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# Author: Johannes L. Schoenberger (jsch-at-demuc-dot-de)

# This script exports inlier matches from a COLMAP database to a text file.

import os
import argparse
import sqlite3
import numpy as np


def parse_args():
    parser = argparse.ArgumentParser()
    parser.add_argument("--database_path", required=True)
    parser.add_argument("--output_path", required=True)
    parser.add_argument("--min_num_matches", type=int, default=15)
    args = parser.parse_args()
    return args


def pair_id_to_image_ids(pair_id):
    image_id2 = pair_id % 2147483647
    image_id1 = (pair_id - image_id2) / 2147483647
    return image_id1, image_id2


def main():
    args = parse_args()

    connection = sqlite3.connect(args.database_path)
    cursor = connection.cursor()

    images = {}
    cursor.execute("SELECT image_id, camera_id, name FROM images;")
    for row in cursor:
        image_id = row[0]
        image_name = row[2]
        images[image_id] = image_name

    with open(os.path.join(args.output_path), "w") as fid:
        cursor.execute(
            "SELECT pair_id, data FROM two_view_geometries WHERE rows>=?;",
            (args.min_num_matches,))
        for row in cursor:
            pair_id = row[0]
            inlier_matches = np.fromstring(row[1],
                                           dtype=np.uint32).reshape(-1, 2)
            image_id1, image_id2 = pair_id_to_image_ids(pair_id)
            image_name1 = images[image_id1]
            image_name2 = images[image_id2]
            fid.write("%s %s %d\n" % (image_name1, image_name2,
                                      inlier_matches.shape[0]))
            for i in range(inlier_matches.shape[0]):
                fid.write("%d %d\n" % tuple(inlier_matches[i]))

    cursor.close()
    connection.close()


if __name__ == "__main__":
    main()