color fixing code extracted from ffz

colorfix.js

// SOURCE: https://github.com/FrankerFaceZ/FrankerFaceZ/blob/master/src/colors.js

RGBAColor.prototype.luminance = function() {
	var r = bit2linear(this.r / 255),
		g = bit2linear(this.g / 255),
		b = bit2linear(this.b / 255);

	return (0.2126 * r) + (0.7152 * g) + (0.0722 * b);
}


HSLAColor.prototype.targetLuminance = function (target) {
	var s = this.s;
	s *= Math.pow(this.l > 0.5 ? -this.l : this.l - 1, 7) + 1;

	var min = 0, max = 1, d = (max - min) / 2, mid = min + d;
	for (; d > 1/65536; d /= 2, mid = min + d) {
		var luminance = RGBAColor.fromHSLA(this.h, s, mid, 1).luminance()
		if (luminance > target) {
			max = mid;
		} else {
			min = mid;
		}
	}

	return new HSLAColor(this.h, s, mid, this.a);
}

	// Setup
FFZ.settings_info.luv_contrast = { default: 4.5 /* , ... */ };

	this._hslluma_required_bright = this.settings.luv_contrast * (RGBAColor.fromCSS("#17141f").luminance() + 0.05) - 0.05;
	this._hslluma_required_dark = (RGBAColor.fromCSS("#efeef1").luminance() + 0.05) / this.settings.luv_contrast - 0.05;

	// Color Processing - HSL Luma
	if ( this.settings.fix_color === 6 ) {
		var lum = rgb.luminance();

		if ( lum > this._hslluma_required_dark )
			light_color = rgb.toHSLA().targetLuminance(this._hslluma_required_dark).toRGBA();

		if ( lum < this._hslluma_required_bright )
			dark_color = rgb.toHSLA().targetLuminance(this._hslluma_required_bright).toRGBA();
	}