I didn't mean that. Actually, I wanted to know is there any plug in for distinguishing cracks from pores to calculate the area fraction of cracks only.
I know this is an old thread, I would defintely recommend you visit www.MIPAR.us. I think it would work perfectly for your needs.
It is very powerful and intuitive 2D/3D image analysis software written by scientists/end-users and is about to be released as a free trial on December 14th. You can sign up on the site as well as submit images/datasets to test.
There are many image analysis options available, but I think you may just find MIPAR to be something special if you give it a try!