tchigher / contrastive-unpaired-translation

Contrastive unpaired image-to-image translation, faster and lighter training than cyclegan (ECCV 2020, in PyTorch)

Contrastive Unpaired Translation (CUT)

video | website | paper

We provide our PyTorch implementation of unpaired image-to-image translation based on patchwise contrastive learning and adversarial learning. No hand-crafted loss and inverse network is used. Compared to CycleGAN, our model training is faster and less memory-intensive. In addition, our method can be extended to single image training, where each “domain” is only a single image.

Contrastive Learning for Unpaired Image-to-Image Translation
Taesung Park, Alexei A. Efros, Richard Zhang, Jun-Yan Zhu
UC Berkeley and Adobe Research
In ECCV 2020

Pseudo code

import torch
cross_entropy_loss = torch.nn.CrossEntropyLoss()

# Input: f_q (BxCxS) and sampled features from H(G_enc(x))
# Input: f_k (BxCxS) are sampled features from H(G_enc(G(x))
# Input: tau is the temperature used in PatchNCE loss.
# Output: PatchNCE loss
def PatchNCELoss(f_q, f_k, tau=0.07):
    # batch size, channel size, and number of sample locations
    B, C, S = f_q.shape

    # calculate v * v+: BxSx1
    l_pos = (f_k * f_q).sum(dim=1)[:, :, None]

    # calculate v * v-: BxSxS
    l_neg = torch.bmm(f_q.transpose(1, 2), f_k)

    # The diagonal entries are not negatives. Remove them.
    identity_matrix = torch.eye(S)[None, :, :]
    l_neg.masked_fill_(identity_matrix, -float('inf'))

    # calculate logits: (B)x(S)x(S+1)
    logits = torch.cat((l_pos, l_neg), dim=2) / tau

    # return PatchNCE loss
    predictions = logits.flatten(0, 1)
    targets = torch.zeros(B * S, dtype=torch.long)
    return cross_entropy_loss(predictions, targets)

Example Results

Unpaired Image-to-Image Translation

Single Image Unpaired Translation

Russian Blue Cat to Grumpy Cat

Parisian Street to Burano's painted houses

Prerequisites

• Linux or macOS
• Python 3
• CPU or NVIDIA GPU + CUDA CuDNN

Getting started

• Clone this repo:

git clone https://github.com/taesungp/contrastive-unpaired-translation CUT
cd CUT

• Install PyTorch 1.1 and other dependencies (e.g., torchvision, visdom, dominate, gputil).

  For pip users, please type the command pip install -r requirements.txt.

  For Conda users, you can create a new Conda environment using conda env create -f environment.yml.

CUT and FastCUT Training and Test

• Download the grumpifycat dataset (Fig 8 of the paper. Russian Blue -> Grumpy Cats)

bash ./datasets/download_cut_dataset.sh grumpifycat

The dataset is downloaded and unzipped at ./datasets/grumpifycat/.

• To view training results and loss plots, run python -m visdom.server and click the URL http://localhost:8097.

• Train the CUT model:

python train.py --dataroot ./datasets/grumpifycat --name grumpycat_CUT --CUT_mode CUT

Or train the FastCUT model

python train.py --dataroot ./datasets/grumpifycat --name grumpycat_FastCUT --CUT_mode FastCUT

The checkpoints will be stored at ./checkpoints/grumpycat_*/web.

• Test the CUT model:

python test.py --dataroot ./datasets/grumpifycat --name grumpycat_CUT --CUT_mode CUT --phase train

The test results will be saved to a html file here: ./results/grumpifycat/latest_test/index.html.

CUT, FastCUT, and CycleGAN

CUT is trained with the identity preservation loss and with lambda_NCE=1, while FastCUT is trained without the identity loss but with higher lambda_NCE=10.0. Compared to CycleGAN, CUT learns to perform more powerful distribution matching, while FastCUT is designed as a lighter (half the GPU memory, can fit a larger image), and faster (twice faster to train) alternative to CycleGAN. Please refer to the paper for more details.

In the above figure, we measure the percentage of pixels belonging to the horse/zebra bodies, using a pre-trained semantic segmentation model. We find a distribution mismatch between sizes of horses and zebras images -- zebras usually appear larger (36.8% vs. 17.9%). Our full method CUT has the flexibility to enlarge the horses, as a means of better matching of the training statistics than CycleGAN. FastCUT behaves more conservatively like CycleGAN.

Training using our launcher scripts

Please see experiments/grumpifycat_launcher.py that generates the above command line arguments. The launcher scripts are useful for configuring rather complicated command-line arguments of training and testing.

Using the launcher, the command below generates the training command of CUT and FastCUT.

python -m experiments grumpifycat train 0   # CUT
python -m experiments grumpifycat train 1   # FastCUT

To test using the launcher,

python -m experiments grumpifycat test 0   # CUT
python -m experiments grumpifycat test 1   # FastCUT

Possible commands are run, run_test, launch, close, and so on. Please see experiments/__main__.py for all commands

Apply a pre-trained CUT model and evaluate

The tutorial for using pretrained models will be released soon.

SinCUT Single Image Unpaired Training

The tutorial for the Single-Image Translation will be released soon.

Citation

If you use this code for your research, please cite our paper.

@inproceedings{park2020cut,
  title={Contrastive Learning for Unpaired Image-to-Image Translation},
  author={Taesung Park and Alexei A. Efros and Richard Zhang and Jun-Yan Zhu},
  booktitle={European Conference on Computer Vision},
  year={2020}
}

If you use the original pix2pix and CycleGAN model included in this repo, please cite the following papers

@inproceedings{CycleGAN2017,
  title={Unpaired Image-to-Image Translation using Cycle-Consistent Adversarial Networkss},
  author={Zhu, Jun-Yan and Park, Taesung and Isola, Phillip and Efros, Alexei A},
  booktitle={Computer Vision (ICCV), 2017 IEEE International Conference on},
  year={2017}
}


@inproceedings{isola2017image,
  title={Image-to-Image Translation with Conditional Adversarial Networks},
  author={Isola, Phillip and Zhu, Jun-Yan and Zhou, Tinghui and Efros, Alexei A},
  booktitle={Computer Vision and Pattern Recognition (CVPR), 2017 IEEE Conference on},
  year={2017}
}

Acknowledgments

We thank Allan Jabri and Phillip Isola for helpful discussion and feedback. Our code is developed based on pytorch-CycleGAN-and-pix2pix. We also thank pytorch-fid for FID computation, drn for mIoU computation, and stylegan2-pytorch for the PyTorch implementation of StyleGAN2 used in our single-image translation setting.