An interesting approach to measure porosity is to fit what is called the largest inscribed circle in a segmented image iteratively.

In the end, your image will have a lot of circles in it, of varying diameters. The distribution of those diameters gives you an idea of the porosity. More large circles is a porous image, more small circles, less porous. Tota number of circles is an estimate of clear area. I have a small ImageJ plugin to do this if you're interesting in trying it out. 

I'm looking for the publication that had made me adapt this plugin and if you're interested I will post it here. 

Best

EDIT: I've added the article. Regarding the small plugin, you will find a link to the JAR file which you can use from FIJI. 

To use: If you are not familiar with Fiji or ImageJ, I suggest you go to their website http://fiji.sc/ The following assumes you know what you are doing in Fiji. 

The plugin works either on a selection or on a binary image. Just run it a few times and see what it does. Let me know if I can help. Best

https://github.com/lacan/max-inscribed-circles/tree/master/dist

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Dear Olivier,

Please do post it as I need it urgent .

Thanks for your humble cooperation

If you only want to judge the porosity of the images it could be worth trying a simple segmentation on the images. Then you can just count the number of black and white pixels and you should see an increase in porosity.

I tried it with the right image and got a porosity of around 33%. I am aware that the left image will be harder to handle, but with some smart filters it might still be the way to go.

This method is very quick and gives you an idea of the overall porosity in your image.

Thanks Ralph but in my case black pixel may be because of some reinforcement,then how to handle that.

If possible just have a look at one of my optical images, it would be a great help

hi again,

I was thinking of something like the segmented image attached. It gives me a porosity of 32%. I cannot judge the influence of the reinforcements, but if that is a third phase than you can simply do the segmentation with three phases instead of two.

Also in case the segmented image show a lot of small pixels in the bulk you could try methods like opening/closing to get rid of them.

Good luck

Dear Dr. Sharma,

You can use metallographic software such as Dewinter Material Plus to analyse the porosity through ASTM B276. Alternatively, you can also analyse the porosity in by ImageJ software tool. ImageJ is available freely (follow the link below).

Please see the attachment for help on ImageJ.

I hope it helps

With Best Regards,

Sunny Zafar

http://imagej.net/Welcome