Sass - Converting Hex to RGBa for background opacity - css

Question

I have the following Sass mixin, which is a half complete modification of an RGBa example:
#mixin background-opacity($color, $opacity: .3) {
background: rgb(200, 54, 54); /* The Fallback */
background: rgba(200, 54, 54, $opacity);
}
I have applied $opacity ok, but now I am a stuck with the $color part.
The colors I will be sending into the mixin will be HEX not RGB.
My example use will be:
element {
#include background-opacity(#333, .5);
}
How can I use HEX values within this mixin?

Answer 1

The rgba() function can accept a single hex color as well decimal RGB values. For example, this would work just fine:
#mixin background-opacity($color, $opacity: 0.3) {
background: $color; /* The Fallback */
background: rgba($color, $opacity);
}
element {
#include background-opacity(#333, 0.5);
}
If you ever need to break the hex color into RGB components, though, you can use the red(), green(), and blue() functions to do so:
$red: red($color);
$green: green($color);
$blue: blue($color);
background: rgb($red, $green, $blue); /* same as using "background: $color" */

Answer 2

There is a builtin mixin: transparentize($color, $amount);
background-color: transparentize(#F05353, .3);
The amount should be between 0 to 1;
Official Sass Documentation (Module: Sass::Script::Functions)

Answer 3

SASS has a built-in rgba() function.
rgba($color, $alpha)
e.g.
rgba(#00aaff, 0.5) // Output: rgba(0, 170, 255, 0.5)
An example using your own variables:
$my-color: #00aaff;
$my-opacity: 0.5;
.my-element {
color: rgba($my-color, $my-opacity);
}
// Output: .my-element {color: rgba(0, 170, 255, 0.5);}
To quote the SASS documentation:
The transparentize() function decreases the alpha channel by a
fixed amount, which is often not the desired effect.

Answer 4

you can try this solution, is the best... url(github)
// Transparent Background
// From: http://stackoverflow.com/questions/6902944/sass-mixin-for-background-transparency-back-to-ie8
// Extend this class to save bytes
.transparent-background {
background-color: transparent;
zoom: 1;
}
// The mixin
#mixin transparent($color, $alpha) {
$rgba: rgba($color, $alpha);
$ie-hex-str: ie-hex-str($rgba);
#extend .transparent-background;
background-color: $rgba;
filter:progid:DXImageTransform.Microsoft.gradient(startColorstr=#{$ie-hex-str},endColorstr=#{$ie-hex-str});
}
// Loop through opacities from 90 to 10 on an alpha scale
#mixin transparent-shades($name, $color) {
#each $alpha in 90, 80, 70, 60, 50, 40, 30, 20, 10 {
.#{$name}-#{$alpha} {
#include transparent($color, $alpha / 100);
}
}
}
// Generate semi-transparent backgrounds for the colors we want
#include transparent-shades('dark', #000000);
#include transparent-shades('light', #ffffff);

Answer 5

If you need to mix colour from variable and alpha transparency, and with solutions that include rgba() function you get an error like
background-color: rgba(#{$color}, 0.3);
^
$color: #002366 is not a color.
╷
│ background-color: rgba(#{$color}, 0.3);
│ ^^^^^^^^^^^^^^^^^^^^
Something like this might be useful.
$meeting-room-colors: (
Neumann: '#002366',
Turing: '#FF0000',
Lovelace: '#00BFFF',
Shared: '#00FF00',
Chilling: '#FF1493',
);
$color-alpha: EE;
#each $name, $color in $meeting-room-colors {
.#{$name} {
background-color: #{$color}#{$color-alpha};
}
}

Answer 6

You can use PostCSS with its postcss-rgb plugin which enables hex support in rgba() rules: arpadHegedus/postcss-rgb