WSxM might be good for analyzing files directly from AFM? but it does not seem to work well with files that are of more common formats (png tif jpg) or even those exported from Gwyddion in formats that should hopefully have been openable in WSxM (.spm and .stp).  While it is freeware for analyzing scanning probe images it seems to require that the images be sourced from equipment, not random image files gathered from various sources (as i have done while assessing SP-D).  In terms of ease of use, I personally would rate it – not fun and while the screen print below shows that in fact at one point i was able to import an image (exported via gwyddion as an ascii file) there was no benefit that I could find in using this software for the purpose of plotting peaks and valleys along the SP-D arms.  In all fairness, I did not use it according to its purpose was thought it was worth the effort to investigate it since Arroyo et al used it for their plots of AFM images. Image on the left is from Arroyo et al ( a tiff) imported into gwyddion, exported as ascii from gwyddion.  You can see that the one time i was able to open it in WSxM there was virtually no way to see processing the image as a benefit to those programs already in use.

With all due respect to the developers, it was my mistake to try to use this program and my pic for image processing remains the two versions of CorelDRAW (x5 and 19) and ImageJ.