public static function hashImageOperations($imageSizes, $hashLength = 8) {
		foreach ($imageSizes as $model => $operations) {
			foreach ($operations as $name => $operation) {
				$imageSizes[$model][$name] = substr(self::operationsToString($operation, [], 'md5'), 0, $hashLength);
			}
		}
		return $imageSizes;
	}