Improve documentation of FT_BBox.
diff --git a/include/freetype/ftimage.h b/include/freetype/ftimage.h
index 618c172..334dc39 100644
--- a/include/freetype/ftimage.h
+++ b/include/freetype/ftimage.h
@@ -99,6 +99,16 @@ FT_BEGIN_HEADER
/* */
/* yMax :: The vertical maximum (top-most). */
/* */
+ /* <Note> */
+ /* The bounding box is specified with the coordinates of the lower */
+ /* left and the upper right corner. In PostScript, those values are */
+ /* often called (llx,lly) and (urx,ury), respectively. */
+ /* */
+ /* If `yMin' is negative, this value gives the glyph's descender. */
+ /* Otherwise, the glyph doesn't descend below the baseline. */
+ /* Similarly, if `ymax' is positive, this value gives the glyph's */
+ /* ascender. */
+ /* */
typedef struct FT_BBox_
{
FT_Pos xMin, yMin;