Compare RGB colors in c#

What you are looking for is called Delta-E.

http://www.colorwiki.com/wiki/Delta_E:_The_Color_Difference

It is the distance between two colors in LAB color space. It is said that the human eye cannot distinguish colors below 1 DeltaE (I find that my eyes can find differences in colors below 1 DeltaE, each person is different.)

There are 4 formulas for 'color difference'.

• Delta E (CIE 1976)
• Delta E (CIE 1994)
• Delta E (CIE 2000)
• Delta E (CMC)

Check the math link on this site:

• http://www.brucelindbloom.com/

So the proper answer is to convert your RGB to LAB using the formula given, then use DeltaE 1976 to determine the 'difference' in your colors. A result of 0 would indicate identical colors. Any value higher than 0 could be judged by the rule 'A delta e of 1 or less is indistinguishable by most people'.

There's an open-source .net library that lets you do this easily: https://github.com/hvalidi/ColorMine

The most common method for comparing colors is CIE76:

var a = new Rgb { R = 149, G = 13, B = 12 }
var b = new Rgb { R = 255, G = 13, B = 12 }

var deltaE = a.Compare(b,new Cie1976Comparison());

Colors have different weights affecting human eye. So convert the colors to grayscale using their calculated weights:

Gray Color = .11 * B + .59 * G + .30 * R

And your difference will be

difference = (GrayColor1 - GrayColor2) * 100.0 / 255.0

with difference ranging from 0-100.

This is actually commonly used and very simple approach thats used calculating image differences in image procesing.

-edit this is the very simple and still usable formula - even in commercial applications. If you want to go deep you should check out the color difference methods called: CIE1976, CIE1994, CIE2000 and CMC Here you can find some more detailed info: http://en.wikipedia.org/wiki/Color_difference