Unsupervised Learning of Intrinsic Semantics With Diffusion Model for Person Re-Identification

Unsupervised person re-identification (Re-ID) aims to learn semantic representations for person retrieval without using identity labels. Most existing methods generate fine-grained patch features to reduce noise in global feature clustering. However, these methods often compromise the discriminative semantic structure and overlook the semantic consistency between the patch and global features. To address these problems, we propose a Person Intrinsic Semantic Learning (PISL) framework with diffusion model for unsupervised person Re-ID. First, we design the Spatial Diffusion Model (SDM), which performs a denoising diffusion process from noisy spatial transformer parameters to semantic parameters, enabling the sampling of patches with intrinsic semantic structure. Second, we propose the Semantic Controlled Diffusion (SCD) loss to guide the denoising direction of the diffusion model, facilitating the generation of semantic patches. Third, we propose the Patch Semantic Consistency (PSC) loss to capture semantic consistency between the patch and global features, refining the pseudo-labels of global features. Comprehensive experiments on three challenging datasets show that our method surpasses current unsupervised Re-ID methods. The source code will be publicly available at https://github.com/taoxuefong/Diffusion-reid