High-fidelity Pseudo-labels for Boosting Weakly-Supervised Segmentation

The task of image-level weakly-supervised semantic segmentation (WSSS) has gained popularity in recent years, as it reduces the vast data annotation cost for training segmentation models. The typical approach for WSSS involves training an image classification network using global average pooling (GAP) on convolutional feature maps. This enables the estimation of object locations based on class activation maps (CAMs), which identify the importance of image regions. The CAMs are then used to generate pseudo-labels, in the form of segmentation masks, to supervise a segmentation model in the absence of pixel-level ground truth. In case of the SEAM baseline, a previous work proposed to improve CAM learning in two ways: (1) Importance sampling, which is a substitute for GAP, and (2) the feature similarity loss, which utilizes a heuristic that object contours almost exclusively align with color edges in images. In this work, we propose a different probabilistic interpretation of CAMs for these techniques, rendering the likelihood more appropriate than the multinomial posterior. As a result, we propose an add-on method that can boost essentially any previous WSSS method, improving both the region similarity and contour quality of all implemented state-of-the-art baselines. This is demonstrated on a wide variety of baselines on the PASCAL VOC dataset. Experiments on the MS COCO dataset show that performance gains can also be achieved in a large-scale setting. Our code is available at https://github.com/arvijj/hfpl.