Semi-supervised learning (SSL) has attracted much attention in the field of medical image segmentation, which enables to alleviate the heavy burden of labelling pixel-wise annotation by extracting knowledge from unlabeled data. The existing methods basically benefit from the success of convolutional neural networks (CNNs) by keeping consistency of the predictions under small perturbations imposed on the networks or inputs. Two main concerns arise when learning such a paradigm: (1) CNNs tend to retain discriminative local features, neglecting global dependency and thus leading to inaccurate localization; (2) CNNs omit reliable feature-level and pixel-level information, resulting in sketchy pseudo-labels, especially around the confusing boundary. In this paper, we revisit the model of semi-supervised learning and develop a novel CNN-Transformer learning framework that allows for effective segmentation of medical images by producing complementary and reliable features and pseudo-label with bi-level uncertainty. Motivated by the uncertainty estimation to gain insight on feature discrimination, we explore the statistical and geometrical properties of features on network optimization and thus launching an alignment method in a more accurate and stable way. We attach equal significance to pixel-level uncertainty estimation for alleviating the influence of unreliable pseudo-labels in the training progress and advocating the reliability of predictions. Experimental results show that our method significantly surpasses existing semi-supervised approaches on two public medical image segmentation datasets.
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Video Question Answering (VideoQA) aims to comprehend intricate relationships, actions, and events within video content, as well as the inherent links between objects and scenes, to answer text-based questions accurately. Transferring knowledge from the cross-modal pre-trained model CLIP is a natural approach, but its dual-tower structure hinders fine-grained modality interaction, posing challenges for direct application to VideoQA tasks. To address this issue, we introduce a Language-Guided Visual Aggregation (LGVA) network. It employs CLIP as an effective feature extractor to obtain language-aligned visual features with different granularities and avoids resource-intensive video pre-training. The LGVA network progressively aggregates visual information in a bottom-up manner, focusing on both regional and temporal levels, and ultimately facilitating accurate answer prediction. More specifically, it employs local cross-attention to combine pre-extracted question tokens and region embeddings, pinpointing the object of interest in the question. Then, graph attention is utilized to aggregate regions at the frame level and integrate additional captions for enhanced detail. Following this, global cross-attention is used to merge sentence and frame-level embeddings, identifying the video segment relevant to the question. Ultimately, contrastive learning is applied to optimize the similarities between aggregated visual and answer embeddings, unifying upstream and downstream tasks. Our method conserves resources by avoiding large-scale video pre-training and simultaneously demonstrates commendable performance on the NExT-QA, MSVD-QA, MSRVTT-QA, TGIF-QA, and ActivityNet-QA datasets, even outperforming some end-to-end trained models. Our code is available at https://github.com/ecoxial2007/LGVA_VideoQA.
Synthesizing vivid human portraits is a research hot spot in image generation with a wide scope of applications. In addition to fidelity, generation controllability is another key factor that has long plagued its development. To address this issue, existing solutions usually adopt either textual or visual conditions for the target face synthesis, e.g., descriptions or segmentation masks, which still cannot fully control the generation due to the intrinsic shortages of each condition. In this paper, we propose to make use of both types of prior information to facilitate controllable face generation. In particular, we hope to produce coarse-grained information about faces based on the segmentation masks, such as face shapes and poses, and the text description is used to render detailed face attributes, e.g., face color, makeup and gender. More importantly, we hope that the generation can be easily controlled via interactively editing both types of information, making face generation more applicable to real-world applications. To accomplish this target, we propose a novel face generation model termed PixelFace+. In PixelFace+, both the text and mask are encoded as pixel-wise priors, based on which the pixel synthesis process is conducted to produce the expected portraits. Meanwhile, the loss objectives are also carefully designed to make sure that the generated faces are semantically aligned with both text and mask inputs. To validate the proposed PixelFace+, we conducted a comprehensive set of experiments on the widely recognized benchmark called MMCelebA. We not only quantitatively compare PixelFace+ with a bunch of newly proposed Text-to-Face(T2F) generation methods, but also give plenty of qualitative analyses. The experimental results demonstrate that PixelFace+ not only outperforms existing generation methods in both image quality and conditional matching but also shows a much superior controllability of face generation. More importantly, PixelFace+ presents a convenient and interactive way of face generation and manipulation via editing the text and mask inputs. Our SOURCE CODE and DEMO are given in our supplementary materials.
Moment Localization with Natural Language (MLNL) aims to locate the target moment from an untrimmed video by a linguistic query. Recent works reveal the severe data bias problem in MLNL and point out that the multi-modal content may not be understood by fitting the timestamp distribution. In this paper, we study the data biases on the intrinsic and extrinsic aspects: the former is mainly caused by the ambiguity of the moment boundary and the information imbalance between input and output; The latter results from the long-tail distribution of moments in MLNL datasets. To alleviate this, we propose a hybrid multi-modal debiasing network with temporal consistency constraint for MLNL. Specifically, we first design the multi-temporal Transformer to mitigate the ambiguity of boundary by integrating frame-wise features into segment-wise and dynamically matching with moment boundaries. Then, we introduce the temporal consistency constraint that highlights the action information in complex moment content to overcome the intrinsic bias from information imbalance.Furthermore, we design the hybrid linguistic activating module with external knowledge to relieve the extrinsic bias, which introduces a prior guidance to focus the discriminative information from the tail samples. Extensive experiments on three public datasets demonstrate that our model outperforms the existing methods.
Recent advances in visual-language models have shown remarkable zero-shot text-image matching ability that is transferable to downstream tasks such as object detection and segmentation. Adapting these models for object counting, however, remains a formidable challenge. In this study, we first investigate transferring vision-language models (VLMs) for class-agnostic object counting. Specifically, we propose CLIP-Count, the first end-to-end pipeline that estimates density maps for open-vocabulary objects with text guidance in a zero-shot manner. To align the text embedding with dense visual features, we introduce a patch-text contrastive loss that guides the model to learn informative patch-level visual representations for dense prediction. Moreover, we design a hierarchical patch-text interaction module to propagate semantic information across different resolution levels of visual features. Benefiting from the full exploitation of the rich image-text alignment knowledge of pretrained VLMs, our method effectively generates high-quality density maps for objects-of-interest. Extensive experiments on FSC-147, CARPK, and ShanghaiTech crowd counting datasets demonstrate state-of-the-art accuracy and generalizability of the proposed method. Code is available: https://github.com/songrise/CLIP-Count. https://github.com/songrise/CLIP-Count.
Infrared and visible image fusion has gradually proved to be a vital fork in the field of multi-modality imaging technologies. In recent developments, researchers not only focus on the quality of fused images but also evaluate their performance in downstream tasks. Nevertheless, the majority of methods seldom put their eyes on mutual learning from different modalities, resulting in fused images lacking significant details and textures. To overcome this issue, we propose an interactive graph neural network (GNN)-based architecture between cross modality for fusion, called IGNet. Specifically, we first apply a multi-scale extractor to achieve shallow features, which are employed as the necessary input to build graph structures. Then, the graph interaction module can construct the extracted intermediate features of the infrared/visible branch into graph structures. Meanwhile, the graph structures of two branches interact for cross-modality and semantic learning, so that fused images can maintain the important feature expressions and enhance the performance of downstream tasks. Besides, the proposed leader nodes can improve information propagation in the same modality. Finally, we merge all graph features to get the fusion result. Extensive experiments on different datasets (i.e. TNO, MFNet, and M3FD) demonstrate that our IGNet can generate visually appealing fused images while scoring averagely 2.59% mAP@.5 and 7.77% mIoU higher in detection and segmentation than the compared state-of-the-art methods. The source code of the proposed IGNet can be available at https://github.com/lok-18/IGNet.
Most previous approaches for analyzing food images have relied on extensively annotated datasets, resulting in significant human labeling expenses due to the varied and intricate nature of such images. Inspired by the effectiveness of contrastive self-supervised methods in utilizing unlabelled data, weiqing explore leveraging these techniques on unlabelled food images. In contrastive self-supervised methods, two views are randomly generated from an image by data augmentations. However, regarding food images, the two views tend to contain similar informative contents, causing large mutual information, which impedes the efficacy of contrastive self-supervised learning. To address this problem, we propose Feature Suppressed Contrast (FeaSC) to reduce mutual information between views. As the similar contents of the two views are salient or highly responsive in the feature map, the proposed FeaSC uses a response-aware scheme to localize salient features in an unsupervised manner. By suppressing some salient features in one view while leaving another contrast view unchanged, the mutual information between the two views is reduced, thereby enhancing the effectiveness of contrast learning for self-supervised food pre-training. As a plug-and-play module, the proposed method consistently improves BYOL and SimSiam by 1.70% ~ 6.69% classification accuracy on four publicly available food recognition datasets. Superior results have also been achieved on downstream segmentation tasks, demonstrating the effectiveness of the proposed method.
Given a descriptive language query, Video Moment Retrieval (VMR) aims to seek the corresponding semantic-consistent moment clip in the video, which is represented as a pair of the start and end timestamps. Although current methods have achieved satisfying performance, training these models heavily relies on the fully-annotated VMR datasets. Nonetheless, precise video temporal annotations are extremely labor-intensive and ambiguous due to the diverse preferences of different annotators. Although there are several works trying to explore weakly supervised VMR tasks with scattered annotated frames as labels, there is still much room to improve in terms of accuracy. Therefore, we design a new setting of VMR where users can easily point to small segments of non-controversy video moments and our proposed method can automatically fill in the remaining parts based on the video and query semantics. To support this, we propose a new framework named Video Moment Retrieval via Iterative Learning (VMRIL). It treats the partial temporal region as the seed, then expands the pseudo label by iterative training. In order to restrict the expansion with reasonable boundaries, we utilize a pretrained video action localization model to provide coarse guidance of potential video segments. Compared with other VMR methods, our VMRIL achieves a trade-off between satisfying performance and annotation efficiency. Experimental results show that our proposed method can achieve the SOTA performance in the weakly supervised VMR setting, and are even comparable with some fully-supervised VMR methods but with much less annotation cost.
Single-image snow removal aims to restore clean images from heterogeneous and irregular snow degradations. Recent methods utilize neural networks to remove various degradations directly. However, these approaches suffer from the limited ability to flexibly perceive complicated snow degradation patterns and insufficient representation of background structure information. To further improve the performance and generalization ability of snow removal, this paper aims to develop a novel and efficient paradigm from the perspective of degradation perceiving and background modeling. For this purpose, we first analyze two critical properties in real snow images, namely local-region heterogeneity and axial anisotropy. Inspired by them, we propose Dynamic Perceiving for Degraded Regions and Axial-Pooling Attention for Background Structure Modeling, which together couple a new network architecture, dubbed as D2P-BMNet. Our proposed D2P-BMNet offers several key advantages: (i) It can effectively segment regions under the uncertainty map's guidance, and dynamically perceives heterogeneous degradations within various regions. (ii) By utilizing linear attention solely along a horizontal axis, it can effectively model clean scene information that is buried beneath the snow. (iii) D2P-BMNet significantly improves over prior methods across all benchmarks and maintains excellent inference speeds.
Time-of-flight magnetic resonance angiography (TOF-MRA) is a common cerebrovascular imaging. Accurate and automatic cerebrovascular segmentation in TOF-MRA images is an important auxiliary method in clinical practice. Due to the complex semantics and noise interference, the existing segmentation methods often fail to pay attention to topological correlation, resulting in the neglect of branch vessels and vascular topology destruction. In this paper, we proposed a topology regularization adversarial model for cerebrovascular segmentation in TOF-MRA images. Firstly, we trained a self-supervised model to learn spatial semantic layout in TOF-MRA images by image context restoration. Subsequently, we exploited initialization based on the self-supervised model and constructed an adversarial model to accomplish parameter optimization. Considering the limitations of uneven distribution of cerebrovascular classes, we introduced skeleton structures as discriminative features to enhance vessel topological strength. We constructed some latest models to test our method over two datasets. Results show that the proposed model attains the highest score. Therefore, our method can obtain accurate connectivity information and higher graph similarity, leading more meaningful clinical utility.
Focusing on Flexible Masks: A Novel Framework for Panoptic Scene Graph Generation with Relation Constraints
PDF ↗Panoptic Scene Graph Generation (PSG) presents pixel-wise instance detection and localization, leading to comprehensive and precise scene graphs. Current methods employ conventional Scene Graph Generation (SGG) frameworks to solve the PSG problem, neglecting the fundamental differences between bounding boxes and masks, i.e., bounding boxes are allowed overlap but masks are not. Since segmentation from the panoptic head has deviations, non-overlapping masks may not afford complete instance information. Subsequently, in the training phase, incomplete segmented instances may not be well-aligned to annotated ones, causing mismatched relations and insufficient training. During the inference phase, incomplete segmentation leads to incomplete scene graph prediction. To alleviate these problems, we construct a novel two-stage framework for the PSG problem. In the training phase, we design a proposal matching strategy, which replaces deterministic segmentation results with proposals extracted from the off-the-shelf panoptic head for label alignment, thereby ensuring the all-matching of training samples. In the inference phase, we present an innovative concept of employing relation predictions to constrain segmentation and design a relation-constrained segmentation algorithm. By reconstructing the process of generating segmentation results from proposals using predicted relation results, the algorithm recovers more valid instances and predicts more complete scene graphs. The experimental results show overall superiority, effectiveness, and robustness against adversarial attacks.
Semi-supervised semantic segmentation (SSS) is an important task that utilizes both labeled and unlabeled data to reduce expenses on labeling training examples. However, the effectiveness of SSS algorithms is limited by the difficulty of fully exploiting the potential of unlabeled data. To address this, we propose a dual-level Siamese structure network (DSSN) for pixel-wise contrastive learning. By aligning positive pairs with a pixel-wise contrastive loss using strong augmented views in both low-level image space and high-level feature space, the proposed DSSN is designed to maximize the utilization of available unlabeled data. Additionally, we introduce a novel class-aware pseudo-label selection strategy for weak-to-strong supervision, which addresses the limitations of most existing methods that do not perform selection or apply a predefined threshold for all classes. Specifically, our strategy selects the top high-confidence prediction of the weak view for each class to generate pseudo labels that supervise the strong augmented views. This strategy is capable of taking into account the class imbalance and improving the performance of long-tailed classes. Our proposed method achieves state-of-the-art results on two datasets, PASCAL VOC 2012 and Cityscapes, outperforming other SSS algorithms by a significant margin. The source code is available at https://github.com/kunzhan/DSSN.
Existing superpixel segmentation algorithms mainly focus on natural image with high-quality, while neglecting the inevitable environment constraint in complex scenes. In this paper, we propose an end-to-end frequency domain guided superpixel segmentation network (FSNet) to generate superpixels with sharp boundary adherence for complex scenes by fusing the deep features in spatial and frequency domains. To utilize the frequency domain information of the image, an improved frequency information extractor (IFIE) is proposed to extract the frequency domain information with sharp boundary features. Moreover, considering the over-sharp feature may damage the semantic information of superpixel, we further design a dense hybrid atrous convolution (DHAC) block to preserve semantic information via capturing wider and deeper semantic information in spatial domain. Finally, the extracted deep features in spatial and frequency domains will be fused to generate semantic perceptual superpixels with sharp boundary adherence. Extensive experiments on multiple challenging datasets with complex boundaries demonstrate that our method achieves the state-of-the-art performance both quantitatively and qualitatively, and we further verify the superiority of the proposed method when applied in salient object detection.
Video moment retrieval (VMR) aims to search for a video segment that matches the search intent in a query sentence, which has received increasing attention in recent years, due to its practical values in various fields. Existing efforts devoted to this interesting yet challenging task typically encode the query sentence and video segments into unstructured global representations for cross-modal interaction and fusion, which may fail to accurately capture the search intent in complex queries with multi-granularity semantics. To fill the research gap, this paper presents a novel solution termed semantics-enriched video moment retrieval method (SVMR), which can effectively and explicitly model the hierarchical multi-granularity semantics of complex textual query. Specifically, we first explore cross-token relations to offer multiple granularity query representations with hierarchical semantic contexts of semantically associated tokens for fine-grained cross-modal interaction and fusion, which contributes to mining rich visual motion cues semantically related to different activities and entities in complex queries. Furthermore, to fully leverage fine-grained cross-modal cues for moment retrieval, we design a specific temporal boundary reasoning module by explicitly generating start and end time-aware filter kernels with visual cues to perceive the moment boundaries. Extensive experiments and analyses on three public benchmarks clearly demonstrate the advantage of our proposed SVMR over existing state-of-the-art approaches, especially in retrieving complex query-based video moments.
Bird's-Eye-View (BEV) based 3D visual perception, which formulates a unified space for multi-view representation, has received wide attention in autonomous driving due to its scalability for downstream tasks. However, view transform in transformer-based BEV methods is agnostic of 3D occlusion relationships, resulting in model degradation. To construct a higher-quality BEV space, this paper analyzes the mutual occlusion problems in the view transform process and proposes a new transformer-based method named OccluBEV. OccluBEV alleviates the occlusion issue via point cloud information distillation in both the image and BEV space. Specifically, in the image space, we perform depth estimation for each pixel and utilize it to guide image feature mapping. Further, since predicting depth directly from monocular image is ill-posed, ignoring stereo information such as multi-view and temporal cues, this paper introduces a voxel visibility segmentation task in 3D BEV space. The task explicitly predicts whether each voxel in the 3D BEV grid is occupied or not. In addition, to alleviate the overfitting problem in BEV feature learning under a single task, we design a multi-head learning framework which jointly models multiple strongly-correlated tasks in a unified BEV space. The effectiveness of the proposed method is fully validated on the nuScenes dataset, achieving a competetive NDS/mAP score of 57.5/47.9 on the nuScenes test leaderboard using ResNet101 backbone, which is superior to state-of-the-art camera-based solutions.
In recent years, cross-modal domain adaptation has been studied on the paired 2D image and 3D LiDAR data to ease the labeling costs for 3D LiDAR semantic segmentation (3DLSS) in the target domain. However, in such a setting the paired 2D and 3D data in the source domain are still collected with additional effort. Since the 2D-3D projections can enable the 3D model to learn semantic information from the 2D counterpart, we ask whether we could further remove the need of source 3D data and only rely on the source 2D images. To answer it, this paper studies a new 3DLSS setting where a 2D dataset (source) with semantic annotations and a paired but unannotated 2D image and 3D LiDAR data (target) are available1. To achieve 3DLSS in this scenario, we propose Cross-Modal and Cross-Domain Learning (CoMoDaL). Specifically, our CoMoDaL aims at modeling 1) inter-modal cross-domain distillation between the unpaired source 2D image and target 3D LiDAR data, and 2) the intra-domain cross-modal guidance between the target 2D image and 3D LiDAR data pair. In CoMoDaL, we propose to apply several constraints, such as point-to-pixel and prototype-to pixel alignments, to associate the semantics in different modalities and domains by constructing mixed samples in two modalities. The experimental results on several datasets show that in the proposed setting, the developed CoMoDaL can achieve segmentation without the supervision of labeled LiDAR data. Ablations are also conducted to provide more analysis. Code will be available publicly2.
Recent RGB-D semantic segmentation networks are usually manually designed. However, due to limited human efforts and time costs, their performance might be inferior for complex scenarios. To address this issue, we propose the first Neural Architecture Search (NAS) method that designs the network automatically. Specifically, the target network consists of an encoder and a decoder. The encoder is designed with two independent branches, where each branch specializes in extracting features from RGB and depth images, respectively. The decoder fuses the features and generates the final segmentation result. Besides, for automatic network design, we design a grid-like network-level search space combined with a hierarchical cell-level search space. By further developing an effective gradient-based search strategy, the network structure with hierarchical cell architectures is discovered. Extensive results on two datasets show that the proposed method outperforms the state-of-the-art approaches, which achieves a mIoU score of 55.1% on the NYU-Depth v2 dataset and 50.3% on the SUN-RGBD dataset.
Surround-view cameras combined with image depth transformation to 3D feature space and fusion with point cloud features are highly regarded. The transformation of 2D features into 3D feature space by means of predefined sampling points and depth distribution happens throughout the scene, and this process generates a large number of redundant features. In addition, multimodal feature fusion unified in 3D space often happens in the previous step of the downstream task, ignoring the interactive fusion between different scales. To this end, we design a new framework, focusing on the design that can give 3D geometric perception information to images and unify them into voxel space to accomplish multi-scale interactive fusion, and we mitigate feature alignment between modal features by geometric relationships between voxel features. The method has two main designs. First, a Segmentation-guided Image View Transformation module is used to accurately transform the pixel region containing the object into a 3D pseudo-point voxel space with the help of a depth distribution. This allows subsequent feature fusion to be performed in a unified voxel feature. Secondly, a Voxel-centric Consistent Fusion module is used to alleviate the errors caused by depth estimation, as well as to achieve better feature fusion between unified modalities. Through extensive experiments on the KITTI and nuScenes datasets, we validate the effectiveness of our camera-LIDAR fusion method. Our proposed approach shows competitive performance on both datasets and outperforms state-of-the-art methods in certain classes of 3D object detection benchmarks. https://github.com/no-Name128/DLFusion [code release]
Audiovisual self-supervised representation learning has made significant strides in various audiovisual tasks. Existing methods mostly focus on single representation modeling between audio and visual modalities, ignoring the complex correspondence between them, resulting in the inability to execute cross-modal understanding in a more natural audiovisual scene. Several biological studies have shown that human learning is influenced by multi-layered synchronization of perception. To this end, inspired by biology, we argue to exploit the naturally existing relationships in audio and visual modalities to learn audiovisual representations under multilayer perceptual integration. Firstly, we introduce an audiovisual multi-representation pretext task that integrates semantic consistency, temporal alignment, and spatial correspondence. Secondly, we propose a self-supervised audiovisual multi-representation learning approach, which simultaneously learns the perceptual relationship between visual and audio modalities at semantic, temporal, and spatial levels. To establish fine-grained correspondence between visual objects and sounds, an audiovisual object detection module is proposed, which detects potential sounding objects by combining unsupervised knowledge at multiple levels. In addition, we propose a modality-wise loss and a task-wise loss to learn a subspace-orthogonal representation space that makes representation relations more discriminative. Finally, experimental results demonstrate that collectively understanding the semantic, temporal, and spatial correspondence between audiovisual modalities enables the model to perform better on downstream tasks such as sound separation, sound spatialization, and audiovisual segmentation.
Traditional 3D segmentation methods can only recognize a fixed range of classes that appear in the training set, which limits their application in real-world scenarios due to the lack of generalization ability. Large-scale visual-language pre-trained models, such as CLIP, have shown their generalization ability in the zero-shot 2D vision tasks, but are still unable to be applied to 3D semantic segmentation directly. In this work, we focus on zero-shot point cloud semantic segmentation and propose a simple yet effective baseline to transfer the visual-linguistic knowledge implied in CLIP to point cloud encoder at both feature and output levels. Both feature-level and output-level alignments are conducted between 2D and 3D encoders for effective knowledge transfer. Concretely, a Multi-granularity Cross-modal Feature Alignment (MCFA) module is proposed to align 2D and 3D features from global semantic and local position perspectives for feature-level alignment. For the output level, per-pixel pseudo labels of unseen classes are extracted using the pre-trained CLIP model as supervision for the 3D segmentation model to mimic the behavior of the CLIP image encoder. Extensive experiments are conducted on two popular benchmarks of point cloud segmentation. Our method outperforms significantly previous state-of-the-art methods under zero-shot setting (+29.2% mIoU on SemanticKITTI and 31.8% mIoU on nuScenes), and further achieves promising results in the annotation-free point cloud semantic segmentation setting, showing its great potential for label-efficient learning.