Create a coding program that measures lengths

I am measuring parts of microscopic materials on slides. I want a program that would automatically put a scale bar and adjust the scale bar into the slide and give an accurate measurement of a smaller material on the photo. The scale bar is at the bottom of the stacked images. I want the scale bar to be replicated and able to move according to the shape of the object on the slide needed to be measured. I don't want to do this by hand, it takes forever because I have to keep moving the scale bar and make guesses which are terrible. The things measured on the slide are not always straight lines, they can bend. That is where it gets confusing, so the scale bar would need to bend also.