The official implementation of "Puzzle-CAM: Improved localization via matching partial and full features".


  • Accepted to ICIP 2021
  • Please cite our paper if the code is helpful to your research. arxiv
  title={Puzzle-CAM: Improved localization via matching partial and full features},
  author={Jo, Sanghyun and Yu, In-Jae},
  journal={arXiv preprint arXiv:2101.11253},


Weakly-supervised semantic segmentation (WSSS) is introduced to narrow the gap for semantic segmentation performance from pixel-level supervision to image-level supervision.
Most advanced approaches are based on class activation maps (CAMs) to generate pseudo-labels to train the segmentation network.
The main limitation of WSSS is that the process of generating pseudo-labels from CAMs which use an image classifier is mainly focused on the most discriminative parts of the objects.
To address this issue, we propose Puzzle-CAM, a process minimizes the differences between the features from separate patches and the whole image.
Our method consists of a puzzle module (PM) and two regularization terms to discover the most integrated region of in an object.
Without requiring extra parameters, Puzzle-CAM can activate the overall region of an object using image-level supervision.
In experiments, Puzzle-CAM outperformed previous state-of-the-art methods using the same labels for supervision on the PASCAL VOC 2012 test dataset.




  • Python 3.8, PyTorch 1.7.0, and more in requirements.txt
  • CUDA 10.1, cuDNN 7.6.5
  • 4 x Titan RTX GPUs


Install python dependencies

python3 -m pip install -r requirements.txt

Download PASCAL VOC 2012 devkit

Follow instructions in http://host.robots.ox.ac.uk/pascal/VOC/voc2012/#devkit

1. Train an image classifier for generating CAMs

CUDA_VISIBLE_DEVICES=0,1,2,3 python3 train_classification_with_puzzle.py --architecture resnest101 --re_loss_option masking --re_loss L1_Loss --alpha_schedule 0.50 --alpha 4.00 --tag [email protected]@optimal --data_dir $your_dir

2. Apply Random Walk (RW) to refine the generated CAMs

2.1. Make affinity labels to train AffinityNet.

CUDA_VISIBLE_DEVICES=0 python3 inference_classification.py --architecture resnest101 --tag [email protected]@optimal --domain train_aug --data_dir $your_dir
python3 make_affinity_labels.py --experiment_name [email protected]@[email protected]@scale=0.5,1.0,1.5,2.0 --domain train_aug --fg_threshold 0.40 --bg_threshold 0.10 --data_dir $your_dir

2.2. Train AffinityNet.

CUDA_VISIBLE_DEVICES=0 python3 train_affinitynet.py --architecture resnest101 --tag [email protected]@Puzzle --label_name [email protected]@[email protected]@scale=0.5,1.0,1.5,[email protected]_fg=0.40_bg=0.10 --data_dir $your_dir

3. Train the segmentation model using the pseudo-labels

3.1. Make segmentation labels to train segmentation model.

CUDA_VISIBLE_DEVICES=0 python3 inference_rw.py --architecture resnest101 --model_name [email protected]@Puzzle --cam_dir [email protected]@[email protected]@scale=0.5,1.0,1.5,2.0 --domain train_aug --data_dir $your_dir
python3 make_pseudo_labels.py --experiment_name [email protected]@[email protected]@[email protected][email protected] --domain train_aug --threshold 0.35 --crf_iteration 1 --data_dir $your_dir

3.2. Train segmentation model.

CUDA_VISIBLE_DEVICES=0,1,2,3 python3 train_segmentation.py --backbone resnest101 --mode fix --use_gn True --tag [email protected]@[email protected] --label_name [email protected]@[email protected]@[email protected][email protected]@crf=1 --data_dir $your_dir

4. Evaluate the models

CUDA_VISIBLE_DEVICES=0 python3 inference_segmentation.py --backbone resnest101 --mode fix --use_gn True --tag [email protected]@[email protected] --scale 0.5,1.0,1.5,2.0 --iteration 10

python3 evaluate.py --experiment_name [email protected]@[email protected]@[email protected]=0.5,1.0,1.5,[email protected]=10 --domain val --data_dir $your_dir/SegmentationClass

5. Results

Qualitative segmentation results on the PASCAL VOC 2012 validation set.
Top: original images. Middle: ground truth. Bottom: prediction of the segmentation model trained using the pseudo-labels from Puzzle-CAM.

Methods background aeroplane bicycle bird boat bottle bus car cat chair cow diningtable dog horse motorbike person pottedplant sheep sofa train tvmonitor mIoU
Puzzle-CAM with ResNeSt-101 88.9 87.1 38.7 89.2 55.8 72.8 89.8 78.9 91.3 26.8 84.4 40.3 88.9 81.9 83.1 34.0 60.1 83.6 47.3 59.6 38.8 67.7
Puzzle-CAM with ResNeSt-269 91.1 87.2 37.3 86.8 61.4 71.2 92.2 86.2 91.8 28.6 85.0 64.1 91.8 82.0 82.5 70.7 69.4 87.7 45.4 67.0 37.7 72.2