#
# handle an image upload
#
function handle_image_upload($key, $nick) {
  global $MAX_WIDTH, $MAX_HEIGHT, $SITE_BASE;

  $ret = '';

  # check to make sure image was even uploaded
  if ($_FILES[$key] && $_FILES[$key]['size'] > 0) {
    # build paths
    $tmp = $_FILES[$key]['tmp_name'];
    $safe_nick = preg_replace('/[^a-z0-9\-_]/', '_', $nick);
    $dest = "$SITE_BASE/files/pics/$safe_nick";

    # check image size
    list ($w, $h, $type, $attr) = getimagesize($tmp);
    if ($w > 600 || $h > 400) {
      # if the image is too large, scale it down
      $cmd = "/usr/bin/convert -scale 600x400 -antialias '$tmp' '$dest'";
      # print_r($cmd);
      system($cmd, $status); 
      if ($status != 0)
        return "";
    } else {
      # if the image isn't too large, just move it into place
      if (file_exists($dest))
        unlink($dest);
      if (!move_uploaded_file($tmp, $dest))
        return "";
    }

    # set return value
    $ret = "/files/pics/$safe_nick";
  }

  # return path (or nothing on error)
  return $ret;
}