I have an imperfect shape and I need to know the circumference of half of it.

I am working on a computer programme which unfortunately does not allow you to measure curves, only straight lines and I need to fit one curved shapes circumference to match that of another curved shape.

If I can work out the radius and diameter of a shape (which I can do with straight lines) then should I be able to work out the circumference also?

Once I have worked out the circumference I then want to know how to increase/ decrease it so that both shapes circumferences are of the same value.

I am working on a computer programme which unfortunately does not allow you to measure curves, only straight lines and I need to fit one curved shapes circumference to match that of another curved shape.

If I can work out the radius and diameter of a shape (which I can do with straight lines) then should I be able to work out the circumference also?

Once I have worked out the circumference I then want to know how to increase/ decrease it so that both shapes circumferences are of the same value.