Sass Color Helpers

2021 update: The CSS Color Module Level 5 specifies a native color-contrast() similar to ch-color-contrast().

Pure Sass, no Ruby. Should therefore be libsass compatible. Also available as a Compass extension for those who still want that.

A collection of color helpers (and some related math helpers). Handles HSL to HSV/HSB conversion, calculation of contrast (and warnings for worst case scenarios) and estimation of semi-transparent colors – everything to make it easier and more fool-proof to implement a target design and in the end get as good of a design as possible.

Lastly also some candy for the geeks: nth root and decimal exponent powers function. Because graphics can be tough.

Installation

NPM:

npm install sass-color-helpers --save

Then use something like sass-module-importer to import it.

Bower:

bower install sass-color-helpers --save

Then either manually include the individual helpers from the stylesheets/ folder or set the load path of something like grunt-contrib-sass to look for files in the bower folder – or use something like grunt-bower-install to automate it all.

Compass:

Install as a Compass extension through ruby gems: gem install sass-color-helpers

Manual:

Just copy the content of stylesheets/ into a relevant part of your project, or just pick some of the files. If you include the individual files yourself – then remember that _contrast.scss and _hsv-hsl.scss both relies on _math.scss and you should therefore include that one first.

Requirements

• Should work with all Sass 3.2 compatible preprocessors

Tested with:

• Sass Gem, v 3.3.2 – works
• node-sass (libsass), v 0.9.8 – works, excepts for the test
• sassc (libsass), v 1.0.1 – doesn't work

Helpers

Alpha Picker / Estimation

$alpha: ch-calculate-alpha(#FFF, #526D4E, #DFE4DF);
$actionColor: ch-calculate-top-color($alpha, #BEDBA1, #89D338);

Originaly published at: https://gist.github.com/voxpelli/8452877

Methods:

• ch-calculate-alpha($topColor, $bottomColor, $targetColor) – to calculate an alpha from a defined color and colors picked from a reference image
• ch-calculate-top-color($alpha, $bottomColor, $targetColor) – to calculate a color from a defined alpha and colors picked from a reference image

Contrast

$contrast: ch-color-contrast($backgroundColor, $textColor);

@if ($contrast < 3) {
  @warn "Contrast ratio of #{$textColor} on #{$backgroundColor} is pretty bad, just #{$contrast}";
}

Originally published at: https://gist.github.com/voxpelli/6304812

Based on code from: https://github.com/LeaVerou/contrast-ratio

Methods:

• ch-color-contrast($color1, $color2) – when given a background color and a front color it returns the contrast ratio between those two
• ch-best-color-contrast($base, $colors: (#fff, #000), $tolerance: 0) – when given a background color and a list of front colors it will return the first front color with the best contrast ratio. If tolerance is set to something higher than 0 than a front color later in the list will only beat a previous color if it improves the contrast ratio by at least that much – useful if one has a preferably color that one wants to use in all but the most extreme cases.

HSV/HSB to HSL

$hsv: ch-color-to-hsv($color);

$v: nth($hsv, 3);
$s: nth($hsv, 2);
$h: nth($hsv, 1);

$v: max(0%, min(100%, $v + $tweak));

$color: ch-hsv-to-color($h, $s, $v);

Originally published at: https://gist.github.com/voxpelli/1069204

Based on code from: http://ariya.blogspot.com/2008/07/converting-between-hsl-and-hsv.html

Methods:

• ch-hsv-to-hsl($h, $s: 0, $v: 0) – transforms a hsv value given by either individual parameters, or by a list as the first parameter, to a list of hsl values
• ch-hsl-to-hsv($h, $ss: 0, $ll: 0) – transforms a hsl value given by either individual parameters, a list values as the first parameter or as a color as the first parameter, to a list of hsv values
• ch-color-to-hsv($color) – alias for ch-hsl-to-hsv($color)
• ch-hsv-to-color($h, $s: 0, $v: 0) – shorthand for a ch-hsv-to-hsl($h, $s, $v) followed by a hsl() transforming the hsl values to a color
• ch-brightness($h, $s: 0, $v: 0, $adjustment: 0) – shorthand for changing the brightness of a color. If first argument is either a list of hsv values or a color then the second argument is the adjustment to apply. Otherwise the first threee arguments are the individal hsv values and the adjustment the fourth argument.

Math

Originally published at: https://gist.github.com/voxpelli/6304812

Based on code from: http://rosettacode.org/wiki/Greatest_common_divisor#JavaScript and http://rosettacode.org/wiki/Nth_root#JavaScript

Methods:

• ch-pow($base, $exponent, $prec: 12) – calculates $base raised to the power of $exponent where $exponent can be a decimal number – and if so, $prec defines the precision of the calculation
• ch-nth-root($num, $n: 2, $prec: 12) – calculates the nth root of a number with the defined precision. Used by ch-pow().
• ch-gcd($a, $b) – finds the greatest common divisor between the two values
• ch-max($v1, $v2) – returns the biggest of the two values
• ch-min($v1, $v2) – returns the smaller of the two values

License

MIT, http://voxpelli.mit-license.org

Changelog

2.0.0

• Repackaged as a Compass extension so that the code can be installed through either Compass or Bower (or manually)

1.0.0

• First packaged version of the scripts. They were previously published as gists on GitHub over a period of time.