Convert RGB color to the nearest color in palette (web safe color)?

Question

I want to convert a color either in RGB/Hex format to its nearest web-safe color.

Details about a websafe color can be found here: http://en.wikipedia.org/wiki/Web_safe_color

This website(http://www.colortools.net/color_make_web-safe.html) is able to do the way I want to, but I am not sure how to go about it in Python. Can anyone help me out here?

Answer 1

Despite being somewhat of a misnomer, the web safe color palette is indeed quite useful for color quantization. It's simple, fast, flexible, and ubiquitous. It also allows for RGB hex shorthand such as #369 instead of #336699. Here's a walkthrough:

1. Web safe colors are RGB triplets, with each value being one of the following six: 00, 33, 66, 99, CC, FF. So we can divide the max RGB value 255 by five (one less than the total possible values) to get a multiple value, 51.
2. Normalize the channel value by dividing by 255 (this makes it a value from 0-1 instead of 0-255).
3. Multiply by 5, and round the result to make sure it stays exact.

4. Multiply by 51 to get the final web safe value. All together, this looks something like:

   def getNearestWebSafeColor(r, g, b):
       r = int(round( ( r / 255.0 ) * 5 ) * 51)
       g = int(round( ( g / 255.0 ) * 5 ) * 51)
       b = int(round( ( b / 255.0 ) * 5 ) * 51)
       return (r, g, b)
   
   print getNearestWebSafeColor(65, 135, 211)
   

No need to go crazy comparing colors or creating huge lookup tables, as others have suggested. :-)