How to calculate porosity using Imagej???

[sharmav]

Hey

I have light microscopy micro graphs of biomaterials, which I need to calculate the porosity of.

I am aware that I need to calculate the RGB % which would in turn give me the % of void space.

However, I am not able to figure it out. Can some one please help me out?

Have attached the micrograph along with this mail.

Would really appreciate it.

Cheers