I usually overlay a crosshair by using two lines. You just start with the coordinates you want at the center of the crosshair. The first line is x-delta,y to x+delta,y. The second line is x,y-delta to x,y+delta. Delta is the size of the crosshair in pixels.
If you want a really big crosshair, you can replace the delta terms with the image limits to get XMIN,y to XMAX,y and x,YMIN to x,YMAX. This crosshair is hard to miss.
If you are doing a live update and your crosshair is moving, you may need to clear existing overlays before adding the crosshair. I don't remember if a new acquisition will clear the overlays or not.
Bruce
Bruce Ammons
Ammons Engineering
