Visible-infrared person re-identification (VI Re-ID) is designed to match person images of the same identity from visible and infrared cameras. Transformer structures have been successfully applied in the field of VI Re-ID. However, previous Transformer-based methods were mainly designed to capture global content information in a single modality, and could not simultaneously perceive semantic information between two modalities from a global perspective. To solve this problem, we propose a novel framework named the cross-modality interaction Transformer (CMIT). It has strong abilities in modeling spatial and sequential features that can capture dependencies between long-range features, and explicitly improves the discriminativeness of features by exchanging information across modalities, thus contributing to obtaining modality-invariant representations. Specifically, CMIT utilizes a cross-modality attention mechanism to enrich the feature representations of each patch token by interacting with the patch tokens of the other modality, and aggregates local features of the CNN structure and global information of the Transformer structure to mine feature saliency representation. Furthermore, the modality-discriminative (MD) loss function is proposed to learn potential consistency between modalities to encourage intra-modality compactness within class and inter-modality separation between classes. Extensive experiments on two benchmarks demonstrate that our approach outperforms state-of-the-art methods.

Visible-infrared person re-identification (VI-ReID) aims to match person images between the visible and near-infrared modalities. Previous VI-ReID methods are based on holistic pedestrian images and achieve excellent performance. However, in real-world scenarios, images captured by visible and near-infrared cameras usually contain occlusions. The performance of these methods degrades significantly due to the loss of information of discriminative features from the occlusion of the images. We define visible-infrared person re-identification in this occlusion scene as Occluded VI-ReID, where only partial content information of pedestrian images can be used to match images of different modalities from different cameras. In this paper, we propose a matching framework for occlusion scenes, which contains a local feature enhance module (LFEM) and a modality information fusion module (MIFM). LFEM adopts Transformer to learn features of each modality, and adjusts the importance of patches to enhance the representation ability of local features of the non-occluded areas. MIFM utilizes a co-attention mechanism to infer the correlation between each image for reducing the difference between modalities. We construct two occluded VI-ReID datasets, namely Occluded-SYSU-MM01 and Occluded-RegDB datasets. Our approach outperforms existing state-of-the-art methods on two occlusion datasets, while remains top performance on two holistic datasets.

Due to changes in illumination, adverse weather conditions, and interference from signs similar to real traffic signs, the false detection of traffic signs is possible. Nevertheless, in order to improve the detection effect of small targets, baseline SSD (single shot multibox detector) adopts a multi-scale feature detection method to improve the detection effect to some extent. The detection effect of small targets is improved, but the number of calculations needed for the baseline SSD network is large. To this end, we propose a lightweight SSD network algorithm. This method uses some 1 × 1 convolution kernels to replace some of the 3 × 3 convolution kernels in the baseline network and deletes some convolutional layers to reduce the calculation load of the baseline SSD network. Then the color detection algorithm based on the phase difference method and the connected component calculation are used to further filter the detection results, and finally, the data enhancement strategy based on the image appearance transformation is used to improve the balance of the dataset. The experimental results show that the proposed method is 3% more accurate than the baseline SSD network, and more importantly, the detection speed is also increased by 1.2 times.

Video-based visible-infrared person re-identification (VVI-ReID) aims to match the identity of a person captured in video sequences from both visible and infrared cameras. The VVI-ReID task requires considering both the spatial relationship between body parts within each frame and the temporal change of appearance between successive frames. Existing VVI Re-ID methods employ Convolutional Neural Networks to extract local spatial features and Long Short-Term Memory to form temporal associations. However, these methods can not effectively capture the global spatial feature and the long-range temporal dependencies in ultra-long sequences. In this paper, we propose a Cross-modality Spatial-temporal Transformer (CST) including a Cross-frame Tube Transformer Module (CTTM) and a Multi-frame Transformer Fusion Module (MTFM) to address these challenges. Firstly, CTTM tokenizes a video clip into multiple 3D tubes, each encapsulating local spatial-temporal information of pedestrians, and then obtains global spatial-temporal representations by establishing the relationship between tubes. Secondly, we design MTFM to exchange information between multiple frames using message tokens, thus modeling the long-range temporal dependencies of features of pedestrians. In addition, to prevent the potential representation collapse caused by triplet-based loss functions, we propose a diversity-consistency (DC) loss function to preserve the diversity and consistency of cross-modality feature representations by imposing variance, invariance, and covariance constraints in feature representations. Extensive benchmark experiments demonstrate that our approach outperforms the state-of-the-art methods with large margins.