Nearest color algorithm using Hex Triplet

Question

Wikipedia has a list of colors that I am using for a basis of color names. I want to find the nearest named color given an arbitrary RGB value.

For example #5D8AA8 hex triplet is "Air Force Blue". This information will be stored in a database table (tbl_Color (HexTriplet,ColorName)) in my system

Suppose I created a color with #5D8AA7. I need to get the nearest color available in the tbl_Color table. The expected answer is "#5D8AA8 - Air Force Blue". This is because #5D8AA8 is the nearest color for #5D8AA7.

Do we have any algorithm for finding the nearest color?

References

1. Algorithm for parsing hex into color family
2. Algorithm for finding the color between two others - in the colorspace of painted colors

Answer 1

A simple algorithm that gives reasonably good results: Add the squared difference of each color component (red, green, blue) between the color you are looking for and the color in your list of colors and choose the color where the sum of those squared differences is minimal.

For a more accurate result, see the wikipedia article on color difference and implement one of the algorithms described there.

• K.Steff: You might also want to read a little about dithering; this way the image will look more natural in a different palette. (If there is a picture, of course)
• LCJ: Do you mean the following formula - (Square(Red(source)-Red(target))) + (Square(Green(source)-Green(target))) +(Square(Blue(source)-Blue(target))) ?
• user281377: Lijo: Yes, exactly.

Answer 2

You can treat RGB colours as a 3-dimensional vector.

The distance between any two points (colors) is given by the following formula:

formula

Your color is given as: #5D8AA8

This is made up of three hexadecimal values: [5D][8A][A8]

Follow these steps:

1. Strip the # off the string
2. Break the remainder into 2x2x2 pieces and
3. Use a Hex2Dec converter to convert your color into a 3D decimal values representation

Use the formula provided above to calculate the change in color.

• user40980: This is essentially the same as the other answer (a bit better described - though more could be done). I would note that it's the difference for those RGB values. You could have a stronger answer by working through the steps to find the nearest name of the origin color (#5D8AA7) from Air Force Blue (#5D8AA8) and Carolina Blue (#56A0D3)
• Brian: Since you're only comparing magnitude, taking the square root is unnecessary. if X>Y, sqrt(X) > sqrt(Y) . See also: math.stackexchange.com/q/376730/3862
• z0mbi3: @MichaelT: great idea
• user40980: Thinking about this again (as the question got bumped) there are some additional complications to consider. Our eyes are less sensitive to blue than green. This was taken advantage of with 8 bit color giving RRRGGGBB. This can again be seen in the ppmtopgm program where it uses gray = .299 r + .587 g + .114 b. So two colors, being the same mathematical distance apart from a source, the one that is closer in green would be more similar to our eyes.
• user281377: Actually calculating the square root (as the given formula suggests) is a waste of resources. You can just as well only calculate (R²+G²+B²) and select the color with the minimal (squared) distance.