2-edge.py

# Gaussian blur — sigma controlled by ksize (must be odd) and sigmaX
blurred = cv2.GaussianBlur(image, ksize=(5, 5), sigmaX=1.4)
 
# Sobel gradients in x and y
Gx = cv2.Sobel(blurred, cv2.CV_64F, dx=1, dy=0, ksize=3)
Gy = cv2.Sobel(blurred, cv2.CV_64F, dx=0, dy=1, ksize=3)
 
# Gradient magnitude
magnitude = np.sqrt(Gx**2 + Gy**2)
magnitude = (magnitude / magnitude.max() * 255).astype(np.uint8)
 
fig, axes = plt.subplots(1, 2, figsize=(10, 4))
for ax, img, title in zip(axes, [blurred, magnitude], ['Gaussian blur (σ=1.4)', '|∇f| - Sobel magnitude']):
    ax.imshow(img, cmap='gray')
    ax.set_title(title)
    ax.axis('off')
plt.tight_layout()
plt.show()