
                (accu, curr) =>
                ColorDiff(color, curr) < ColorDiff(color, accu) ? curr : accu);

And the support method

private int ColorDiff(Color color, Color curr)
{
    return Math.Abs(color.R - curr.R) + Math.Abs(color.G - curr.G) + Math.Abs(color.B - curr.B);
}

NielW · Answer 4 · 2013-08-01T17:52:02.847

I used Keven Holditch's answer below. But I modified it for my own purposes. This version uses exclusive-or so that only one value can be off by the tolerance and still return true. (Tolerance is also <= instead of just <.)

private bool AreColorsSimilar(Color c1, Color c2, int tolerance)
{
    return Math.Abs(c1.R - c2.R) <= tolerance ^
           Math.Abs(c1.G - c2.G) <= tolerance ^
           Math.Abs(c1.B - c2.B) <= tolerance;
}

score 2 · Answer 5 · answered Oct 21 '11 at 07:37

Analyze this example Find the Nearest Color with C#. Hope gives you an idea.

enter image description here

Color nearest_color = Color.Empty;
foreach (object o in WebColors)
{
    // compute the Euclidean distance between the two colors
    // note, that the alpha-component is not used in this example
    dbl_test_red = Math.Pow(Convert.ToDouble(((Color)o).R) - dbl_input_red, 2.0);
    dbl_test_green = Math.Pow(Convert.ToDouble
        (((Color)o).G) - dbl_input_green, 2.0);
    dbl_test_blue = Math.Pow(Convert.ToDouble
        (((Color)o).B) - dbl_input_blue, 2.0);
    // it is not necessary to compute the square root
    // it should be sufficient to use:
    // temp = dbl_test_blue + dbl_test_green + dbl_test_red;
    // if you plan to do so, the distance should be initialized by 250000.0
    temp = Math.Sqrt(dbl_test_blue + dbl_test_green + dbl_test_red);
    // explore the result and store the nearest color
    if(temp == 0.0)
    {
        // the lowest possible distance is - of course - zero
        // so I can break the loop (thanks to Willie Deutschmann)
        // here I could return the input_color itself
        // but in this example I am using a list with named colors
        // and I want to return the Name-property too
        nearest_color = (Color)o;
        break;
    }
    else if (temp < distance)
    {
        distance = temp;
        nearest_color = (Color)o;
    }
}

You've just posted the same routine taken from the same site :) — Marco, Oct 21 '11 at 07:39
As you can see in timestamp tooltip, both answers are created close times. — Soner Gönül, Oct 21 '11 at 07:47
@user966638 `WebColors = GetWebColors();` you can find in solution. — Soner Gönül, Oct 21 '11 at 07:49

score 2 · Answer 6 · edited May 23 '17 at 12:09

I think to find similar colors you should take a look at the HSL or HSB color space instead of the RGB one, cause with this it is a lot easier to find similar colors.

Within .Net you can call the GetHue(), GetSaturation() and GetBrightness() method to get these values from a given color and compare these values to find similar ones.

If you need the way back from an HSB value to a color you can also use this method.

c# finding similar colors

6 Answers6

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