img_compare.php

static function detect($path1, $path2, $colorPrecision = null, $gaussianBlur = false)
	{
		$img1 = imagecreatefrompng($path1);
		$img2 = imagecreatefrompng($path2);

		$w1 = imagesx($img1);	$h1 = imagesy($img1);
		$w2 = imagesx($img2);	$h2 = imagesy($img2);

		# Stop early if the size of images such that images can not be part of each other
		if (($w1 > $w2 && $h2 > $h1))
			return 0;
		if ($w2 > $w1 && $h1 > $h2)
			return 0;

		if ($gaussianBlur)
		{
			imagefilter($img1, IMG_FILTER_GAUSSIAN_BLUR);
			imagefilter($img2, IMG_FILTER_GAUSSIAN_BLUR);
		}

		# Find which image can be part of which image
		if ($w1 > $w2 || $h1 > $h2
			|| ($w1 == $w2 && $h1 >= $h2)
			|| ($h1 == $h2 && $w1 >= $w2))
		{
			$full = $img1; $wf = $w1; $hf = $h1;
			$part = $img2; $wp = $w2; $hp = $h2;
			$potentialResult = 1;
		}
		else
		{
			$full = $img2; $wf = $w2; $hf = $h2;
			$part = $img1; $wp = $w1; $hp = $h1;
			$potentialResult = -1;
		}

		$rgbFull = $rgbPart = array();

		$maxX = $wf-$wp;
		$maxY = $hf-$hp;
		# $left, $top - coordinate on the full image where we place the part image
		for($left = 0; $left <= $maxX; $left++)
			for($top = 0; $top <= $maxY; $top++)
			{
				# Loop over part image
				$imageFailed = false;
				for ($xi = 0; $xi < $wp; $xi++)
				{
					for ($yi = 0; $yi < $hp; $yi++)
					{
						if (!self::sameColors($full, $left+$xi, $top+$yi, $part, $xi, $yi, $colorPrecision))
						{
							$imageFailed = true;
							break;
						}
					}
					if ($imageFailed)
						break;
				}
				if (!$imageFailed)
				{
					imagedestroy($img1);
					imagedestroy($img2);
					return $potentialResult;
				}
			}

		imagedestroy($img1);
		imagedestroy($img2);

		return 0;
	}