Request to Add Pixel Attack and Threshold Attack

[shashankkotyan]

I would like to add an implementation of Few Pixel Attack (https://arxiv.org/pdf/1906.06026.pdf) which is a generalisation of One Pixel Attack (https://arxiv.org/pdf/1710.08864.pdf) and Threshold Attack (https://arxiv.org/pdf/1906.06026.pdf).

• Added Implementation of Pixel Attack and Threshold Attack.
• Updated init file.
• Requires pycma (https://github.com/CMA-ES/pycma) library.

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

:memo: Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here with @googlebot I signed it! and we'll verify it.

---

What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

ℹ️ Googlers: Go here for more info.

[shashankkotyan]

@googlebot I signed it!

[googlebot]

CLAs look good, thanks!

ℹ️ Googlers: Go here for more info.

[jonasguan]

Hi @shashankkotyan , thanks for the PR. Unfortunately we're undergoing some major updates and have dropped support for the current version using TF1 in favor for TF2, PyTorch and Jax, so I'll have to close this for now. However, if you would like to open a new PR for the upcoming new library version, we'd much welcome your contribution.

A few comments/questions, in case you would like to resubmit: Is the paper for the Few Pixel Attack peer-reviewed anywhere? Is it possible to implement (without too much trouble) without adding the pycma library as a dependency? Also, we'd prefer it if you can fill in the TODO comments, since it's usually best to have the developer who wrote the code add the comments to ensure correctness.