_DrawCross
_DrawCross(fBitmapRect.LeftTop() + BPoint(-1.0, -1.0), red);
_DrawCross(fBitmapRect.RightTop() + BPoint(1.0, -1.0), red);
_DrawCross(fBitmapRect.LeftBottom() + BPoint(-1.0, 1.0), red);
_DrawCross(fBitmapRect.RightBottom() + BPoint(1.0, 1.0), red);
void _DrawCross(BPoint where, rgb_color c);