Image: used native PHP function for image types (#167)

Author: holantomas

src/Utils/Image.php

@@ -152,7 +152,7 @@ public static function fromFile(string $file, int &$detectedFormat = null)
 			$detectedFormat = null;
 			throw new UnknownImageFileException(is_file($file) ? "Unknown type of file '$file'." : "File '$file' not found.");
 		}
-		return new static(Callback::invokeSafe('imagecreatefrom' . self::$formats[$detectedFormat], [$file], function (string $message) {
+		return new static(Callback::invokeSafe('imagecreatefrom' . image_type_to_extension($detectedFormat, false), [$file], function (string $message) {
 			throw new ImageException($message);
 		}));
 	}
@@ -557,7 +557,7 @@ public function send(int $type = self::JPEG, int $quality = null): void
 		if (!isset(self::$formats[$type])) {
 			throw new Nette\InvalidArgumentException("Unsupported image type '$type'.");
 		}
-		header('Content-Type: image/' . self::$formats[$type]);
+		header('Content-Type: ' . image_type_to_mime_type($type));
 		$this->save(null, $quality, $type);
 	}