# Python script for Golly to count active cells within the envelope of a moving pattern

count_active.py

#count_active.py
# Count active cells within the envelope of a moving pattern
import golly as g
import numpy as np

r = g.getrect()
if not r:
  g.exit('No pattern')
patt = g.getcells(r)

if len(patt)%2:
  g.exit('Only 2-state patterns supported')

# Check every second generation for roomba bugs
g.setbase(2)
g.setstep(1)

# keep track of cells within envelope which have been On or Off
sz = (104, 104) # large enough to fit the pattern when centred
everOn = np.zeros(sz, dtype=bool) # Cells which have been On in any generation
allOn = np.ones(sz, dtype=bool) # Cells which have been On in every generation
allOff = np.ones(sz, dtype=bool) # Cells which have been Off in every generation
active_count = []

# loop over successive even generations
for ii in xrange(1, 50001):
  r = g.getrect()
  if not r:
    g.exit('Pattern has become empty')
  patt = g.getcells(r)
  ncells = len(patt)/2
  
  # Centre pattern using centre of mass
  xmean = int(round(float(sum(patt[0::2])) / ncells))
  ymean = int(round(float(sum(patt[1::2])) /  ncells))
  patt = g.transform(patt, 52-xmean, 52-ymean)
  npPatt = np.zeros(sz, dtype=bool)
  for (x,y) in zip(patt[0::2], patt[1::2]):
    npPatt[x, y] = True
  
  everOn |= npPatt
  allOn &= npPatt
  # allOff &= ~npPatt # equivalent to ~everOn
  
  g.step()
  if not (ii % 1000):
    g.update()
    active_count.append(everOn.sum() - allOn.sum())
    g.show(str(active_count[-20:]))

# count_everOn = everOn.sum()
# count_allOn = allOn.sum()
# count_allOff = allOff.sum()

# g.show(str([count_everOn, count_allOn, count_everOn-count_allOn]))
g.note(str(active_count))