Table of contents
Understanding the challenge
This challenge gives us 3 files:
tortuga-example.png: PNG image data, 525 x 80, 8-bit/color RGB, non-interlaced
tortuga-example.txt: ASCII text
tortuga-flag.txt: ASCII text, with very long lines (824)
We need to create a script that draws vector-like images from the input provided in the flag.txt file
Solution
I create a new Python file.
I use matplotlib to graph the points which I represented as a numpy array
import matplotlib.pyplot as plt
import numpy as np
# Define the vector coordinates
vectors = [
# Draw triangle pointing down (drawn clockwise)
(2, 0), (-1, 2), (-1, -2),
# Skip
(0, 0), (3, 0),
# Draw triangle pointing up (drawn counterclockwise)
(-1, 2), (2, 0), (-1, -2),
# Skip
(0, 0), (1, 0),
] * 6
# Convert the vector coordinates to numpy arrays
vectors = np.array(vectors)
# Initialize current position
current_pos = np.array([0, 0])
skip = False
# Plotting
plt.figure(figsize=(8, 6))
for vector in vectors:
if vector[0] == 0 and vector[1] == 0:
skip = True
elif skip == True:
skip = False
current_pos += vector
else:
plt.plot([current_pos[0], current_pos[0] + vector[0]], [current_pos[1], current_pos[1] + vector[1]], 'b-')
current_pos += vector
plt.title('Flag')
plt.xlabel('X-axis')
plt.ylabel('Y-axis')
plt.axis('equal')
plt.show()
This works, but in the test example the triangles are inverted due to the script not taking into account the clockwise and anti-clockwise directions
I simply add this line:
vector[1] *= -1
below the for loop to invert the y coordinates.
This gives us the flag as a drawing:
FCSC{316834725604}