Polarize

_polarize.scss

/*
 * ===========================================================================
 *
 * Polarize
 *
 * ===========================================================================
 *
 * Calculates the perceived brightness by measuring weighted distance
 * in 3D RGB space
 *
 * Based on the work from:
 * http://www.nbdtech.com/Blog/archive/2008/04/27/Calculating-the-Perceived-Brightness-of-a-Color.aspx
 *
 * http://cadik.posvete.cz/color_to_gray_evaluation/
 *
 */



/**
 * Default variables.
 */
$black:							#222 !default;
$white:							#eee !default;



/* Polarize variables
   ========================================================================== */
$polarize-black:				$black !default;
$polarize-white:				$white !default;

/* Every value in the range of 128-145 gives acceptable results */
$polarize-cutoff:				130 !default;

$polarize-red-coefficients:		241 !default;
$polarize-green-coefficients:	691 !default;
$polarize-blue-coefficients:	68 !default;

$polarize-brightness-divisor: 	$polarize-red-coefficients + $polarize-green-coefficients + $polarize-blue-coefficients;


$polarize-cutoff: round((strip-units(lightness($polarize-white)) - strip-units(lightness($polarize-black))) * ($polarize-cutoff / 200)) +0%;



@function brightness($polarize-color) {

	// Extract color components
	$polarize-red-component: red($polarize-color);
	$polarize-green-component: green($polarize-color);
	$polarize-blue-component: blue($polarize-color);

	// Calculate a brightness value in 3d color space between 0 and 255
	$number: sqrt((($polarize-red-component * $polarize-red-component * $polarize-red-coefficients) + ($polarize-green-component * $polarize-green-component * $polarize-green-coefficients) + ($polarize-blue-component * 	$polarize-blue-component * $polarize-blue-coefficients)) / $polarize-brightness-divisor);

	// Convert to percentage and return
	@return 100% * $number / 255;
}



@function contrast($polarize-color, $w: $polarize-white, $b: $polarize-black) {

	@if brightness($polarize-color) < $polarize-cutoff {

		@return $w;

	}

	@else {

		@return $b;

	}

}