Color to hex and rgba converter

Simple canvas-based color converter

To answer this StackOverflow question I wrote this — a small solution based on a never-rendered <canvas> element. It fills a 1-pixel canvas with the provided fill-style, and then reads the RGBA values of that pixel. It will work with any CSS color -- name, rgba(), hex, or even something more exotic like a gradient or pattern. Invalid colors are always returned as transparent black. Transparent colors are treated as painted on a newly-cleared canvas.

It's been tested in modern-ish versions of IE, Chrome, Safari, and Firefox. The API is:

color_convert.to_hex(color)   # Converts color to a hex-based RGB triple; to_hex('red') returns '#ff0000'
color_convert.to_rgba(color)  # Converts color to an rgba() string; to_rgba('red') returns 'rgba(255,0,0,1)'

And you'll probably never want it, but you can also
color_convert.to_rgba_array(color)  # Converts color to a 4-element Uint8ClampedArray: [R, G, B, A]

Totally open-source. Call it BSD-licensed or whatever. It's a toy.

<!DOCTYPE html>
<html>
  <head>
    <title>Color to hex and rgba conversion</title>
    <script type="text/javascript" src="color-convert.js"></script>
    <script type="text/javascript">
      function update_rgba_hex() {
        var cname = document.getElementById('cname').value;
        document.getElementById('rgba').innerHTML = color_convert.to_rgba(cname);
        document.getElementById('hex').innerHTML = color_convert.to_hex(cname);
        var canvas, context;
        canvas = document.getElementById('swatch');
        context = canvas.getContext('2d');
        context.clearRect(0, 0, canvas.width, canvas.height);
        context.fillStyle = cname;
        context.fillRect(0, 0, canvas.width, canvas.height);
      }
    </script>
  </head>
  <body>
    <p>Enter a color <input size="30" id="cname" oninput="update_rgba_hex();"/> <button onclick="update_rgba_hex();">Check it</button></p>
    <p>rgba: <code id="rgba"></code></p>
    <p>hex: <code id="hex"></code></p>
    <div>
      <canvas id="swatch" width="50" height="50"></canvas>
    </div>
  </body>
</html>