Issue in deer horns size detection

Hi there. I am new to Python and OpenCV, so I apologize if my problem is a bit obvious to you.

I google a way to measure size of horns of deer, antler, or other horns but what i found is how to measure exact height and width of shapes like rectangle tringle polygen etc but i’m not able to find or measure height and width of curve surface like horns.

Can anyone help me with my problem? Please. It can be with OpenCV or another way.

Greetings.

who is taking the images ?
any chance you can have a “reference object” with a known size in it ?

Thanks for your reply.
Yes right now i’m using 5*5 square box as a reference

i’m going to click image and then want to calculate size of horns

do you have an image to show us ? what have you tried so far ?