4-edge.py

def run_canny(image, sigma, t_low, t_high, aperture=3):
    """Apply Gaussian blur then Canny edge detection."""
    # Kernel size: 2 * ceil(3*sigma) + 1 ensures the kernel covers ±3σ
    ksize = 2 * int(np.ceil(3 * sigma)) + 1
    blurred = cv2.GaussianBlur(image, (ksize, ksize), sigmaX=sigma)
    edges = cv2.Canny(blurred, threshold1=t_low, threshold2=t_high, apertureSize=aperture)
    return edges

edges = run_canny(image, sigma=1.4, t_low=50, t_high=150)

fig, axes = plt.subplots(1, 2, figsize=(10, 4))
axes[0].imshow(image, cmap='gray')
axes[0].set_title('Original')
axes[0].axis('off')
axes[1].imshow(edges, cmap='gray')
axes[1].set_title('Canny edges (σ=1.4, T_low=50, T_high=150)')
axes[1].axis('off')
plt.tight_layout()
plt.show()