open3DCV : IO

Camera IO

camera.h

int read_camera(const std::string fname, Camera& camera);
int write_camera(const std::string fname, const Camera& camera);

camera IO method to read/write Camera data from/to a file fname.

Exif IO

exif_io.h

// to be done

method to extract focal length (pix) from EXIF tag.

When you take a photo with almost any digital camera, the camera embeds useful information about the photo into the JPEG file itself. This often includes information about exposure time, focus, aperture, whether the flash was activated, and focal length. The last of these, focal length, is especially useful when creating panoramas. This tutorial describing how to extract the focal length from the EXIF tags of a digital photo and to convert it to pixel units can be found here.

summarized steps

extract the EXIF tags: find focal length in mm
find the CCD width: find sensor/image width in mm
convert from millimeters to pixels: $\textbf{focal length in pixels = (image width in pixels) * (focal length in mm) / (CCD width in mm)}$

Keypoint IO

keypoint_io.h

int read_keypoints(const std::string fname, std::vector<Keypoint>& keypoints);
int write_keypoints(const std::string fname, const std::vector<Keypoint>& keypoints);

keypoint IO methods, which read/write Keypoint data from/to a file fname. The format of the file is as follows, note that all components but the first two are optional.

[x-coordinate] [y-coordinate] [scale] [orientation] [color] [image index]

Descriptor IO

descriptor_io.h

int read_descriptors(const std::string fname, std::vector<Vecf>& descriptors);
int write_descriptors(const std::string fname, const std::vector<Vecf>& descriptors);

descriptor IO methods, which read/write Descriptor data from/to file fname.

Match IO

match_io.h

int read_matches(const std::string fname, std::vector<DMatch>& matches);
int write_matches(const std::string fname, const std::vector<DMatch>& matches);

match IO methods, which read/write DMatch data to/from file fname. The format of the file is as follows:

[index of keypoint 1] [index of keypoint 2] [x-coordinate of keypoint 1] [y-coordinate of keypoint 1] [x-coordinate of keypoint 2] [y-coordinate of keypoint 2] [descriptor distance]

Graph IO

graph_io.h

int read_graph(const std::string fname, Graph& graph);
int write_graph(const std::string fname, const Graph& graph);

Graph IO methods, which read/write Graph data to/from file fname. The format of the file is as follows:

[number of images: I] [index of image 1] ... [index of image I]
[parameters of camera 1]
...
[parameters of camera I]
[number of tracks: T]
[number of keypoints in track 1: K_1] [x-coordinate of keypoint 1] [y-coordinate of keypoint 1] [image index of keypoint 1] ... [x-coordinate of keypoint K_1] [y-coordinate of keypoint K_1] [image index of keypoint K_1]
...
[number of keypoints in track T: K_T] [x-coordinate of keypoint 1] [y-coordinate of keypoint 1] [image index of keypoint 1] ... [x-coordinate of keypoint K_T] [y-coordinate of keypoint K_T] [image index of keypoint K_T]
[number of structure point: S]
[x-coordinate of struct_point 1] [y-coordinate of struct_point 1] [z-coordinate of struct_point 1]
...
[x-coordinate of struct_point S] [y-coordinate of struct_point S] [z-coordinate of struct_point S]

SfM IO

sfm_io.h

int write_sfm(const std::string dir, const Graph& graph)

method to write the camera parameters estimated by SfM to files that are compatible with existing MVS softwares, currently support PMVS.

open3DCV a lightweight Multiple View Geometry library

IO