Drawing the flag for Hitcon's 2019 qualifications EV3 arm challenge

ev3_arm_solution.py

from PIL import Image, ImageDraw

import math

lines = open('movements.txt').readlines()

drawing = False
(pen_x,pen_y) = (80,150)
(base_x,base_y) = (200, 150)
cnt = 0
import re

def move(how_much, drawing):
    global pen_x, pen_y, base_x, base_y
    if drawing:
        draw.line((pen_x, pen_y, pen_x + how_much, pen_y), fill=0)
    pen_x += how_much


def line(degrees, drawing):
    # draw a line
    global pen_x, pen_y#, base_x, base_y
    new_y = pen_y + degrees

    if drawing:
        draw.line((pen_x, pen_y, pen_x, new_y), fill=0)

    pen_y = new_y
    print('new pen_y {}'.format(pen_y))

mul = 15
img = Image.new('RGB', (2000, 300), (255,255,255,255))
draw = ImageDraw.Draw(img)
for l in lines[1:]:
    if 'port_motor: B' in l:
        if 'speed: -15' in l:
            drawing = True
        elif 'speed: 15' in l:
            drawing = False
    if 'port_motor: C' in l:
        m = re.search('rotations:\s([0-9\.]+)', l)
        px = float(m.groups(1)[0])*mul
        #print (px)
        if 'speed: -' in l:
            px = -px
        move(px, drawing)
    if 'port_motor: A' in l:
        m = re.search('rotations:\s([\-0-9]+)', l)
        px = int(m.groups(1)[0])/360.0*mul
        if 'speed: -' not in l:
            px = -px
        line(px, drawing)
        cnt += 1
img.save('flag.png')