A character string identifying the
reference point for the text being drawn. The first character in
this string identifies the reference position in the "up" direction
and may be "B", "C" or "T". The second character identifies the
side-to-side reference position and may be "L", "C" or "R" (for
left, centre or right). The string is case-insensitive, and only
the first two characters are significant.
For example, a value of "BL" means that the bottom left point
of the original (un-rotated) text is to be drawn at the
position given by POS.