#
# Demo 3b: One-step recursive normalized cuts with Ncut metric
#
# author: Christos Choutouridis <cchoutou@ece.auth.gr>
# date:   06/07/2025
#
try:
    from scipy.io import loadmat
    import matplotlib.pyplot as plt
    import numpy as np
    #Project requirements
    from image_to_graph import image_to_graph
    from normalized_cuts import n_cuts, calculate_n_cut_value
except ImportError as e:
    print("Missing package:", e)
    print("Run: pip install -r requirements.txt")
    exit(1)


def plot_split(image, labels, title, fname):
    M, N, _ = image.shape
    segmented = labels.reshape(M, N)
    plt.imshow(segmented, cmap='tab10', vmin=0, vmax=1)
    plt.title(title)
    plt.axis('off')
    plt.tight_layout()
    plt.savefig(fname)
    print(f"Saved: {fname}")
    plt.close()


def run_demo3b():
    data = loadmat("dip_hw_3.mat")

    for name in ["d2a", "d2b"]:
        img = data[name]
        print(f"\n=== Image {name} ===")

        affinity = image_to_graph(img)

        labels = n_cuts(affinity, k=2)
        ncut_val = calculate_n_cut_value(affinity, labels)

        print(f"  Ncut value: {ncut_val:.4f}")
        plot_split(img, labels, f"{name} - one step n_cuts (Ncut={ncut_val:.4f})", f"plots/demo3b_{name}_ncut.png")


if __name__ == '__main__':
    run_demo3b()