convert -thumbnail ${image_size} "${target_file}" "${output_file}"
elif [[ x"${cmd_type}" = "x" ]] ; then
  echo "No filetype."
  exit 1
else
  echo "Unsupported type: ${cmd_type}"
  exit 1
fi

if [[ ! -f ${output_file} ]] ; then
  echo "Thumbnail is not created."
  exit 1