Pore size ,pore diameter calculation and using image j to calculate the porosity of the SEM image

Hello I am a new user of image j . I wanted to calculate the pore sizes of the sem image and the pore diameter also the porosity, I donot know If I am doing it wrong or not I first change the SEM image to the black and white and then did the particle analysis. However it is giving me the counts of the grains in it and not the voids in the black I guess ,correct me if I am wrong.
Also I invert the picture after thershoulding but didn’t worked thershoulding is the main thing in this SEM image if some one can guide me. I would be so thankfull to him.And can share the correct threshold picture with me and process of how he did it.

Dear Khattak,
You might need a better SEM micrograph since this one doesnt look good enough for analysis in my opinion.

Hello faruuk,
well this is the one day sample but I will share a 7 days sample which is more clear and good for analysis . looking forward for your comments and process method.

Hello @M.khattak

Looking at your image I can’t really tell which part is void and which is not. Maybe you can draw the segmentation by hand for this example image. Then others, which don’t work in this field understand what you are looking for and are probably able to help.

A problem which I might occur, is the meta-data bar at the bottom. If you want to use a automatic threshold method, you first have to remove this bar.

the image the white spots are the grains and black as some how void as I have been told.
For thershoulding I use the FFT and then bypass filter, and after these steps I go for the thershoulding .which gives me a black and white image. however the problem with it is the when I do particle analysis the white spots some are outline and not all keeping the value of circularity between 0 -1.
I will share images of it . how should I measure the black spots .Is it by inverting the image CTRL.SHIFT,I . I did it too but however I think I have an issue of the proper thershoulding .
how can I do the steps for the hand segmentation.?
And how to do the automatic thershoulding method and removing the bar.
thanks for the help

this is the thershoulding image after using the FFT BANDPASS filter .

this the particle analysis by not inverting it. how should I make it select all the particles with good circularity or polygon select it for me.
kindly guide me on the steps of how should I only measure the black spots and process for segmentation so that my all particle are analyised and can show me in outlines.