PGPLOT Module: PGSTBG -- set text background color index


Set the Text Background Color Index for subsequent text. By default
text does not obscure underlying graphics. If the text background
color index is positive, however, text is opaque: the bounding box
of the text is filled with the color specified by PGSTBG before
drawing the text characters in the current color index set by PGSCI.
Use color index 0 to erase underlying graphics before drawing text.

TBCI (input) : the color index to be used for the background
for subsequent text plotting:
TBCI < 0 => transparent (default)
TBCI >= 0 => text will be drawn on an opaque
background with color index TBCI.