Write UTF-8 image names intact in COLMAP binary models

nerfstudio/data/utils/colmap_parsing_utils.py

@@ -300,8 +300,7 @@ def write_images_binary(images, path_to_model_file):
             write_next_bytes(fid, img.qvec.tolist(), "dddd")
             write_next_bytes(fid, img.tvec.tolist(), "ddd")
             write_next_bytes(fid, img.camera_id, "i")
-            for char in img.name:
-                write_next_bytes(fid, char.encode("utf-8"), "c")
+            fid.write(img.name.encode("utf-8"))
             write_next_bytes(fid, b"\x00", "c")
             write_next_bytes(fid, len(img.point3D_ids), "Q")
             for xy, p3d_id in zip(img.xys, img.point3D_ids):

tests/process_data/test_colmap_binary_image_names.py

@@ -0,0 +1,24 @@
+from pathlib import Path
+
+import numpy as np
+
+from nerfstudio.data.utils.colmap_parsing_utils import Image, read_images_binary, write_images_binary
+
+
+def test_multibyte_image_name_roundtrip(tmp_path: Path):
+    image = Image(
+        id=7,
+        qvec=np.array([1, 0, 0, 0]),
+        tvec=np.zeros(3),
+        camera_id=3,
+        name="室内/café.png",
+        xys=np.array([[2.5, 1.0]]),
+        point3D_ids=np.array([17]),
+    )
+    path = tmp_path / "images.bin"
+    write_images_binary({image.id: image}, path)
+    restored = read_images_binary(path)[image.id]
+
+    assert restored.name == image.name
+    np.testing.assert_array_equal(restored.xys, image.xys)
+    np.testing.assert_array_equal(restored.point3D_ids, image.point3D_ids)