LESScss converting rgba to hex? how to nest color variables into a mixin?

Question

Does LESScss convert all rgba colors to hex values?

I am trying to create a mixin, say, .color, that allows you to pass in a color variable previously defined, and I want it to be in rgba.

this doesn't work, but here's the idea:

.bgcolor(@colorvariable,@alpha) {
     background-color: @colorvariable + rgba(0, 0, 0, @alpha);
     }

Where @colorvariable would be, @blue: rgb(17,55,76); or @green: rgb(125,188,83); etc.

I want to define a bunch of these variables, and then be able to pass them in to .bgcolor or .color mixin and change the alpha transparency on the fly.

I feel like this should be possible, but I am missing something. -Right now, my code only ever outputs a hex color value, almost no matter what I input.- If I pass in an @alpha value of 1, it outputs a hex color value. Only @alpha values less than 1 force the browser to show me an rgba value. So that's solved.

Now--how to pass in the rgb and a parts separately from a predefined variable?

Answer 1

LESS has a set of functions to fade, fadeIn, or fadeOut a color. You should be able to pass any color to these mixins (hsl, rgb, rgba, hex, etc.)

// fade color to 40%
color: fade(#000000, 40);

// fade in color by 10%
color: fadeIn(rgba(0, 0, 0, .5), 10);

// fade out color by 10%
color: fadeOut(rgba(0, 0, 0, .5), 10);

Answer 2

Turns out, less has hsla functions built in (see less color functions). So with some help, here's what we discovered:

    @dkblue: #11374c;
    .colorize_bg(@color: @white, @alpha: 1) {
           background: hsla(hue(@color), saturation(@color), lightness(@color), @alpha);}

Then use the mixin:

section {.colorize_bg(@dkblue,1);}

So we pass in the color variable @dkblue and less' functions like hue(@color) take @dkblue and pull out its hue, saturation, and lightness values. We can then pass in an alpha that we define in that mixin.

Then I can use it in other ways, like to define transparent borders. By adding background-clip: padding-box; to .colorize_bg I ensure that my borders show outside of the bg box color (isn't CSS3 magical?) Then I can redefine the mixin to work for border color:

    .colorize_border(@color: @white, @alpha: 1) {border-color: hsla(hue(@color), saturation(@color), lightness(@color), @alpha);}

and then give section the border width, style, and define color via the mixin:

section {border-width: 0 10px; border-style: solid; .colorize_border(@dkblue, .5);

And you'll get magical, shiny transparent borders, like so: https://i.stack.imgur.com/4jSKR.png

Answer 3

You don't need to convert to hsla either so you won't need a white value

.hexBackgroundToRGBA(@color,@alpha){
  @myred:red(@color);
  @mygreen:green(@color);
  @myblue:blue(@color);
  background-color: @color;
  background-color: rgba(@myred,@mygreen,@myblue,@alpha);
}

You'll have to write a few of these mixins in you need to set stuff other than the background-color property set but that's the idea. Just call it like this:

#selector{  .hexBackgroundToRGBA(@gray, 0.8); }

That will take whatever color val you have in the @gray variable and output a cross browser solution at 80% transparency with a solid color fallback for browsers that don't support rgba().