How to manipulate annotation arrow (<->)

Hi,

I’m quite new to python and matplotlib so please forgive me if this quite basic.

I need to annotate a distance on a image by a two arrowed bar. I tried using arrowprops with arrowstyle = ‘<->’ and connectionstyle=‘bar’ but I could find how to have the text above the bar and not at the edge of the bar.

Could someone drop clue?

Thanks,

OrenG