export txt files with verified pairs

scripts/export_pairs_from_database.py

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+import sqlite3
+import argparse
+from pathlib import Path
+
+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 ExportMatches(
+    database_path: Path, 
+    min_num_matches: int, 
+    output_path: Path,
+) -> None:
+
+    if not output_path.exists():
+        print("Output folder does not exist")
+        quit()
+
+    connection = sqlite3.connect(database_path)
+    cursor = connection.cursor()
+
+    images = {}
+    pairs = []
+
+    cursor.execute("SELECT image_id, name FROM images")
+    for row in cursor:
+        image_id = row[0]
+        name = row[1]
+        images[image_id] = name
+
+    cursor.execute("SELECT pair_id, rows FROM two_view_geometries")
+    for row in cursor:
+        pair_id = row[0]
+        n_matches = row[1]
+        id_img1, id_img2 = pair_id_to_image_ids(pair_id)
+        id_img1, id_img2 = int(id_img1), int(id_img2)
+        img1 = images[id_img1]
+        img2 = images[id_img2]
+
+        if n_matches >= min_num_matches:
+            pairs.append((img1, img2))
+
+    with open(output_path / "pairs.txt", "w") as f:
+        n_pairs = len(pairs)
+        n_brute = 0
+        N = len(images.keys())
+        for x in range(1, N):
+            n_brute += N-x
+        print(f"n_pairs/n_brute: {n_pairs} / {n_brute}")
+
+        for pair in pairs:
+            f.write(f"{pair[0]} {pair[1]}\n")
+
+    connection.close()
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        description="Export pairs in a txt file from a COLMAP database."
+    )
+    parser.add_argument("-d", "--database", type=Path, required=True, help="Path to COLMAP database.")
+    parser.add_argument("-m", "--min_n_matches", type=int, required=True, help="Min number of matches that a pair should have after geometric verification.")
+    parser.add_argument("-o", "--output", type=Path, required=True, help="Path to output folder.")
+    args = parser.parse_args()
+
+    ExportMatches(
+        database_path=args.database,
+        min_num_matches=args.min_n_matches,
+        output_path=args.output,
+    )