less_php_contrast_port.php

<?php


use Mexitek\PHPColors\Color;

class SF_static_color
{
	public static function contrast( $color, $dark = "black", $light = "white", $threshold = 0.43 ) {
		# https://github.com/oyejorge/less.php/blob/master/lib/Less/Functions.php#L438-L475
		
		$colorLuma = self::getLuminosity( $color );
		$darkLuma = self::getLuminosity( $dark );
		$lightLuma = self::getLuminosity( $light );
		
		if ($darkLuma > $lightLuma) {
			$t = $light;
			$light = $dark;
			$dark = $t;
		}
		
		return ($colorLuma < $threshold) ? $light : $dark;
	}
	
	private static function getLuminosity( $color ) {
		# https://github.com/oyejorge/less.php/blob/master/lib/Less/Tree/Color.php#L43-L53
		
		$color = new Color( $color );
		$rgb = $color->getRgb();
		
		$r = $rgb["R"] / 255;
		$g = $rgb["G"] / 255;
		$b = $rgb["B"] / 255;
		
		$r = ($r <= 0.03928) ? $r / 12.92 : pow((($r + 0.055) / 1.055), 2.4);
		$g = ($g <= 0.03928) ? $g / 12.92 : pow((($g + 0.055) / 1.055), 2.4);
		$b = ($b <= 0.03928) ? $b / 12.92 : pow((($b + 0.055) / 1.055), 2.4);
		
		return 0.2126 * $r + 0.7152 * $g + 0.0722 * $b;
	}
}