Source

File: wp-includes/class-wp-image-editor.php

protected function make_image( $filename, $function, $arguments ) {
		$stream = wp_is_stream( $filename );
		if ( $stream ) {
			ob_start();
		} else {
			// The directory containing the original file may no longer exist when using a replication plugin.
			wp_mkdir_p( dirname( $filename ) );
		}

		$result = call_user_func_array( $function, $arguments );

		if ( $result && $stream ) {
			$contents = ob_get_contents();

			$fp = fopen( $filename, 'w' );

			if ( ! $fp ) {
				ob_end_clean();
				return false;
			}

			fwrite( $fp, $contents );
			fclose( $fp );
		}

		if ( $stream ) {
			ob_end_clean();
		}

		return $result;
	}