Tests if color combo is AA compliant.

colorComboAA

var colorContrastUtil = (function () {

/**
 * Convert Hex value to RGB.
 * @param  {String} hex Color representation
 * @return {Object}     Object with r, g, and b, params.
 */
var hexToRgb = function (hex) {
    // Expand shorthand form (e.g. "03F") to full form (e.g. "0033FF")
    var shorthandRegex = /^#?([a-f\d])([a-f\d])([a-f\d])$/i;
    hex = hex.replace(shorthandRegex, function(m, r, g, b) {
        return r + r + g + g + b + b;
    });

    var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
    return result ? {
        r: parseInt(result[1], 16),
        g: parseInt(result[2], 16),
        b: parseInt(result[3], 16)
    } : null;
};

// from http://www.w3.org/TR/WCAG20/#relativeluminancedef
function relativeLuminanceW3C(R8bit, G8bit, B8bit) {

    var RsRGB = R8bit/255;
    var GsRGB = G8bit/255;
    var BsRGB = B8bit/255;

    var R = (RsRGB <= 0.03928) ? RsRGB/12.92 : Math.pow((RsRGB+0.055)/1.055, 2.4);
    var G = (GsRGB <= 0.03928) ? GsRGB/12.92 : Math.pow((GsRGB+0.055)/1.055, 2.4);
    var B = (BsRGB <= 0.03928) ? BsRGB/12.92 : Math.pow((BsRGB+0.055)/1.055, 2.4);

    // For the sRGB colorspace, the relative luminance of a color is defined as: 
    var L = 0.2126 * R + 0.7152 * G + 0.0722 * B;

    return L;
}

/**
 * Calculate contrast ratio by luminance.
 * @param  {Number} L1 Luminance
 * @param  {Number} L2 Luminance
 * @return {Number}    Contrast Ratio
 */
var contrastRatio = function (L1,L2) {
	var lighterLuminance = Math.max(L1, L2);
	var darkerLuminance = Math.min(L1, L2);
	return (lighterLuminance + 0.05) / (darkerLuminance + 0.05);
};

/**
 * Returns contrast ratio between two hex values.
 * @param  {String} hex1 Color representation
 * @param  {String} hex2 Color representation
 * @return {Number}      Contrast Ratio
 */
var calcContrast = function(hex1, hex2){
	var color1 = hexToRgb(hex1);
	var color2 = hexToRgb(hex2);

	var color1Luminance = relativeLuminanceW3C(color1.r, color1.g, color1.b);
	var color2Luminance = relativeLuminanceW3C(color2.r, color2.g, color2.b);

	return contrastRatio(color1Luminance, color2Luminance);
};

/**
 * Returns whether hex color combination is AA compliant.
 * @param  {String} hex1 Color representation
 * @param  {String} hex2 Color representation
 * @return {Boolean}     true if compliant
 */
var isAA = function (hex1, hex2) {
	return calcContrast(hex1, hex2) >= 4.5; // According to https://www.w3.org/TR/WCAG/#visual-audio-contrast
};

/**
 * Returns whether hex color combination is AAA compliant.
 * @param  {String} hex1 Color representation
 * @param  {String} hex2 Color representation
 * @return {Boolean}     true if compliant
 */
var isAAA = function (hex1, hex2) {
	return calcContrast(hex1, hex2) >= 7; // According to https://www.w3.org/TR/WCAG/#visual-audio-contrast
};

return {
	isAA: isAA,
	isAAA : isAAA,
	calcContrast: calcContrast
}

})();