Multi-Granularity Matching Transformer for Text-Based Person Search

Text-based person search aims to retrieve the most relevant pedestrian images from an image gallery based on textual descriptions. Most existing methods rely on two separate encoders to extract the image and text features, and then elaborately design various schemes to bridge the gap between image and text modalities. However, the shallow interaction between both modalities in these methods is still insufficient to eliminate the modality gap. To address the above problem, we propose TransTPS, a transformer-based framework that enables deeper interaction between both modalities through the self-attention mechanism in transformer, effectively alleviating the modality gap. In addition, due to the small inter-class variance and large intra-class variance in image modality, we further develop two techniques to overcome these limitations. Specifically, Cross-modal Multi-Granularity Matching (CMGM) is proposed to address the problem caused by small inter-class variance and facilitate distinguishing pedestrians with similar appearance. Besides, Contrastive Loss with Weakly Positive pairs (CLWP) is introduced to mitigate the impact of large intra-class variance and contribute to the retrieval of more target images. Experiments on CUHK-PEDES and RSTPReID datasets demonstrate that our proposed framework achieves state-of-the-art performance compared to previous methods.