plot_annotated.py

import matplotlib.pyplot as plt
from PIL import Image

if __name__ == "__main__":
    image_path = "data/annotated/0164_swirl.jpg"
    label_path = "data/annotated/0164_swirl.txt"

    image = Image.open(image_path)
    width, height = image.size

    plt.imshow(image)
    plt.axis(False)

    with open(label_path, "r") as file:
        lines = [line.strip() for line in file if line.strip()]

    # each line is one annotated object: "<class_id> x1 y1 x2 y2 ... xn yn" with x/y normalized to [0, 1]
    for line in lines:
        values = line.split()
        coordinates = [float(v) for v in values[1:]]
        xs = [coordinates[i] * width for i in range(0, len(coordinates), 2)]
        ys = [coordinates[i] * height for i in range(1, len(coordinates), 2)]
        # give every vertex its own color via the colormap so the dots are visibly different
        colors = list(range(len(xs)))
        plt.scatter(
            xs,
            ys,
            c=colors,
            cmap="hsv",
            s=40,
            edgecolors="black",
            linewidths=0.5,
            zorder=2,
        )

    plt.show()