  Referring image segmentation aims to predict the foreground mask of the
object referred by a natural language sentence. Multimodal context of the
sentence is crucial to distinguish the referent from the background. Existing
methods either insufficiently or redundantly model the multimodal context. To
tackle this problem, we propose a "gather-propagate-distribute" scheme to model
multimodal context by cross-modal interaction and implement this scheme as a
novel Linguistic Structure guided Context Modeling (LSCM) module. Our LSCM
module builds a Dependency Parsing Tree suppressed Word Graph (DPT-WG) which
guides all the words to include valid multimodal context of the sentence while
excluding disturbing ones through three steps over the multimodal feature,
i.e., gathering, constrained propagation and distributing. Extensive
experiments on four benchmarks demonstrate that our method outperforms all the
previous state-of-the-arts.
