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Propagate Yourself: Exploring Pixel-Level Consistency for Unsupervised Visual Representation Learning

19 Nov 2020CVPR 2021 1arXiv:2011.10043archive 2025-07-28

Zhenda Xie, Yutong Lin, Zheng Zhang, Yue Cao, Stephen Lin, Han Hu

Contrastive learning methods for unsupervised visual representation learning have reached remarkable levels of transfer performance. We argue that the power of contrastive learning has yet to be fully unleashed, as current methods are trained only on instance-level pretext tasks, leading to representations that may be sub-optimal for downstream tasks requiring dense pixel predictions. In this paper, we introduce pixel-level pretext tasks for learning dense feature representations. The first task directly applies contrastive learning at the pixel level. We additionally propose a pixel-to-propagation consistency task that produces better results, even surpassing the state-of-the-art approaches by a large margin. Specifically, it achieves 60.2 AP, 41.4 / 40.5 mAP and 77.2 mIoU when transferred to Pascal VOC object detection (C4), COCO object detection (FPN / C4) and Cityscapes semantic segmentation using a ResNet-50 backbone network, which are 2.6 AP, 0.8 / 1.0 mAP and 1.0 mIoU better than the previous best methods built on instance-level contrastive learning. Moreover, the pixel-level pretext tasks are found to be effective for pre-training not only regular backbone networks but also head networks used for dense downstream tasks, and are complementary to instance-level contrastive methods. These results demonstrate the strong potential of defining pretext tasks at the pixel level, and suggest a new path forward in unsupervised visual representation learning. Code is available at \url{https://github.com/zdaxie/PixPro}.

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zdaxie/PixPro officialmentioned in papermentioned on GitHubpytorch report
PaperCodeReview/PixPro-TF mentioned on GitHubtf report
conradry/pixpro-with-weights mentioned on GitHubpytorch report
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grid_distances conradry/pixpro-with-weights/pixpro/model.py community (archive-listed) ran · fixture could not drive it fingerprinted MIT (permissive) · f66fbbbeae521681 · report
rand_true lucidrains/pixel-level-contrastive-learning/pixel_level_contrastive_learning/pixel_level_contrastive_learning.py community (archive-listed) ran · violated contract MIT (permissive) · 533e2e35b9373e76 · report
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Contrastive LearningObject DetectionRepresentation LearningSemantic Segmentationobject-detection

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Contrastive Learning

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