Untitled

/*
	Heavily modified from a bicubic resampling function by an unknown author here: http://php.net/manual/en/function.imagecopyresampled.php#78049
	this will scale down, desaturate and hash an image entirely in memory without the intermediate steps of altering the image resource and
	re-reading pixel data, and return a perceptual hash for that image. Doesn't support rotation yet and is not actually as fast as it could be
	due to the multiple looping.
*/
function fastPerceptualImageHash($res, $src_w, $src_h, $scale = 8) {
	
	$hash = array();
	
	$rX = $src_w / $scale;
	$rY = $src_h / $scale;
	$w  = 0;
	
	for ($y = 0; $y < $scale; $y++)  {
		$ow = $w; $w = round(($y + 1) * $rY);
		$t = 0;
		for ($x = 0; $x < $scale; $x++)  {
			$r = $g = $b = 0; $a = 0;
			$ot = $t; $t = round(($x + 1) * $rX);
			for ($u = 0; $u < ($w - $ow); $u++)  {
				for ($p = 0; $p < ($t - $ot); $p++)  {
					
					$rgb = imagecolorat($res, $ot + $p, $ow + $u);
					
					$r = ($rgb >> 16) & 0xFF;
					$g = ($rgb >> 8) & 0xFF;
					$b = $rgb & 0xFF;
					
					$gs = floor((($r*0.299)+($g*0.587)+($b*0.114))); 
					$hash[$x][$y] = $gs;
				}
			}
		}
	}
	
	// reset all the indexes. 
	$nhash   = array();
	$xnormal = 0;
	
	foreach($hash as $xkey => $xval) {
		foreach($hash[$xkey] as $ykey => $yval){
			unset($hash[$xkey]);
			$nhash[$xnormal][] = $yval;
		}
		$xnormal++;
	}
	
	// now hash (I really need to reduce the number of loops here.)
	$phash = array();
	
	for ($x = 0; $x < $scale; $x++) {
		
		$avg = floor(array_sum($nhash[$x]) / count(array_filter($nhash[$x])));
		
		for ($y = 0; $y < $scale; $y++) {
			$rgb = $nhash[$x][$y];
			if ($rgb > $avg) {
				$phash[] = 1;
			} else {
				$phash[] = 0;
			}
		}
	}
	return $phash;
}

function HashAsString($hash, $hex = true){
	$i = 0;
	$bucket = null;
	$return = null;
	if ($hex == true) {
		foreach($hash as $bit) {
			$i++;
			$bucket .= $bit;
			if($i == 4) {
				$return .= dechex(bindec($bucket));
				$i = 0;
				$bucket = null;
			}
		}
		return $return;
	}
	return implode(null, $hash);
}

/* test -- */

$thumb = imageCreateFromJpeg('14267384s.jpg');

list($thumb_w , $thumb_h) = getImageSize('14267384s.jpg');

$phash = HashAsString( fastPerceptualImageHash($thumb, $thumb_w , $thumb_h) );

echo $phash;

/* -- test */