Intento fallido de capturar el contorno de una imagen

contour.py

# -*- coding: utf-8 -*-
from PIL import Image
from PIL import ImageFilter


# Get an image
image = Image.open('images/image.jpg')

# Get the contour
image = image.filter(ImageFilter.CONTOUR)

# Save image
image.save('images/image_contour.jpg')

# Show image
image.show()

image_converter.py

# -*- coding: utf-8 -*-
from PIL import Image
import numpy as np
import matplotlib.pyplot as plt

# Read image to array
image = np.array(Image.open('images/image.jpg').convert('L'))

# Create a new figure
plt.figure()

# Convert to gray scale
plt.gray()

# Take contours with origin upper left corner
plt.contour(image, origin='image')
plt.axis('equal')
plt.axis('off')

# Show image
plt.show()

shape.py

# -*- coding: utf-8 -*-
from PIL import Image
from PIL import ImageChops
from PIL import ImageOps    

# Get an image
image = Image.open('images/image.jpg')

# Convert image to black and white
convert_gray = image.convert('L')
black_and_white_image = convert_gray.point(lambda x: 0 if x < 128 else 255, '1')
black_and_white_image.save('images/image_bw.jpg')
imported_bw_image = Image.open('images/image_bw.jpg')

# Invert colors 
inverted_image = ImageOps.invert(imported_bw_image)
inverted_image.save('images/image_inv.jpg')

# Darken new image
image = Image.open('images/image.jpg')
darken_image = image.point(lambda x: x * 0.5)
darken_image.save('images/image_dark.jpg')

# Subtract images
imported_darken_image = Image.open('images/image_dark.jpg').convert('CMYK')
imported_inverted_image = Image.open('images/image_inv.jpg').convert('RGBA')
diff = ImageChops.difference(imported_inverted_image, imported_darken_image)
diff.save('images/result_image.jpg')