def convert_l_to_rgba(self, row, result):
        """
        Convert a grayscale image to RGBA.

        This method assumes the alpha channel in result is already
        correctly initialized.
        """
        for i in range(len(row) // 3):
            for j in range(3):
                result[(4 * i) + j] = row[i]
Convert a grayscale image to RGBA.

        This method assumes the alpha channel in result is already
        correctly initialized.