Collecting labeled data for the task of semantic segmentation is expensive and time-consuming, as it requires dense pixel-level annotations. While recent Convolutional Neural Network (CNN) based semantic segmentation approaches have achieved impressive results by using large amounts of labeled training data, their performance drops significantly as the amount of labeled data decreases. This happens because deep CNNs trained with the de facto cross-entropy loss can easily overfit to small amounts of labeled data. To address this issue, we propose a simple and effective contrastive learning-based training strategy in which we first pretrain the network using a pixel-wise class label-based contrastive loss, and then fine-tune it using the cross-entropy loss. This approach increases intra-class compactness and inter-class separability thereby resulting in a better pixel classifier. We demonstrate the effectiveness of the proposed training strategy in both fully-supervised and semi-supervised settings using the Cityscapes and PASCAL VOC 2012 segmentation datasets. Our results show that pretraining with label-based contrastive loss results in large performance gains (more than 20% absolute improvement in some settings) when the amount of labeled data is limited.

本文提出了一种基于对比度学习的语义分割训练策略，使用像素级和标签基础对比损失的方法，能够在减少标记数据的情况下提高性能，并通过 Cityscapes 和 PASCAL VOC 2012 数据集的实验证明了该方法的有效性。

对比学习用于标签少的语义分割