Combiner for /r/place frames.

combine.py

# Requires PyPNG (https://pypi.python.org/pypi/pypng)

import png
from collections import defaultdict
import sys
import glob

# Colour palettes are in different orders on images. Convert to standard palette.
STANDARD_PALETTE = [(0, 0, 234), (0, 131, 199), (0, 211, 221), (2, 190, 1), (34, 34, 34), (130, 0, 128), (136, 136, 136), (148, 224, 68), (160, 106, 66), (207, 110, 228), (228, 228, 228), (229, 0, 0), (229, 149, 0), (229, 217, 0), (255, 167, 209), (255, 255, 255)]
PALETTE_MAP = {x: i for i, x in enumerate(STANDARD_PALETTE)}

# Loads an image and yields 1M pixels (indexes into palette).
def loadImageToGenerator(fn):
  f = open(fn, 'rb')
  r = png.Reader(file=f)
  width, height, pixels, metadata = r.read()

  palette = metadata['palette']
  for row in pixels:
    for p in row:
      # Standardize pixel colour palette.
      yield PALETTE_MAP[palette[p]]

def mergePixels(pixels):
  # Uncomment line below for desired algorithm

  d = defaultdict(int)
  for i, p in enumerate(pixels):
    # Simple FPTP
    # d[p] += 1
    # Weighted towards later images
    d[p] += i + 1

  # In case of tie, higher index in colour palette is chosen.
  return max((b, a) for a, b in d.items())[1]

def mergeFilesToIterator(fns):
  fns.sort()

  # FUNCTIONAL PROGRAMMING!!!
  return map(mergePixels, zip(*map(loadImageToGenerator, fns)))

def iteratorToRowIterator(it, cols=1000):
  while True:
    yield [it.__next__() for i in range(cols)]

if __name__ == '__main__':
  if len(sys.argv) < 2:
    pathname = '*.png'
  else:
    pathname = sys.argv[1]

  fns = glob.glob(pathname)
  print('Combining {} files...'.format(len(fns)))

  w = png.Writer(width=1000, height=1000, bitdepth=4, palette=STANDARD_PALETTE)
  of = open('output.png', 'wb')
  w.write(of, iteratorToRowIterator(mergeFilesToIterator(fns)))
  of.close()