INVERT_P([G], [x1, y1], [x2, y2])
Inverts the rectangle on G defined by the diagonal points (x1,y1) and (x2,y2). The effect is reverse video.
The following values are optional and their defaults are listed:
x1, y1=top left corner of G
x2, y2=bottom right corner of G
If only one (x,y) pair is specified, it refers to the top left corner of G.
INVERT_P — Discussion