  Open-vocabulary semantic segmentation (OVS) aims to segment images of
arbitrary categories specified by class labels or captions. However, most
previous best-performing methods, whether pixel grouping methods or region
recognition methods, suffer from false matches between image features and
category labels. We attribute this to the natural gap between the textual
features and visual features. In this work, we rethink how to mitigate false
matches from the perspective of image-to-image matching and propose a novel
relation-aware intra-modal matching (RIM) framework for OVS based on visual
foundation models. RIM achieves robust region classification by firstly
constructing diverse image-modal reference features and then matching them with
region features based on relation-aware ranking distribution. The proposed RIM
enjoys several merits. First, the intra-modal reference features are better
aligned, circumventing potential ambiguities that may arise in cross-modal
matching. Second, the ranking-based matching process harnesses the structure
information implicit in the inter-class relationships, making it more robust
than comparing individually. Extensive experiments on three benchmarks
demonstrate that RIM outperforms previous state-of-the-art methods by large
margins, obtaining a lead of more than 10% in mIoU on PASCAL VOC benchmark.
