Added roundness measurement to blobs¶

• Since we are trying to match a round template with round holes, the correlation shape should be round
• might be useful to add a measurement of how round the blobs are
• Leginon code had a "moment of inertia" measurement, but this was not really implemented and looks abandoned
• one measure of how round the object is uses area and perimeter:
  

    roundness = 4 pi * area / perimeter**2
    for a circle, area = pi r**2
    perimeter = 2 pi r, so perimeter**2 = 4 pi**2 r**2
    and so perimeter**2 = 4 pi * area
  

• needed to modify the following files
  

  pyami/imagefun.py
  leginon/jahcfinder.py
  leginon/jahcfinderback.py
  leginon/jahcfindermodel.py
  leginon/targetfinder.py
  leginon/gui/wx/JAHCFinder.py
  leginon/leginondata.py
  

• perfect circle: 1.0
• square: 0.785
• line: approaches pi/len for large length: (pi * l)/(l**2 + 2l +1)
• a good starting point is 0.8
• set to 0.3 or less to include virtually everything
• implemented since October on Leginon at NYU