NOAA APT Splitter PoC

split.py

#!/usr/bin/env python3
from PIL import Image

import matplotlib.pyplot as plt


WEDGE_WIDTH = 45
WEDGE_END = 1040
WEDGE_START = WEDGE_END - WEDGE_WIDTH


THRESHOLD = -100

def average_wedgeline(img, y):
    avg = 0
    for cx in range(WEDGE_START, WEDGE_END):
            avg += float(img.getpixel((cx, y))) / WEDGE_WIDTH

    return avg


def read_wedges(img):
    wedges = []
    for wedge_id in range(0, 16):
        avg = 0
        for y in range(wedge_id * 8, (wedge_id + 1) * 8):
            avg += average_wedgeline(img, y) / 8.0
        wedges += [avg]

    return wedges


def adjust_brightness(zero_mod, max_mod, value):
    dyn_range = max_mod - zero_mod
    value = int(((value - zero_mod) / dyn_range) * 255)
    value = max(0, value)
    value = min(255, value)
    return value


def main():
    full_image = Image.open("example.png")
    w, h = full_image.size

    last_wedge = average_wedgeline(full_image, 0)
    averages = [last_wedge]
    diffs = [0]
    frame_count = 0
    for y in range(1, h):
        cur_wedge = average_wedgeline(full_image, y)
        averages += [cur_wedge]

        diff = cur_wedge - last_wedge
        diffs += [diff]

        if diff < THRESHOLD:
            start = y - 64
            end = y + 64
            print("Potential Frame: %d to %d" % (start, end))

            frame = full_image.crop(box=(0, start, w, end))

            wedges = read_wedges(frame)

            zero_mod = wedges[8]
            max_mod = wedges[7]

            wedges = [adjust_brightness(zero_mod, max_mod, wedge) for wedge in wedges]
            print("\tWedges: %s" % repr(wedges))

            pixels = frame.load()
            for x in range(0, 2080):
                for y in range(0, 128):
                    pixels[x,y] = adjust_brightness(zero_mod, max_mod, pixels[x,y])

            frame.save("frame%d.png" % frame_count)
            frame_count += 1

        last_wedge = cur_wedge


    plt.plot(averages)
    plt.plot(diffs)
    plt.show()


if __name__ == '__main__':
    main()