@wp, thanks. I suppose that's the math part, but I would also like to know how it would be done programatically with this imaging library.

Simple math: if the true size of the insect is S(cm, ins), the true size of the dime S(cm, dime), the pixel size of the insect S(pixels, ins), and the pixel size of the dime is S(pixel, dime) then

S(cm, ins) = S(cm, dime) * S(pixel, ins) / S(pixel, dime)

Let´s say I have an image of an insect and beside the insect I have also an object of know size (a dime , let´s say). So I know the size of the dime, from that size how would I go about calculating the size of the insect. Of course, I´m not looking for exact precision, but a close enough measurement would be good.

I hope that explains somewhat what I´m trying to achieve.

Thanks

I'm not really sure what are you trying to measure, maybe some illustrations could help?

Does anyone know how to use this library to get the measurements of an object in an image with a reference scale in the image? For example, I have an object known to be 5 cm wide, so another object's width beside it can be deduced.

Thanks
Javier