Resources/Mpdf/Image/ImageTypeGuesser.php

<?php

namespace Mpdf\Image;

class ImageTypeGuesser
{

	/**
	 * @param string $data
	 *
	 * @return null|string
	 */
	public function guess($data)
	{
		if (in_array(substr($data, 6, 4), ['JFIF', 'Exif'], true) || strpos($data, chr(255) . chr(216)) === 0) { // 0xFF 0xD8	// mpDF 5.7.2
			return 'jpeg';
		}

		if (in_array(substr($data, 0, 6), ['GIF87a', 'GIF89a'], true)) {
			return 'gif';
		}

		if (strpos($data, chr(137) . 'PNG' . chr(13) . chr(10) . chr(26) . chr(10)) === 0) {
			return 'png';
		}

		if (strpos($data, chr(215) . chr(205) . chr(198) . chr(154)) === 0) {
			return 'wmf';
		}

		if (preg_match('/<svg.*<\/svg>/is', $data)) {
			return 'svg';
		}

		if (strpos($data, 'BM') === 0) {
			return 'bmp';
		}

		return null;
	}

}