Ranger like function for s3, get just enough of an image to read the dimensions.

s3_ranger.php

<?php
function s3Ranger($key)
{
// inspired by https://stackoverflow.com/a/4635991/2320760 
	$s3 = new S3Client(
		array(
			'version'     => 'latest',
			'region'      => 'us-east-1',
			'credentials' => [
				'key'    => $key,
				'secret' => $secret
			]
		)
	);

	$s3->registerStreamWrapper();

	$result = $s3->headObject(
		array(
			'Bucket' => $bucket,
			'Key'    => $key,
			'Range'  => "0-65536"
		)
	);

	if (!($data = file_get_contents("s3://{$bucket}/{$key}"))) {
		throw new \Exception('Could not read file: [' . $key . ']');
	}

	$im     = imagecreatefromstring($data);
	$width  = imagesx($im);
	$height = imagesy($im);

	return [$width, $height];
}