Contrastive-Generative-Contrastive: Neutralize Subjectivity in Sketch Re-Identification

Sketch-based person re-identification (Sketch re-ID) aims to match pedestrian figures in hand-drawn sketches with their corresponding RGB photos. This technique allows for person retrieval or tracking in surveillance systems when the target person’s RGB photo is not available. While previous research predominantly focused on bridging the modality gap between sketches and RGB photos, the influence of the inherent subjectivity in hand-drawn sketches on re-ID performance remains under-explored. This subjectivity, originating from the artist’s unique style, perceptions, and interpretations, introduces inaccuracies in depicting pedestrian appearances, thereby posing additional challenges such as feature distortion and stylistic variation. This paper introduces a Contrastive-Generative-Contrastive (CGC) framework for subjective style-insensitive re-ID. The framework employs a generative model optimized through self-supervision by contrasting positive and negative pairs of pedestrian sketches and RGB photos. In this manner, it simulates an additional artist specializing in transforming original sketches from various subjective styles into uniform ones. Besides, a simple yet effective weighted contrastive learning loss is proposed to further enhance the model’s focus on pedestrian ID-relevant features. Experimental results demonstrate that the proposed method significantly reduces the influence of subjectivity in feature extraction, achieving new state-of-the-art results on benchmark datasets.