Cross-Category Subjectivity Generalization for Style-Adaptive Sketch Re-ID

Sketch-based person re-identification (re-ID) enables pedestrian retrieval using sketches. While recent methods have improved modality alignment between sketches and RGB images, the challenge of subjective style variation, where sketches exhibit diverse and unpredictable appearances, remains largely unresolved. A natural solution is to train on a diverse range of pedestrian sketches, but the high cost of large-scale pedestrian sketch collection makes this impractical. In contrast, sketches of general categories (e.g., animals, objects) exhibit diverse style variations and are accessible at a low cost, making them an intuitive and scalable alternative for enhancing style generalization in sketch re-ID. To this end, we propose Adaptive Incremental Prompt-tuning (AIP), the first approach that explores cross-category subjective style generalization for sketch re-ID. Specifically, AIP incorporates a multi-stage prompt-tuning strategy that learns a broad but shareable spectrum of sketch styles from non-pedestrian data. In addition, an input-sensitive prompt generator enables the model to adapt dynamically to unseen sketch styles. Extensive experimental results demonstrate that the performance gain is not simply due to the inclusion of additional data but stems from the effectiveness of AIP in leveraging non-pedestrian data for subjective style generalization. Our method substantially improves performance over existing approaches, setting new state-of-the-art results.