We introduce SynCLR a novel approach for learning visual representations exclusively from synthetic images without any real data. We synthesize a large dataset of image captions using LLMs then use an off-the-shelf text-to-image model to generate multiple images corresponding to each synthetic caption. We perform visual representation learning on these synthetic images via contrastive learning treating images sharing the same caption as positive pairs. The resulting representations demonstrate remarkable transferability competing favorably with other general-purpose visual representation learners such as CLIP and DINO v2 in image classification tasks. Furthermore in dense prediction tasks such as semantic segmentation SynCLR outperforms previous self-supervised methods by a significant margin e.g. improving over MAE and iBOT by 5.0 and 3.1 mIoU on ADE20k for ViT-B/16.
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Quantized neural networks employ reduced precision representations for both weights and activations. This quantization process significantly reduces the memory requirements and computational complexity of the network. Binary Neural Networks (BNNs) are the extreme quantization case representing values with just one bit. Since the sign function is typically used to map real values to binary values smooth approximations are introduced to mimic the gradients during error backpropagation. Thus the mismatch between the forward and backward models corrupts the direction of the gradient causing training inconsistency problems and performance degradation. In contrast to current BNN approaches we propose to employ a binary periodic (BiPer) function during binarization. Specifically we use a square wave for the forward pass to obtain the binary values and employ the trigonometric sine function with the same period of the square wave as a differentiable surrogate during the backward pass. We demonstrate that this approach can control the quantization error by using the frequency of the periodic function and improves network performance. Extensive experiments validate the effectiveness of BiPer in benchmark datasets and network architectures with improvements of up to 1% and 0.69% with respect to state-of-the-art methods in the classification task over CIFAR-10 and ImageNet respectively. Our code is publicly available at https://github.com/edmav4/BiPer.
As a problem often encountered in real-world scenarios multi-view multi-label learning has attracted considerable research attention. However due to oversights in data collection and uncertainties in manual annotation real-world data often suffer from incompleteness. Regrettably most existing multi-view multi-label learning methods sidestep missing views and labels. Furthermore they often neglect the potential of harnessing complementary information between views and labels thus constraining their classification capabilities. To address these challenges we propose a view-category interactive sharing transformer tailored for incomplete multi-view multi-label learning. Within this network we incorporate a two-layer transformer module to characterize the interplay between views and labels. Additionally to address view incompleteness a KNN-style missing view generation module is employed. Finally we introduce a view-category consistency guided embedding enhancement module to align different views and improve the discriminating power of the embeddings. Collectively these modules synergistically integrate to classify the incomplete multi-view multi-label data effectively. Extensive experiments substantiate that our approach outperforms the existing state-of-the-art methods.
The zero-shot performance of existing vision-language models (VLMs) such as CLIP is limited by the availability of large-scale aligned image and text datasets in specific domains. In this work we leverage two complementary sources of information -- descriptions of categories generated by large language models (LLMs) and abundant fine-grained image classification datasets -- to improve the zero-shot classification performance of VLMs across fine-grained domains. On the technical side we develop methods to train VLMs with this "bag-level" image-text supervision. We find that simply using these attributes at test-time does not improve performance but our training strategy for example on the iNaturalist dataset leads to an average improvement of 4-5% in zero-shot classification accuracy for novel categories of birds and flowers. Similar improvements are observed in domains where a subset of the categories was used to fine-tune the model. By prompting LLMs in various ways we generate descriptions that capture visual appearance habitat and geographic regions and pair them with existing attributes such as the taxonomic structure of the categories. We systematically evaluate their ability to improve zero-shot categorization in natural domains. Our findings suggest that geographic priors can be just as effective and are complementary to visual appearance. Our method also outperforms prior work on prompt-based tuning of VLMs. We release the benchmark consisting of 14 datasets at https://github.com/cvl-umass/AdaptCLIPZS which will contribute to future research in zero-shot recognition.
With the prevalence of the Pretraining-Finetuning paradigm in transfer learning the robustness of downstream tasks has become a critical concern. In this work we delve into adversarial robustness in transfer learning and reveal the critical role of initialization including both the pretrained model and the linear head. First we discover the necessity of an adversarially robust pretrained model. Specifically we reveal that with a standard pretrained model Parameter-Efficient Finetuning (PEFT) methods either fail to be adversarially robust or continue to exhibit significantly degraded adversarial robustness on downstream tasks even with adversarial training during finetuning. Leveraging a robust pretrained model surprisingly we observe that a simple linear probing can outperform full finetuning and other PEFT methods with random initialization on certain datasets. We further identify that linear probing excels in preserving robustness from the robust pretraining. Based on this we propose Robust Linear Initialization (RoLI) for adversarial finetuning which initializes the linear head with the weights obtained by adversarial linear probing to maximally inherit the robustness from pretraining. Across five different image classification datasets we demonstrate the effectiveness of RoLI and achieve new state-of-the-art results. Our code is available at https://github.com/DongXzz/RoLI.
Redundancy is a persistent challenge in Capsule Networks (CapsNet) leading to high computational costs and parameter counts. Although previous studies have introduced pruning after the initial capsule layer dynamic routing's fully connected nature and non-orthogonal weight matrices reintroduce redundancy in deeper layers. Besides dynamic routing requires iterating to converge further increasing computational demands. In this paper we propose an Orthogonal Capsule Network (OrthCaps) to reduce redundancy improve routing performance and decrease parameter counts. Firstly an efficient pruned capsule layer is introduced to discard redundant capsules. Secondly dynamic routing is replaced with orthogonal sparse attention routing eliminating the need for iterations and fully connected structures. Lastly weight matrices during routing are orthogonalized to sustain low capsule similarity which is the first approach to use Householder orthogonal decomposition to enforce orthogonality in CapsNet. Our experiments on baseline datasets affirm the efficiency and robustness of OrthCaps in classification tasks in which ablation studies validate the criticality of each component. OrthCaps-Shallow outperforms other Capsule Network benchmarks on four datasets utilizing only 110k parameters - a mere 1.25% of a standard Capsule Network's total. To the best of our knowledge it achieves the smallest parameter count among existing Capsule Networks. Similarly OrthCaps-Deep demonstrates competitive performance across four datasets utilizing only 1.2% of the parameters required by its counterparts.
Facial Attribute Classification (FAC) holds substantial promise in widespread applications. However FAC models trained by traditional methodologies can be unfair by exhibiting accuracy inconsistencies across varied data subpopulations. This unfairness is largely attributed to bias in data where some spurious attributes (e.g. Male) statistically correlate with the target attribute (e.g. Smiling). Most of existing fairness-aware methods rely on the labels of spurious attributes which may be unavailable in practice. This work proposes a novel generation-based two-stage framework to train a fair FAC model on biased data without additional annotation. Initially we identify the potential spurious attributes based on generative models. Notably it enhances interpretability by explicitly showing the spurious attributes in image space. Following this for each image we first edit the spurious attributes with a random degree sampled from a uniform distribution while keeping target attribute unchanged. Then we train a fair FAC model by fostering model invariance to these augmentation. Extensive experiments on three common datasets demonstrate the effectiveness of our method in promoting fairness in FAC without compromising accuracy. Codes are in https://github.com/heqianpei/DiGA.
Oriented object detection has witnessed significant progress in recent years. However the impressive performance of oriented object detectors is at the huge cost of labor-intensive annotations and deteriorates once the annotated data becomes limited. Semi-supervised learning in which sufficient unannotated data are utilized to enhance the base detector is a promising method to address the annotation deficiency problem. Motivated by weakly supervised learning we introduce annotation-efficient point annotations for unannotated images and propose a weakly semi-supervised method for oriented object detection to balance the detection performance and annotation cost. Specifically we propose a Rotation-Modulated Relational Graph Matching method to match relations of proposals centered on annotated points between different models to alleviate the ambiguity of point annotations in depicting the oriented object. In addition we further propose a Relational Rank Distribution Matching method to align the rank distribution on classification and regression between different models. Finally to handle the difficult annotated points that both models are confused about we introduce weakly supervised learning to impose positive signals for difficult point-induced clusters to the base model and focus the base model on the occupancy between the predictions and annotated points. We perform extensive experiments on challenging datasets to demonstrate the effectiveness of our proposed weakly semi-supervised method in effectively leveraging unannotated data for significant performance improvement.
Anomaly detection (AD) aims to identify defective images and localize their defects (if any). Ideally AD models should be able to detect defects over many image classes; without relying on hard-coded class names that can be uninformative or inconsistent across datasets; learn without anomaly supervision; and be robust to the long-tailed distributions of real-world applications. To address these challenges we formulate the problem of long-tailed AD by introducing several datasets with different levels of class imbalance and metrics for performance evaluation. We then propose a novel method LTAD to detect defects from multiple and long-tailed classes without relying on dataset class names. LTAD combines AD by reconstruction and semantic AD modules. AD by reconstruction is implemented with a transformer-based reconstruction module. Semantic AD is implemented with a binary classifier which relies on learned pseudo class names and a pretrained foundation model. These modules are learned over two phases. Phase 1 learns the pseudo-class names and a variational autoencoder (VAE) for feature synthesis that augments the training data to combat long-tails. Phase 2 then learns the parameters of the reconstruction and classification modules of LTAD. Extensive experiments using the proposed long-tailed datasets show that LTAD substantially outperforms the state-of-the-art methods for most forms of dataset imbalance. The long-tailed dataset split is available at https://zenodo.org/records/10854201
Annotating datasets for object detection is an expensive and time-consuming endeavor. To minimize this burden active learning (AL) techniques are employed to select the most informative samples for annotation within a constrained "annotation budget". Traditional AL strategies typically rely on model uncertainty or sample diversity for query sampling while more advanced methods have focused on developing AL-specific object detector architectures to enhance performance. However these specialized approaches are not readily adaptable to different object detectors due to the significant engineering effort required for integration. To overcome this challenge we introduce Plug and Play Active Learning (PPAL) a simple and effective AL strategy for object detection. PPAL is a two-stage method comprising uncertainty-based and diversity-based sampling phases. In the first stage our Difficulty Calibrated Uncertainty Sampling leverage a category-wise difficulty coefficient that combines both classification and localisation difficulties to re-weight instance uncertainties from which we sample a candidate pool for the subsequent diversity-based sampling. In the second stage we propose Category Conditioned Matching Similarity to better compute the similarities of multi-instance images as ensembles of their instance similarities which is used by the k-Means++ algorithm to sample the final AL queries. PPAL makes no change to model architectures or detector training pipelines; hence it can be easily generalized to different object detectors. We benchmark PPAL on the MS-COCO and Pascal VOC datasets using different detector architectures and show that our method outperforms prior work by a large margin. Code is available at https://github.com/ChenhongyiYang/PPAL
In this paper we address web-scale visual entity recognition specifically the task of mapping a given query image to one of the 6 million existing entities in Wikipedia. One way of approaching a problem of such scale is using dual encoder models (e.g. CLIP) where all the entity names and query images are embedded into a unified space paving the way for an approximate kNN search. Alternatively it is also possible to re-purpose a captioning model to directly generate the entity names for a given image. In contrast we introduce a novel Generative Entity Recognition (GER) framework which given an input image learns to auto-regressively decode a semantic and discriminative "code" identifying the target entity. Our experiments demonstrate the efficacy of this GER paradigm showcasing state-of-the-art performance on the challenging OVEN benchmark. GER surpasses strong captioning dual-encoder visual matching and hierarchical classification baselines affirming its advantage in tackling the complexities of web-scale recognition.
For privacy and security concerns the need to erase unwanted information from pre-trained vision models is becoming evident nowadays. In real-world scenarios erasure requests originate at any time from both users and model owners. These requests usually form a sequence. Therefore under such a setting selective information is expected to be continuously removed from a pre-trained model while maintaining the rest. We define this problem as continual forgetting and identify two key challenges. (i) For unwanted knowledge efficient and effective deleting is crucial. (ii) For remaining knowledge the impact brought by the forgetting procedure should be minimal. To address them we propose Group Sparse LoRA (GS-LoRA). Specifically towards (i) we use LoRA modules to fine-tune the FFN layers in Transformer blocks for each forgetting task independently and towards (ii) a simple group sparse regularization is adopted enabling automatic selection of specific LoRA groups and zeroing out the others. GS-LoRA is effective parameter-efficient data-efficient and easy to implement. We conduct extensive experiments on face recognition object detection and image classification and demonstrate that GS-LoRA manages to forget specific classes with minimal impact on other classes. Codes will be released on https://github.com/bjzhb666/GS-LoRA.
Event cameras characterized by high temporal resolution high dynamic range low power consumption and high pixel bandwidth offer unique capabilities for object detection in specialized contexts. Despite these advantages the inherent sparsity and asynchrony of event data pose challenges to existing object detection algorithms. Spiking Neural Networks (SNNs) inspired by the way the human brain codes and processes information offer a potential solution to these difficulties. However their performance in object detection using event cameras is limited in current implementations. In this paper we propose the Spiking Fusion Object Detector (SFOD) a simple and efficient approach to SNN-based object detection. Specifically we design a Spiking Fusion Module achieving the first-time fusion of feature maps from different scales in SNNs applied to event cameras. Additionally through integrating our analysis and experiments conducted during the pretraining of the backbone network on the NCAR dataset we delve deeply into the impact of spiking decoding strategies and loss functions on model performance. Thereby we establish state-of-the-art classification results based on SNNs achieving 93.7% accuracy on the NCAR dataset. Experimental results on the GEN1 detection dataset demonstrate that the SFOD achieves a state-of-the-art mAP of 32.1% outperforming existing SNN-based approaches. Our research not only underscores the potential of SNNs in object detection with event cameras but also propels the advancement of SNNs. Code is available at https://github.com/yimeng-fan/SFOD.
Discriminative Sample-Guided and Parameter-Efficient Feature Space Adaptation for Cross-Domain Few-Shot Learning
PDF ↗In this paper we look at cross-domain few-shot classification which presents the challenging task of learning new classes in previously unseen domains with few labelled examples. Existing methods though somewhat effective encounter several limitations which we alleviate through two significant improvements. First we introduce a lightweight parameter-efficient adaptation strategy to address overfitting associated with fine-tuning a large number of parameters on small datasets. This strategy employs a linear transformation of pre-trained features significantly reducing the trainable parameter count. Second we replace the traditional nearest centroid classifier with a discriminative sample-aware loss function enhancing the model's sensitivity to the inter- and intra-class variances within the training set for improved clustering in feature space. Empirical evaluations on the Meta-Dataset benchmark showcase that our approach not only improves accuracy up to 7.7% and 5.3% on previously seen and unseen datasets respectively but also achieves the above performance while being at least 3x more parameter-efficient than existing methods establishing a new state-of-the-art in cross-domain few-shot learning. Our code is available at https://github.com/rashindrie/DIPA.
Deep neural networks for learning Symmetric Positive Definite (SPD) matrices are gaining increasing attention in machine learning. Despite the significant progress most existing SPD networks use traditional Euclidean classifiers on an approximated space rather than intrinsic classifiers that accurately capture the geometry of SPD manifolds. Inspired by Hyperbolic Neural Networks (HNNs) we propose Riemannian Multinomial Logistics Regression (RMLR) for the classification layers in SPD networks. We introduce a unified framework for building Riemannian classifiers under the metrics pulled back from the Euclidean space and showcase our framework under the parameterized Log-Euclidean Metric (LEM) and Log-Cholesky Metric (LCM). Besides our framework offers a novel intrinsic explanation for the most popular LogEig classifier in existing SPD networks. The effectiveness of our method is demonstrated in three applications: radar recognition human action recognition and electroencephalography (EEG) classification. The code is available at https://github.com/GitZH-Chen/SPDMLR.git.
Recent advancements in Large Vision-Language Models (VLMs) have shown great promise in natural image domains allowing users to hold a dialogue about given visual content. However such general-domain VLMs perform poorly for Remote Sensing (RS) scenarios leading to inaccurate or fabricated information when presented with RS domain-specific queries. Such a behavior emerges due to the unique challenges introduced by RS imagery. For example to handle high-resolution RS imagery with diverse scale changes across categories and many small objects region-level reasoning is necessary alongside holistic scene interpretation. Furthermore the lack of domain-specific multimodal instruction following data as well as strong backbone models for RS make it hard for the models to align their behavior with user queries. To address these limitations we propose GeoChat - the first versatile remote sensing VLM that offers multitask conversational capabilities with high-resolution RS images. Specifically GeoChat can not only answer image-level queries but also accepts region inputs to hold region-specific dialogue. Furthermore it can visually ground objects in its responses by referring to their spatial coordinates. To address the lack of domain-specific datasets we generate a novel RS multimodal instruction-following dataset by extending image-text pairs from existing diverse RS datasets. Leveraging this rich dataset we fine-tune our remote sensing VLM based on the LLaVA-1.5 architecture. We establish a comprehensive benchmark for RS multitask conversations and compare with a number of baseline methods. GeoChat demonstrates robust zero-shot performance on various remote sensing tasks e.g. image and region captioning visual question answering scene classification visually grounded conversations and referring object detection. Our codes will be open-sourced.
Aiming to advance AI agents large foundation models significantly improve reasoning and instruction execution yet the current focus on vision and language neglects the potential of perceiving diverse modalities in open-world environments. However the success of data-driven vision and language models is costly or even infeasible to be reproduced for rare modalities. In this paper we present ViT-Lens that facilitates efficient omni-modal representation learning by perceiving novel modalities with a pretrained ViT and aligning them to a pre-defined space. Specifically the modality-specific lens is tuned to project any-modal signals to an intermediate embedding space which are then processed by a strong ViT with pre-trained visual knowledge. The encoded representations are optimized toward aligning with the modal-independent space pre-defined by off-the-shelf foundation models. ViT-Lens provides a unified solution for representation learning of increasing modalities with two appealing advantages: (i) Unlocking the great potential of pretrained ViTs to novel modalities effectively with efficient data regime; (ii) Enabling emergent downstream capabilities through modality alignment and shared ViT parameters. We tailor ViT-Lens to learn representations for 3D point cloud depth audio tactile and EEG and set new state-of-the-art results across various understanding tasks such as zero-shot classification. By seamlessly integrating ViT-Lens into Multimodal Foundation Models we enable Any-modality to Text and Image Generation in a zero-shot manner. Code and models are available at https://github.com/TencentARC/ViT-Lens.
Post-training quantization (PTQ) is an efficient model compression technique that quantizes a pretrained full-precision model using only a small calibration set of unlabeled samples without retraining. PTQ methods for convolutional neural networks (CNNs) provide quantization results comparable to full-precision counterparts. Directly applying them to vision transformers (ViTs) however incurs severe performance degradation mainly due to the differences in architectures between CNNs and ViTs. In particular the distribution of activations for each channel vary drastically according to input instances making PTQ methods for CNNs inappropriate for ViTs. To address this we introduce instance-aware group quantization for ViTs (IGQ-ViT). To this end we propose to split the channels of activation maps into multiple groups dynamically for each input instance such that activations within each group share similar statistical properties. We also extend our scheme to quantize softmax attentions across tokens. In addition the number of groups for each layer is adjusted to minimize the discrepancies between predictions from quantized and full-precision models under a bit-operation (BOP) constraint. We show extensive experimental results on image classification object detection and instance segmentation with various transformer architectures demonstrating the effectiveness of our approach.
Logit knowledge distillation attracts increasing attention due to its practicality in recent studies. However it often suffers inferior performance compared to the feature knowledge distillation. In this paper we argue that existing logit-based methods may be sub-optimal since they only leverage the global logit output that couples multiple semantic knowledge. This may transfer ambiguous knowledge to the student and mislead its learning. To this end we propose a simple but effective method i.e. Scale Decoupled Distillation (SDD) for logit knowledge distillation. SDD decouples the global logit output into multiple local logit outputs and establishes distillation pipelines for them. This helps the student to mine and inherit fine-grained and unambiguous logit knowledge. Moreover the decoupled knowledge can be further divided into consistent and complementary logit knowledge that transfers the semantic information and sample ambiguity respectively. By increasing the weight of complementary parts SDD can guide the student to focus more on ambiguous samples improving its discrimination ability. Extensive experiments on several benchmark datasets demonstrate the effectiveness of SDD for wide teacher-student pairs especially in the fine-grained classification task. Code is available at: \href https://github.com/shicaiwei123/SDD-CVPR2024 https://github.com/shicaiwei123/SDD-CVPR2024
The design of deep network architectures and training methods in computer vision has been well-explored. However in almost all cases the images have been used as provided with little exploration of pre-processing steps beyond normalization and data augmentation. Virtually all images posted on the web or captured by devices are processed for viewing by humans. Is the pipeline used for humans also best for use by computers and deep networks? The human visual system uses logarithmic sensors; differences and sums correspond to ratios and products. Features in log space will be invariant to intensity changes and robust to color balance changes. Log RGB space also reveals structure that is corrupted by typical pre-processing. We explore using linear and log RGB data for training standard backbone architectures on an image classification task using data derived directly from RAW images to guarantee its integrity. We found that networks trained on log RGB data exhibit improved performance on an unmodified test set and invariance to intensity and color balance modifications without additional training or data augmentation. Furthermore we found that the gains from using high quality log data could also be partially or fully realized from data in 8-bit sRGB-JPG format by inverting the sRGB transform and taking the log. These results imply existing databases may benefit from this type of pre-processing. While working with log data we found it was critical to retain the integrity of the log relationships and that networks using log data train best with meta-parameters different than those used for sRGB or linear data. Finally we introduce a new 10-category 10k RAW image data set (RAW10) for image classification and other purposes to enable further the exploration of log RGB as an input format for deep networks in computer vision.