Towards Cross-Granularity Few-Shot Learning: Coarse-to-Fine Pseudo-Labeling with Visual-Semantic Meta-Embedding

Meta-learning has recently emerged as a promising technique to address the challenge of few-shot learning. However, most existing meta-learning algorithms require fine-grained supervision, thereby involving prohibitive annotation cost. In this paper, we present a new problem named inexactly-supervised meta-learning to alleviate such limitation, focusing on tackling few-shot classification tasks with only coarse-grained supervision. Accordingly, we propose a Coarse-to-Fine (C2F) pseudo-labeling process to construct pseudo-tasks from coarsely-labeled data by grouping each coarse-class into pseudo-fine-classes via similarity matching. Moreover, we develop a Bi-level Discriminative Embedding (BDE) to obtain a good image similarity measure in both visual and semantic aspects with inexact supervision. Experiments across representative benchmarks indicate that our approach shows profound advantages over baseline models.