protected function getColumnWidths()
    {
        $first_row = reset($this->data);

        // Create an array with the columns as keys and values of zero
        $column_widths = $this->getDefaultColumnWidths($first_row);

        foreach ($this->data as $columns) {
            foreach ($columns as $key => $column) {
                $column_widths[$key] = $this->getCellWidth($column_widths[$key], $column);
            }
        }

        return $column_widths;
    }