I/O Utilities¶

Python bindings for src/theia/io: reconstruction import/export, Bundler/NVM/COLMAP-style writers, and NeRF/SDF studio JSON. All symbols below live on pytheia.io (submodule defined in io.cc).

Convention: read helpers exposed from io_wrapper.h return a leading bool success flag, then loaded objects. Write functions return bool directly (except where noted).

Classes¶

`BundlerObservation`¶

One 2D observation of a Bundler 3D point: camera_index, feature_index, x, y.

`BundlerPoint`¶

Bundler 3D point: position, color, view_list (list of BundlerObservation).

`BundlerFileReader(lists_file, bundle_file)`¶

Low-level Bundler parser: call ParseListsFile() / ParseBundleFile() then inspect cameras(), points(), img_entries().

`BundlerCamera`¶

Fields: translation, rotation, focal_length, radial_coeff_1, radial_coeff_2.

`ListImgEntry`¶

List-file row: filename, second_entry, focal_length.

Reading / importing¶

Function	Returns	Description
`ReadReconstruction(input_file)`	`(ok, reconstruction)`	Binary Theia reconstruction (`reconstruction_reader.h`).
`ReadBundlerFiles(lists_file, bundle_file)`	`(ok, reconstruction)`	Noah Snavely Bundler lists + bundle.
`ImportNVMFile(nvm_filepath)`	`(ok, reconstruction)`	NVM_V3 text bundle (`.nvm`).
`Read1DSFM(dataset_directory)`	`(ok, reconstruction, view_graph)`	1DSfM layout: sparse geometry + view graph.
`ReadStrechaDataset(dataset_directory)`	`(ok, reconstruction)`	Strecha multi-view benchmark style data.
`PopulateImageSizesAndPrincipalPoints(image_directory)`	`(ok, reconstruction)`	Wrapper around `populate_image_sizes.h`: loads image files named by each view and sets camera size and center principal point. The Python binding passes a fresh empty `Reconstruction` into the C++ call (see `io_wrapper.cc`); it succeeds trivially if there are no views. After `ReadBundlerFiles`, you typically need image dimensions filled on that same reconstruction—use C++ or extend the binding if the empty-reconstruction path is insufficient.

Writing reconstructions and exchange formats¶

Function	Returns	Description
`WriteReconstruction(reconstruction, output_file, write_full_reconstruction=False)`	`bool`	Binary Theia format (`reconstruction_writer.h`). By default only estimated views and multi-view tracks are written; pass `write_full_reconstruction=True` for the complete model.
`WriteReconstructionJson(reconstruction, output_json_file)`	`bool`	JSON export of estimated views and tracks.
`WritePlyFile(ply_file, reconstruction, camera_color, min_num_observations_per_point)`	`bool`	PLY point cloud for MeshLab-style viewers (`write_ply_file.h`). `camera_color` is an `Eigen::Vector3i` (RGB); use a NumPy length-3 integer array from Python.
`WriteBundlerFiles(reconstruction, lists_file, bundle_file)`	`bool`	Bundler lists + bundle from a reconstruction.
`WriteNVMFile(nvm_filepath, reconstruction)`	`bool`	NVM text.
`WriteColmapFiles(reconstruction, output_directory)`	`bool`	COLMAP-compatible text under `output_directory`.
`WriteNerfStudio(path_to_images, reconstruction, aabb_scale, out_json_file)`	`bool`	`transforms.json`-style export (PINHOLE / FISHEYE mapping per `write_nerfstudio.h`).
`WriteSdfStudio(path_to_images, reconstruction, nearfar, radius)`	`bool`	SDFStudio JSON; PINHOLE, undistorted images (`write_sdfstudio.h`). `nearfar` is `(near, far)` floats.

Export to Nerfstudio¶

Writes a transforms.json compatible with Nerfstudio.

import pytheia as pt
ok = pt.io.WriteNerfStudio("/path/to/images", recon, 16, "/path/to/out/transforms.json")
# aabb_scale is typically 2, 4, 8, or 16

Notes: Supported camera models are mapped internally (PINHOLE and FISHEYE). Images are referenced as path_to_images/view_image_name.

Export to SDFStudio¶

Writes JSON compatible with SDFStudio. Images must be undistorted and PINHOLE.

import pytheia as pt
ok = pt.io.WriteSdfStudio("/path/to/images", recon, (2.0, 6.0), 1.0)
# nearfar is (near, far); radius controls scene radius

Not exposed in Python¶

The C++ tree also includes helpers such as WriteMatchesAndGeometry and WriteCalibration (write_matches.h, write_calibration.h) without pybind entries in io.cc. Use the C++ API or extend the bindings if you need those.