sass-cmyk

Need to preprocess CMYK colors with Sass? The sass-cmyk plugin lets you construct CMYK color objects with cmyk(), adds support for performing math operations (+, *, /) on CMYK colors, and provides functions for mixing and scaling color components. sass-cmyk outputs CMYK color values using cmyk() function syntax supported by AntennaHouse and PrinceXML PDF formatters, making it a great fit for doing print typesetting with CSS.

$ gem install sass-cmyk

Or you can build from source:

$ git clone https://github.com/sandersk/sass-cmyk.git
$ cd sass-cmyk
$ gem build sass-cmyk.gemspec
$ gem install sass-cmyk-*.gem

To use the sass-cmyk plugin when running the Sass converter, just require the library using the -r option:

$ sass convert your_sass.scss -r 'sass-cmyk'

Or, if you're invoking Sass from within Ruby code, just require the sass-cmyk library:

require 'sass-cmyk'
sass_engine = Sass::Engine.for_file("your_sass.scss", :style => :compact)
results = sass_engine.render

The sass-cmyk plugin supports constructing CMYK color objects using the cmyk() function, which accepts cyan, magenta, yellow, and black values (in that order) as either floats or percents, e.g.:

$cmyk-chartreuse: cmyk(0.5, 0, 1, 0);
$cmyk-vermillion: cmyk(0%, 84%, 71%, 0%);

CMYK values can also be supplied using keyword arguments, e.g.:

$cmyk-turquoise: cmyk($cyan: 71%, $magenta: 0%, $yellow: 7%, $black: 12%);

In CSS output, CMYK color values will be output in percents. The following SCSS:

$cmyk-chartreuse: cmyk(0.5, 0,	1, 0);

h1 {
  color: $cmyk-chartreuse;
}

Will be converted to the following CSS syntax:

h1 {
  color: cmyk(50%,0%,1%,0%);
}

Which is supported by both AntennaHouse and Prince XML print typsetting applications.

To mix two CMYK colors, use either the + operator, e.g.:

$cmyk-chartreuse + $cmyk-vermillion

Or the cmyk_mix() function:

cmyk_mix($cmyk-chartreuse, $cmyk-vermillion)

When mixing colors, sass-cmyk will normalize color component values to ensure none exceed 100%, and that equivalent percentages of cyan, magenta, and yellow will be substituted with the corresponding percentage of black (i.e., if CMY values are each 30%, they can all be set to 0, and 30% can be added to K). For example, the following SCSS:

aside {
   color: cmyk(50%, 20%, 00%, 0%) + cmyk(70%, 20%, 0%, 0%);
   background-color: cmyk_mix(cmyk(30%, 50%, 0%, 0%), cmyk(10%, 0%, 30%, 0%));
}

will be converted to:

aside {
  color: cmyk(100%,40%,0%,0%);
  background-color: cmyk(10%,20%,0%,30%); 
}

To scale CMYK color values up or down proportionally by a percentage, use the cmyk_scale function, which takes a CMYK color and a percentage, e.g.:

$cmyk-salmon: cmyk(0, 0.45, 0.69, 0);
$cmyk-lighter-salmon: cmyk_scale($cmyk-salmon, 50%);

When scaling up CMYK colors, sass-cmyk will throw an error if any component value exceeds 100%, which would prevent colors from being scaled proportionally. The following will throw an error, as it would scale the yellow percentage over 100%:

cmyk_scale($cmyk-salmon, 150%)

Issues and pull requests via GitHub are welcome ☺

NB: The sass-cmyk plugin does not support conversions between CMYK and RGB color spaces. CMYK is a subtractive color model, whereas RGB is an additive model, and it is not possible to convert between the two faithfully without reference to specific ICC profiles, which is not currently within scope of this project.