Use JavaScript to Convert RGBA CSS Value to Hexadecimal

rgbaToHex.js

#!/usr/bin/env node

// Takes an rgba() CSS value and converts it to its 8 digit hexadecimal value.
//
// Usage: ./rgbaToHex.js "{YOUR_RGBA_STRING}"
//
// Example: ./rgbaToHex.js "rgba(197, 200, 198, .2)" => #C5C8C633

function trim (str) {
  return str.replace(/^\s+|\s+$/gm,'');
}

function rgbaToHex (rgba) {
  var inParts = rgba.substring(rgba.indexOf("(")).split(","),
      r = parseInt(trim(inParts[0].substring(1)), 10),
      g = parseInt(trim(inParts[1]), 10),
      b = parseInt(trim(inParts[2]), 10),
      a = parseFloat(trim(inParts[3].substring(0, inParts[3].length - 1))).toFixed(2);
  var outParts = [
    r.toString(16),
    g.toString(16),
    b.toString(16),
    Math.round(a * 255).toString(16).substring(0, 2)
  ];

  // Pad single-digit output values
  outParts.forEach(function (part, i) {
    if (part.length === 1) {
      outParts[i] = '0' + part;
    }
  })

  return ('#' + outParts.join(''));
}

if (process.argv.length >= 3) {
  console.log(rgbaToHex(process.argv[2]));
} else {
  console.log('You must supply an rgba() CSS string to convert.  Example: rgba(197, 200, 198, .2)');
  console.log('');
  console.log('Usage: ./rgbaToHex.js "{YOUR_RGBA_STRING}"');
  process.exit(1);
}

Sometimes yields 7-letter HEX values, eg. #fafa0ff.

You have to make a small change in the part of the method substring()

return ('#' + r.toString(16) + g.toString(16) + b.toString(16) + (a * 255).toString(16)).substring(0, 7);

This is incorrect for r,g,b,a values which result in a string of length 1 when toString(16) is called on them.

e.g rgba(255, 15, 255, 255) => #fffffff which should actually be #ff0fffff.

To fix this you will need to add a leading 0 to any value r,g,b or a which is length 1.

Thanks!

I have made changes to fix the comments above (I hope).

cc/ @bendaly818, @manuelQuiroz and @knutole