function getimagepng($base64_string){
$im = base64_decode($base64_string);
$filename = “/tmp/”;
$filename .= uniqid(“intrinsic_”).”.png”;

  $file = fopen($filename, “wb”);
  $newIamge = resize_image($im, 500, 500);

  fwrite($file, $newIamge);
  fclose($file);
  return $filename;
}

function resize_image($file, $w, $h, $crop=FALSE) {
  //list($width, $height) = getimagesize($file);
  $src = imagecreatefromstring($file);
  if (!$src) return false;
  $width = imagesx($src);
  $height = imagesy($src);

  $r = $width / $height;
  if ($crop) {
      if ($width > $height) {
        $width = ceil($width-($width*abs($r-$w/$h)));
      } else {
        $height = ceil($height-($height*abs($r-$w/$h)));
      }
      $newwidth = $w;
      $newheight = $h;
  } else {
      if ($w/$h > $r) {
        $newwidth = $h*$r;
        $newheight = $h;
      } else {
        $newheight = $w/$r;
        $newwidth = $w;
      }
  }
  //$src = imagecreatefrompng($file);
  $dst = imagecreatetruecolor($newwidth, $newheight);
  imagecopyresampled($dst, $src, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);

  // Buffering
ob_start();
imagepng($dst);
$data = ob_get_contents();
ob_end_clean();
  return $data;
}