Measuring an object from a picture using a known object size

Question

So what I need to do is measuring a foot length from an image taken by an ordinary user. That image will contain a foot with a black sock wearing, a coin (or other known size o

Answer 1

I am not sure if you need to build this yourself, but if you just need to do it, and not code it. You can use KLONK Image Measurement for this. There is a free and payable versions.