Detecting WEBP format and dimensions of picture (width and height of image) with PHP, without libraries

Sunday, March 3, 2019

function is_webp($hdr) {

  return substr($hdr, 0, 4) == 'RIFF' &&

         substr($hdr, 8, 4) == 'WEBP';

}

// Getting width and height of WEBP image PHP's GD lib. Works even in PHP lower than v5.5.

function get_webp_size($fn) {

  $w = 0;

  $h = 0;

  if ($f = @fopen($fn, 'rb')) {

    $hdr = fread($f, 32);

    fclose($f);

    if (strlen($hdr) >= 30) {

      $w = unpack('C3b', substr($hdr, 24, 3));

      $w = ($w['b1'] + $w['b2']*256 + $w['b3']*65536) + 1;

      $h = unpack('C3b', substr($hdr, 27, 3));

      $h = ($h['b1'] + $h['b2']*256 + $h['b3']*65536) + 1;

    }

  }

  return array($w, $h);

}