Opencv_contrib: sfm reconstruct not available in python bindings

[miguelriemoliveira]

Hello

I am trying to use the sfm module from python3.

I can run the reconstruct example like this

./example_sfm_trajectory_reconstruction desktop_tracks.txt 1914 640 360

and I can compile a cpp file with that code as well after using the tips from #476

However, in python, when I import the cv2 module I cannot find the reconstruct method, e.g.,

import cv2
help(cv2.sfm)

displays the following stuff

Basically it seems all sfm functions are available except the sfm.reconstruct.

This is a very similar issue to #476 but the solution in that case for cpp does not work in python.

Any help would be appreciated.

Miguel

[miguelriemoliveira]

I found the answer so I will share it.

The reason is that the definition of the reconstruct function in the modules/sfm/include/opencv2/sfm/reconstruction.hpp file

is defined with the

CV_EXPORTS, e.g.,

CV_EXPORTS
void
reconstruct(InputArrayOfArrays points2d, OutputArray Ps, OutputArray points3d, InputOutputArray K,
bool is_projective = false);

and the CV_EXPORTS flag does not export python bindings, see here:

"All external functions and classes must use CV_EXPORTS, otherwise there will be linking errors on Windows. For functions/classes which you want to expose in Python, Java etc. you should use CV_EXPORTS_W instead of CV_EXPORTS, but please be careful with overloaded functions and methods, with non-standard parameter types etc."

So I changed from CV_EXPORTS to CV_EXPORTS_W, recompiled and reinstalled opencv and it works.

I do not know why the author of this code "decided" to not use the python bindings, perhaps because of some problem I will encounter further ahead ...

Could not add CV_EXPORTS_W to the overloaded reconstruct methods which had as arguments
const std::vectorstd::string images

[johncant]

@miguelriemoliveira - thankyou for posting those changes. Do you have any working python examples using these functions?

[miguelriemoliveira]

Hi @johncant . Sorry, I do not. Best of luck.

[ddrmorais]

@miguelriemoliveira - thankyou for posting those changes. Do you have any working python examples using these functions?

Hi @miguelriemoliveira,
Thanks for sharing this post. I have used your instructions and It has run.
After running, Where can I find these functions in the HD? I want to know what are the functions I can use in python therefore the examples mentioned by @johncant would be important.