Make flipped an alias for flipHorizontal

[ziyuan-linn]

This PR adds flipped as an alias for flipHorizontal.

• Adds alias feature to handleOptions function. An alias property can now be provided to the moldObject, which sets an alias name for an option.
• Changes the mold objects of handPose, faceMesh, bodyPose, and bodySegmentation to include flipped as an alias for flipHorizontal.

TODO:
The MoveNet model does not support a flipHorizontal option natively. For MoveNet, we could try to flip the key-points in ml5 when flipped or flipHorizontal is set to true.

[shiffman]

This is great @ziyuan-linn! Shall we add it to the examples (or a selection of examples)? I think it might be nice for the examples, for the most part, to flip the video by default?

[ziyuan-linn]

I agree that the examples should have flipped videos by default when possible!

[shiffman]

Great! I'm going to go ahead and merge this and open an new issue to track adding flipped to the examples.

[jackbdu]

@ziyuan-linn Thank you for adding this alias! This works perfectly fine for faceMesh and handPose, but neither { flipped: true } nor { flipHorizontal: true } works for blazePose bodyPose. Can you take a look what might be the issue?

[ziyuan-linn]

@jackbdu Thank you for letting me know about this issue!

Looks like the filpHorizontal feature for pose-detection was never implemented by TFJS.

I am happy to implement this on ml5.js's end and update you.

[jackbdu]

@ziyuan-linn Thank you! That would be great, especially considering it is supported in all other models!

In the repo you linked to, I found that mediapipe BlazePose supports flipHorizontal, but it is the only one that does. I wonder if the tensorflow team would be willing to implement it as well.

[ziyuan-linn]

@jackbdu Thank you for the information!

I made PR #174 to address this issue, along with some other bugs I found in the process 😂. Please feel free to give any suggestions.

Reaching out to the TFJS team might also be a good idea!