Automatically measure features in an image?

[cantab]

Not sure where's the best place to ask this (probably not kubuntuforums.net, but I'm registered here, so...)

I have some electron micrographs of magnetite powders (see attached), and I want the particle size distribution. So I'm after an easier (and less error-prone) method than taking a ruler to the image and measuring them all manually.

Any idea for a way to do this? It's probably a bit much to expect anything completely automagic, but say I were to trace the edges manually and then have a way to get the dimensions of all the polygons thus produced, even that would help a lot (especially as I have access to a graphics tablet)

EDIT: Image attached. I had to crop it to meet attachment size limits.

[dibl]

Re: Automatically measure features in an image?

Interesting question!

Gimp has a "measuring tool" in the toolbox, and my quick little skim of it indicates you can set it to a variety of metrics, including mm, cm, inches, feet, picas, pixels, etc. It measures angles too. So I would say you have some hope in that direction.