Measure porosity in a irregular/polygon selection

I want to measure the porosity of the weld zone, which is not a standard rectangular (as shown in LW-56-1).
Anyone got a solution for it?


How do you compute porosity ? area of holes/area of ROI ?
You can get the holes with an MaxEntropy threshold on a casted 8 bit version of your image. The Edit>Selection>Create Selection allows to select them.
The Analyze>Measure allows to get the area of holes and ROI. For your image, porosity is ~5%