Semi-supervised Semantic Segmentation with Directional Context-aware Consistency
This work addresses the challenge of reducing annotation costs for semantic segmentation, which is crucial for applications like autonomous driving and medical imaging, though it appears incremental as it builds on existing consistency-based approaches.
The paper tackles the problem of poor generalization in semi-supervised semantic segmentation due to limited annotations by proposing a method to maintain context-aware consistency in features, resulting in state-of-the-art performance with significant improvements over existing methods.
Semantic segmentation has made tremendous progress in recent years. However, satisfying performance highly depends on a large number of pixel-level annotations. Therefore, in this paper, we focus on the semi-supervised segmentation problem where only a small set of labeled data is provided with a much larger collection of totally unlabeled images. Nevertheless, due to the limited annotations, models may overly rely on the contexts available in the training data, which causes poor generalization to the scenes unseen before. A preferred high-level representation should capture the contextual information while not losing self-awareness. Therefore, we propose to maintain the context-aware consistency between features of the same identity but with different contexts, making the representations robust to the varying environments. Moreover, we present the Directional Contrastive Loss (DC Loss) to accomplish the consistency in a pixel-to-pixel manner, only requiring the feature with lower quality to be aligned towards its counterpart. In addition, to avoid the false-negative samples and filter the uncertain positive samples, we put forward two sampling strategies. Extensive experiments show that our simple yet effective method surpasses current state-of-the-art methods by a large margin and also generalizes well with extra image-level annotations.