Convert rgba colour definition string in LESS to c

Suppose I've parsed my mixin parameters and colours are provided using rgba function.

Now I would like to mix two of those colours, but LESS mix function requires parameter instances of type color.

What I tried

...and doesn't work

calling color("rgba(0,0,0,.5)")
mix(@first, ~"@{second}") where @second is a string like rgba(0,0,0,0.5)

How do I convert to color?

I'm afraid you won't find a built in function to do this in LESS.

The color() functions argument needs to be a hexadecimal or its shorthand representation.

But you can further parse the string with javascript to

extract the individual r,g,b and alpha values,
pass the individual values to the rgba() function to get a variable of type color.

You could do the first step in your original parsing. If you need to do all in LESS you can do something like this:

  @color1: "rgba(255, 255, 0, 0.5)";
  @color2: ~`@{color1}.replace(/^(rgb|rgba)\(/,'[').replace(/\)$/,']').replace(/\s/g,'')`;
  @color3: rgba(unit(`@{color2}[0]`),unit(`@{color2}[1]`),unit(`@{color2}[2]`),unit(`@{color2}[3]`));

Unfortunately the string can not be directly read into the rgba() or similar functions as they expect multiple arguments. Even with string escaping (eg. ~) the output gets formated as a single variable (~"a, b, c" becomes a, b, c and acts as a single output string for the css), so we need to get each value individually and pass it to its respective argument/variable of the rgba() function. Using the function unit() we transform a string to a number that can be used further.

For example:

  @color4: mix(red,@color3);
  .test {
      color: @color4;
  }

resulting in CSS:

  .test{
    color: rgba(255, 64, 0, 0.75);
  }