Making use of the Fourier Ring Correlation Implementation by Alex Herbert
which is itself 'adapted from the FIRE (Fourier Image REsolution) plugin produced as part of the paper
Niewenhuizen, et al (2013). Measuring image resolution in optical nanoscopy. Nature Methods, 10, 557
http://www.nature.com/nmeth/journal/v10/n6/full/nmeth.2448.html