LESS contrast mixin - contrast mixin for LESS which works likes you'd expect it to

contrast.less

/**
 * contrast.less
 * the built-in contrast() function in LESS sucks, this one works
 * calculates the perceptual brightness of a color and assigns an int value to it
 * to determine whether contrasting color should be dark or light
 *
 * usage:
 * #contrast(@color: #f00; @threshold: 43; @dark: #222; @light: #eee; @more: '!important');
 *
 * using specific params:
 * #contrast(@threshold: 20; @light: #ccc);
 *
 * @NOTE this script assumes you have variables called:
 *  - @color-black
 *  - @color-white
 */

#contrast(@color, @property: color, @threshold: 50, @dark: @color-black, @light: @color-white-pure, @more: ~'') {
	@contrast: unit(luma(@color));

	& when (@contrast > @threshold) {
		@{property}: @dark@more;
	}

	& when not (@contrast > @threshold) {
		@{property}: @light@more;
	}
}