image = cv2.imread("0.0/01.pgm", cv2.COLOR_BGR2GRAY)


def get_coords_by_threshold(image: np.ndarray, threshold: int = 150) -> tuple:
    """Gets pixel coords with intensity more then 'theshold'."""
    coords = np.where(image > threshold)
    return coords


def delete_pixels_by_min_threshold(
        image: np.ndarray, min_threshold: int = 100
) -> np.ndarray:
    """Deletes coords from image and returns this image."""
    anti_coords = np.where(image < min_threshold)
    image[anti_coords] = 0
    return image


def get_neigh_nums_list(
        coords: tuple, kernel_size: int = 3
) -> list:
    """
    Gets list with number of neighborhoods by kernel.
    Returns list like [[x1, y1, N1], [x2, y2, N2]],
    Where N - neighborhood's number.
    """
    neigh_nums = []
    offset = (kernel_size - 1) // 2

    for x, y in zip(coords[0], coords[1]):
        if x < 0 + offset or x > image.shape[0] - offset:
            continue
        if y < 0 + offset or y > image.shape[1] - offset:
            continue
        
        kernel = image[x-offset:x+offset+1, y-offset:y+offset+1]
        step_neigh_num = np.count_nonzero(kernel) - 1
        neigh_nums.append([x, y, step_neigh_num])

    return neigh_nums


def sort_neight_nums_by_N(neigh_nums: list) -> np.ndarray:
    """
    Sort neigh_nums by N parameter.
    Removes N=-1, N=0 and sorts by N desc. 
    """
    np_neigh_nums = np.array(neigh_nums)

    np_neigh_nums = np_neigh_nums[
        (np_neigh_nums[:, 2] != -1) & (np_neigh_nums[:, 2] != 0)]

    np_neigh_nums = np_neigh_nums[
        np.argsort(-np_neigh_nums[:, 2])]

    return np_neigh_nums


def get_potential_points_coords(
        sorted_niegh_nums: np.ndarray, potential_points_num: int = 30
) -> np.ndarray:
    """
    Gets best candidates, potential points coords only.
    Returns np.ndarray like [[x1, y1], [x2, y2]].
    """
    sorted_neigh_nums = np.delete(sorted_niegh_nums, 2, axis=1)
    return sorted_neigh_nums[:potential_points_num]


def get_best_lines(potential_points: np.ndarray) -> np.ndarray:
    """
    Gets best combinations of lines by all points.
    Line y = kx + b.
    Returns np.ndarray like [[k1, b1], [k2, b2]].
    """
    best_lines = []
    best_inliers = []
    iterations_num = 1000
    threshold_distance = 3
    
    for i in range(iterations_num):
        sample_indices = np.random.choice(potential_points.shape[0], size=3, replace=False)
        
        sample_points = potential_points[sample_indices]
        sample_x = sample_points[:, 1]
        sample_y = sample_points[:, 0]
        
        coefficients = np.polyfit(sample_x, sample_y, deg=1)
        
        distances = np.abs(potential_points[:, 0] - np.matmul(np.vstack((potential_points[:, 1], np.ones_like(potential_points[:, 1]))).T, coefficients)) / np.sqrt(coefficients[0] ** 2 + 1)
        inliers = np.where(distances < threshold_distance)[0]

        if len(inliers) > len(best_inliers):
            best_lines = [coefficients]
            best_inliers = inliers
        elif len(inliers) == len(best_inliers):
            best_lines.append(coefficients)
    
    return np.array(best_lines)



# main
coords = get_coords_by_threshold(image)

image = delete_pixels_by_min_threshold(image)

neigh_nums = get_neigh_nums_list(coords)

sorted_neigh_nums = sort_neight_nums_by_N(neigh_nums)

potential_points = get_potential_points_coords(sorted_neigh_nums)

best_lines = get_best_lines(potential_points)
print(best_lines)

# Visualization
plt.imshow(image, cmap="gray")
plt.scatter(potential_points[:, 1], potential_points[:, 0], color="red", marker="o")
plt.show()

# Plot the lines on the image
for equation in best_lines:
    k, b = equation
    x = np.arange(0, image.shape[1])
    y = k * x + b
    plt.imshow(image, cmap="gray")
    plt.scatter(potential_points[:, 1], potential_points[:, 0], color="red", marker="o")
    plt.plot(x, y, color="green")
    plt.scatter(potential_points[:, 1], potential_points[:, 0], color="red", marker="o")
plt.show()

Отлично, только алгоритм нашел самые качественные прямые, которые очень близко к друг другу (почти одинаковые прямые), а нужно три самых качественных, так как мы детектируем треугольник, то есть нужно выбрать самые качественные три прямые, не похожие по k, b