NOAA APT sync marker finder

markers.py

#!/usr/bin/env python3
import sys

from PIL import Image

import matplotlib.pyplot as plt

SYNCA_SEQ = [False, False, False, False,
                          True, True, False, False,   # Pulse 1
                          True, True, False, False,   # Pulse 2
                          True, True, False, False,   # Pulse 3
                          True, True, False, False,   # Pulse 4
                          True, True, False, False,   # Pulse 5
                          True, True, False, False,   # Pulse 6
                          True, True, False, False,   # Pulse 7
                          False, False, False, False,
                          False, False, False, False];


SYNCB_SEQ = [False, False, False, False,
                          True, True, True, False, False,
                          True, True, True, False, False,
                          True, True, True, False, False,
                          True, True, True, False, False,
                          True, True, True, False, False,
                          True, True, True, False, False,
                          True, True, True, False, False,
                          False];


SYNC_LEN = 40
AVERAGE_ALPHA = 0.25

SYNC_THRESH = 35

def match_seq(buff, seq):
    pairs = zip(buff, seq)
    count = sum([1 if (x > 0 and y) or (x < 0 and not y) else 0 for x,y in pairs])

    return count


def main():

    img = Image.open(sys.argv[1])
    w, h = img.size

    img_color = img.convert('RGB')

    average = 0


    buff = [0.0] * SYNC_LEN
    for y in range(0, h):
        for x in range(0, w):
            cur_pixel = img.getpixel((x,y))

            sample = cur_pixel / 255.0

            average = AVERAGE_ALPHA * sample + (1.0 - AVERAGE_ALPHA) * average;
            sample = sample - average

            buff = buff[1:] + [sample]

            if match_seq(buff, SYNCA_SEQ) > SYNC_THRESH:
                print("A %d %d" % (x,y))
                img_color.putpixel((x,y), (255, 0, 0))
            elif match_seq(buff, SYNCB_SEQ) > SYNC_THRESH:
                img_color.putpixel((x,y), (0, 0, 255))
                print("B %d %d" % (x, y))

    img_color.save('marked.png')


if __name__ == '__main__':
    main()