Darknet support

[pcuenca]

Thanks a lot for this, guys, it works great for quick tests of various models.

I wonder if you have considered extending the backend to also support Darknet. I know there are various conversion tools to Keras or TensorFlow, but I'd rather drop the native model files and use the darknet library instead of having to go through additional steps.

If you don't mind me doing it, I can take an initial look at how such an extension could work.

Congratulations anyway for your work!

[jmplaza]

Great @pcuenca ! Your contributions in this topic are more than welcome.

It was on the roadmap, to extend the supported neural networks frameworks in ObjectDetector. Maybe the main challenge is to integrate Darknet support, which is C++ code, into Python code of ObjectDetector. We solved the opposite (use Python frameworks from C++ code) in DetectionSuite.

Thanks for your contributions, they will be very useful.

[pcuenca]

That's great news!

The Python -> Darknet integration is already working in Pull Request #39, which I submitted before. I need to improve a few things (dataset configuration, mostly), but that branch can already be used for testing. I used YOLOv3-tiny as an example, and it seems to work fine. If you have any comments, questions or suggestions, please let me know.