Source

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

public static function test( $args = array() ) {
		if ( ! extension_loaded( 'gd' ) || ! function_exists( 'gd_info' ) ) {
			return false;
		}

		// On some setups GD library does not provide imagerotate() - Ticket #11536.
		if ( isset( $args['methods'] ) &&
			in_array( 'rotate', $args['methods'], true ) &&
			! function_exists( 'imagerotate' ) ) {

				return false;
		}

		return true;
	}