measure distance

[卡卡西]

HI
Can someone help me
I want to measure distance.
The image is white and looks like an cirque, and I want to  measure the thickness from  the Image.

I had thought I move the origin into center of image, and get any angle edge point coordinates in an array.Then perhaps the program could get  the distance from any angle.(but how can I get the edge coordinates?)
thanks!

kakaxi

[卡卡西]

the image

[Kalanga]

do u want to measure the thickness of the circular line or anything else?

[卡卡西]

I want to measure the thickless as the arrow shows(There is not arrow in quondam image,that is addition to show you which needs to measure)

thanks