  Given a descriptive text query, text-based person search (TBPS) aims to
retrieve the best-matched target person from an image gallery. Such a
cross-modal retrieval task is quite challenging due to significant modality
gap, fine-grained differences and insufficiency of annotated data. To better
align the two modalities, most existing works focus on introducing
sophisticated network structures and auxiliary tasks, which are complex and
hard to implement. In this paper, we propose a simple yet effective dual
Transformer model for text-based person search. By exploiting a hardness-aware
contrastive learning strategy, our model achieves state-of-the-art performance
without any special design for local feature alignment or side information.
Moreover, we propose a proximity data generation (PDG) module to automatically
produce more diverse data for cross-modal training. The PDG module first
introduces an automatic generation algorithm based on a text-to-image diffusion
model, which generates new text-image pair samples in the proximity space of
original ones. Then it combines approximate text generation and feature-level
mixup during training to further strengthen the data diversity. The PDG module
can largely guarantee the reasonability of the generated samples that are
directly used for training without any human inspection for noise rejection. It
improves the performance of our model significantly, providing a feasible
solution to the data insufficiency problem faced by such fine-grained
visual-linguistic tasks. Extensive experiments on two popular datasets of the
TBPS task (i.e., CUHK-PEDES and ICFG-PEDES) show that the proposed approach
outperforms state-of-the-art approaches evidently, e.g., improving by 3.88%,
4.02%, 2.92% in terms of Top1, Top5, Top10 on CUHK-PEDES. The codes will be
available at https://github.com/HCPLab-SYSU/PersonSearch-CTLG
