Composed Image Retrieval (CIR) enables image retrieval by combining multiple query modalities, but existing benchmarks predominantly focus on general-domain imagery and rely on reference images with short textual modifications. As a result, they provide limited support for retrieval scenarios that require fine-grained semantic reasoning, structured visual understanding, and domain-specific knowledge. In this work, we introduce CIRThan, a sketch+text composed image retrieval dataset for Thangka imagery, a culturally grounded and knowledge-specific visual domain characterized by complex structures, dense symbolic elements, and domain-dependent semantic conventions. CIRThan contains 2,287 high-quality Thangka images, each paired with a human-drawn sketch and hierarchical textual descriptions at three semantic levels, enabling composed queries that jointly express structural intent and multi-level semantic specification. We provide standardized data splits, comprehensive dataset analysis, and benchmark evaluations of representative supervised and zero-shot CIR methods. Experimental results reveal that existing CIR approaches, largely developed for general-domain imagery, struggle to effectively align sketch-based abstractions and hierarchical textual semantics with fine-grained Thangka images, particularly without in-domain supervision. We believe CIRThan offers a valuable benchmark for advancing sketch+text CIR, hierarchical semantic modeling, and multimodal retrieval in cultural heritage and other knowledge-specific visual domains. The dataset is publicly available at https://github.com/jinyuxu-whut/CIRThan.

Composed Image Retrieval (CIR) aims to retrieve a target image from a query composed of a reference image and modification text. Recent training-free zero-shot methods often employ Multimodal Large Language Models (MLLMs) with Chain-of-Thought (CoT) to compose a target image description for retrieval. However, due to the fuzzy matching nature of ZS-CIR, the generated description is prone to semantic bias relative to the target image. We propose SDR-CIR, a training-free Semantic Debias Ranking method based on CoT reasoning. First, Selective CoT guides the MLLM to extract visual content relevant to the modification text during image understanding, thereby reducing visual noise at the source. We then introduce a Semantic Debias Ranking with two steps, Anchor and Debias, to mitigate semantic bias. In the Anchor step, we fuse reference image features with target description features to reinforce useful semantics and supplement omitted cues. In the Debias step, we explicitly model the visual semantic contribution of the reference image to the description and incorporate it into the similarity score as a penalty term. By supplementing omitted cues while suppressing redundancy, SDR-CIR mitigates semantic bias and improves retrieval performance. Experiments on three standard CIR benchmarks show that SDR-CIR achieves state-of-the-art results among one-stage methods while maintaining high efficiency. The code is publicly available at https://github.com/suny105/SDR-CIR.

Due to the remarkable performance of multi-modal large language models (MLLMs) in multi-modal capabilities, multi-modal in-context learning (M-ICL) has garnered widespread attention for fast adapting MLLMs to downstream tasks. However, the vulnerability of M-ICL to attacks remains largely unexplored. In this work, we take the first step to explore the backdoor vulnerability of M-ICL, which allows the adversary only to manipulate the multi-modal demonstration examples to mislead the victim model. We propose a multi-modal backdoor strategy on M-ICL via cross-modal concept mis-matching under black-box attack setting. Extensive experimental results demonstrate that our attacks exhibit high attack effectiveness while preserving the normal functionality of the victim model. Moreover, we further conduct experiments to prove our attacks are robust against backdoor defenses and still remain effective in various real-world conditions.

Thangka art, part of the UNESCO Intangible Cultural Heritage of Humanity, is visually characterized by complex junctions and intricate corners, demand high-fidelity vectorization to preserve its structural integrity and smooth curvilinear aesthetics. Conventional line art vectorization algorithms applied to Thangka element line art face challenges: (1) hard to fit complex junctions that leads to spurious spikes and discontinuous strokes; and (2) unnatural distortions in long curves due to insufficient smoothness constraints. To address these challenges, we propose a skeleton-guided vectorization framework to optimize the topology of vectorized Thangka element line art, and a multilayer perceptual loss as a smoothness regulation to improve curve continuity. Experimental results on manually annotated Thangka element line art dataset demonstrate that our method surpasses state-of-the-art approaches in preserving topological integrity and achieving visual smoothness, offering a robust foundation for digitizing cultural heritage artworks with complex topologies and similar aesthetic requirements.

With the widespread adoption of deep learning in image recognition, backdoor attacks have emerged as a significant security threat, drawing increasing attention from the research community. Traditional backdoor attacks are often limited to the digital domain, while few existing physical-world attacks suffer from a lack of stealthiness. In this paper, inspired by the natural defocus blur commonly caused by camera optics in real-world environments, we propose a physically-aware backdoor attack method called DBBA based on the defocus blur phenomenon. By leveraging Gaussian blur to simulate this natural phenomenon, the proposed method enhances both the stealthiness and plausibility of the trigger. To further optimize the attack effectiveness while maintaining stealthiness, we introduce a Particle Swarm Optimization (PSO) algorithm to automatically search for the optimal Gaussian blur parameters that best simulate the defocus phenomenon. We conduct extensive experiments on multiple mainstream image classification datasets and across various model architectures. Experimental results demonstrate that the proposed defocus-blur based trigger achieves a high attack effectiveness with minimal degradation in the classification accuracy of the model. In addition, evaluations against representative defense techniques reveal that the proposed method exhibits strong stealthiness and robustness.

Text-to-Image person re-identification (TIReID) aims to retrieve pedestrian images from a gallery based on textual descriptions, thus bridging vision and language modalities for practical retrieval scenarios. Despite recent advances leveraging various cross-modal alignment strategies, existing methods typically assume all image-text pairs in training datasets are correctly matched, overlooking the pervasive Noisy Correspondence (NC) problem—erroneous image-text associations that degrade model robustness. Prior approaches either lack noise identification mechanisms or rely on direct filtering of detected noisy samples, which only partially mitigates the adverse effects of noise and cannot fully prevent overfitting to incorrect correspondences during training. Addressing this challenge, we propose Robust Dual Embedding Contrastive Learning (RDECL), which consists of two main components: 1) A Dual-View Cumulative Trust Division (DCTD) progressively constructs a high-confidence clean sample repository via adaptive sample selection, ensuring reliable image-text correspondence learning under uncertain noise detection.2) A Robust Generalized Contrastive Loss (RGCL) further enhances robustness by leveraging all negative samples and maximizing the loss distribution discrepancy between clean and noisy samples, thereby suppressing overfitting to noisy labels. We conduct extensive experiments on three public benchmark datasets, namely CUHK-PEDES, ICFG-PEDES, and RSTPReID, to evaluate the performance and robustness of our RDECL.

Thangka cultural elements detection aims to locate and identify instances in Thangka. However, as a unique form of pictorial art, Thangka exhibits distinct spatial structures that deviate significantly from general images in scale and density. Therefore, it is challenging for most state-of-the-art detectors designed for natural scenes to handle Thangka cultural elements detection effectively. To overcome this issue, we propose a multi-scale and dense object detector referred as MDDet. It embeds a multi-scale receptive field fusion module (MRF) that enlarges the receptive field while capturing the spatial and channel relationships at different scales, which significantly enriches the multi-scale features extracted from the backbone. In addition, we introduce a threshold-slicing aided hyper inference (T-SAHI) scheme, which adaptively slices images in dense scenarios to aid with dense object detection in the test time. We thoroughly evaluate our method, and MDDet outperforms the prior art by a clear margin on the Thangka dataset, achieving an absolute improvement of 1.9% in average precision (AP). For the challenging medium and small objects in Thangka, MDDet obtains wide margins of 12% and 3.7% in accuracy improvement, respectively. It also shows strong generalization ability when evaluated on general scenarios, e.g., Pascal VOC 2007 and MS COCO, validating the role of MDDet in object detection.

Person re-identification (re-id) has received ever-increasing research focus, because of its important role in video surveillance applications. This paper addresses the re-id problem between visible images of color cameras and infrared images of infrared cameras, which is significant in case that the appearance information is insufficient in poor illumination conditions. In this field, there are two key challenges, i.e., the difficulty to locate the discriminative information to re-identify the same person between visible and infrared images, and the difficulty to learn a robust metric for such large-scale cross-modality retrieval. In this paper, we propose a novel human body parts assistance network (BANet) to tackle the two challenges above. BANet mainly focuses on extracting discriminative information and learning robust features by leveraging the human body part cues. Extensive experiments demonstrate that the proposed approach outperforms the baseline and the state-of-the-art methods.