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Ngai-Man Cheung

37 accepted papers

2026

Do Vision-Language Models Leak What They Learn? Adaptive Token-Weighted Model Inversion Attacks

CVPR 2026

Model inversion (MI) attacks pose significant privacy risks by reconstructing private training data from trained neural networks. While prior studies have primarily examined unimodal deep networks, the vulnerability of vision-language models (VLMs) remains largely unexplored. In this work, we presen

Cited by 0SourcecodeScholar
2026

How Do Medical MLLMs Fail? A Study on Visual Grounding in Medical Images

ICLR 2026poster

Generalist multimodal large language models (MLLMs) have achieved impressive performance across a wide range of vision-language tasks. However, their performance on medical tasks—particularly in zero-shot settings where generalization is critical—remains suboptimal. A key research gap is the limited…

Cited by 0SourceScholar
2026

SAVER: Mitigating Hallucinations in Large Vision-Language Models via Style-Aware Visual Early Revision

AAAI 2026technical

Large Vision-Language Models (LVLMs) recently achieve significant breakthroughs in understanding complex visual-textual contexts. However, hallucination issues still limit their real-world applicability. Although previous mitigation methods effectively reduce hallucinations in photographic images, t

Cited by 0SourcePDFScholar
2024

FairQueue: Rethinking Prompt Learning for Fair Text-to-Image Generation

NeurIPS 2024poster

Recently, prompt learning has emerged as the state-of-the-art (SOTA) for fair text-to-image (T2I) generation. Specifically, this approach leverages readily available reference images to learn inclusive prompts for each target Sensitive Attribute (tSA), allowing for fair image generation. In this wor…

2024

Model Inversion Robustness: Can Transfer Learning Help?

CVPR 2024poster

Model Inversion (MI) attacks aim to reconstruct private training data by abusing access to machine learning models. Contemporary MI attacks have achieved impressive attack performance posing serious threats to privacy. Meanwhile all existing MI defense methods rely on regularization that is in direc…

2024

On the Vulnerability of Skip Connections to Model Inversion Attacks

ECCV 2024poster

"Skip connections are fundamental architecture designs for modern deep neural networks (DNNs) such as CNNs and ViTs. While they help improve model performance significantly, we identify a vulnerability associated with skip connections to Model Inversion (MI) attacks, a type of privacy attack that ai…

2024

Vision Transformer Neural Architecture Search for Out-of-Distribution Generalization: Benchmark and Insights

NeurIPS 2024poster

While Vision Transformer (ViT) have achieved success across various machine learning tasks, deploying them in real-world scenarios faces a critical challenge: generalizing under Out-of-Distribution (OoD) shifts. A crucial research gap remains in understanding how to design ViT architectures – both m…

2023

Exploring Incompatible Knowledge Transfer in Few-Shot Image Generation

CVPR 2023poster

Few-shot image generation (FSIG) learns to generate diverse and high-fidelity images from a target domain using a few (e.g., 10) reference samples. Existing FSIG methods select, preserve and transfer prior knowledge from a source generator (pretrained on a related domain) to learn the target generat…

2023

Fair Generative Models via Transfer Learning

AAAI 2023technical

This work addresses fair generative models. Dataset biases have been a major cause of unfairness in deep generative models. Previous work had proposed to augment large, biased datasets with small, unbiased reference datasets. Under this setup, a weakly-supervised approach has been proposed, which ac…

2023

Label-Only Model Inversion Attacks via Knowledge Transfer

NeurIPS 2023poster

In a model inversion (MI) attack, an adversary abuses access to a machine learning (ML) model to infer and reconstruct private training data. Remarkable progress has been made in the white-box and black-box setups, where the adversary has access to the complete model or the model's soft output respe…

2023

On Evaluating Adversarial Robustness of Large Vision-Language Models

NeurIPS 2023poster

Large vision-language models (VLMs) such as GPT-4 have achieved unprecedented performance in response generation, especially with visual inputs, enabling more creative and adaptable interaction than large language models such as ChatGPT. Nonetheless, multimodal generation exacerbates safety concerns…

2023

Re-Thinking Model Inversion Attacks Against Deep Neural Networks

CVPR 2023poster

Model inversion (MI) attacks aim to infer and reconstruct private training data by abusing access to a model. MI attacks have raised concerns about the leaking of sensitive information (e.g. private face images used in training a face recognition system). Recently, several algorithms for MI have bee…

2022

Discovering Transferable Forensic Features for CNN-Generated Images Detection

ECCV 2022poster

"Visual counterfeits are increasingly causing an existential conundrum in mainstream media with rapid evolution in neural image synthesis methods. Though detection of such counterfeits has been a taxing problem in the image forensics community, a recent class of forensic detectors -- universal detec…

2022

Few-shot Image Generation via Adaptation-Aware Kernel Modulation

NeurIPS 2022accept

Few-shot image generation (FSIG) aims to learn to generate new and diverse samples given an extremely limited number of samples from a domain, e.g., 10 training samples. Recent work has addressed the problem using transfer learning approach, leveraging a GAN pretrained on a large-scale source domain…

2022

Graph-Wise Common Latent Factor Extraction for Unsupervised Graph Representation Learning

AAAI 2022technical

Unsupervised graph-level representation learning plays a crucial role in a variety of tasks such as molecular property prediction and community analysis, especially when data annotation is expensive. Currently, most of the best-performing graph embedding methods are based on Infomax principle. The p…

2022

Revisiting Label Smoothing and Knowledge Distillation Compatibility: What was Missing?

ICML 2022spotlight

This work investigates the compatibility between label smoothing (LS) and knowledge distillation (KD). Contemporary findings addressing this thesis statement take dichotomous standpoints: Muller et al. (2019) and Shen et al. (2021b). Critically, there is no effort to understand and resolve these con…

2021

A Closer Look at Fourier Spectrum Discrepancies for CNN-Generated Images Detection

CVPR 2021poster

CNN-based generative modelling has evolved to produce synthetic images indistinguishable from real images in the RGB pixel space. Recent works have observed that CNN-generated images share a systematic shortcoming in replicating high frequency Fourier spectrum decay attributes. Furthermore, these wo…

Cited by 99PDFcodeScholar
2021

Revisit Multimodal Meta-Learning through the Lens of Multi-Task Learning

NeurIPS 2021poster

Multimodal meta-learning is a recent problem that extends conventional few-shot meta-learning by generalizing its setup to diverse multimodal task distributions. This setup makes a step towards mimicking how humans make use of a diverse set of prior skills to learn new skills. Previous work has achi…

2020

Direct Quantization for Training Highly Accurate Low Bit-width Deep Neural Networks

IJCAI 2020poster

This paper proposes two novel techniques to train deep convolutional neural networks with low bit-width weights and activations. First, to obtain low bit-width weights, most existing methods obtain the quantized weights by performing quantization on the full-precision network weights. However, this…

2019

Deep Clustering by Gaussian Mixture Variational Autoencoders With Graph Embedding

ICCV 2019poster

We propose DGG: D eep clustering via a G aussian-mixture variational autoencoder (VAE) with G raph embedding. To facilitate clustering, we apply Gaussian mixture model (GMM) as the prior in VAE. To handle data with complex spread, we apply graph embedding. Our idea is that graph information which…

Cited by 154PDFcodeScholar
2019

SDRSAC: Semidefinite-Based Randomized Approach for Robust Point Cloud Registration Without Correspondences

CVPR 2019oral

This paper presents a novel randomized algorithm for robust point cloud registration without correspondences. Most existing registration approaches require a set of putative correspondences obtained by extracting invariant descriptors. However, such descriptors could become unreliable in noisy and c…

Cited by 114PDFcodeScholar
2018

Fine-Grained Wound Tissue Analysis Using Deep Neural Network

ICASSP 2018accepted

Tissue assessment for chronic wounds is the basis of wound grading and selection of treatment approaches. While several image processing approaches have been proposed for automatic wound tissue analysis, there has been a shortcoming in these approaches for clinical practices. In particular, seemingl…

Cited by 0SourceScholar
2017

Non-Rigid Object Tracking via Deformable Patches Using Shape-Preserved KCF and Level Sets

ICCV 2017poster

Part-based trackers are effective in exploiting local details of the target object for robust tracking. In contrast to most existing part-based methods that divide all kinds of target objects into a number of fixed rectangular patches, in this paper, we propose a novel framework in which a set of de…

Cited by 26PDFScholar
2017

Simultaneous Feature Aggregating and Hashing for Large-Scale Image Search

CVPR 2017poster

In most state-of-the-art hashing-based visual search systems, local image descriptors of an image are first aggregated as a single feature vector. This feature vector is then subjected to a hashing function that produces a binary hash code. In previous work, the aggregating and the hashing processes…

Cited by 40PDFScholar
2017

Simultaneous low-rank component and graph estimation for high-dimensional graph signals: Application to brain imaging

ICASSP 2017accepted

We propose an algorithm to uncover the intrinsic low-rank component of a high-dimensional, graph-smooth and grossly-corrupted dataset, under the situations that the underlying graph is unknown. Based on a model with a low-rank component plus a sparse perturbation, and an initial graph estimation, ou…

Cited by 0SourceScholar
2016

Egocentric activity recognition with multimodal fisher vector

ICASSP 2016accepted

With the increasing availability of wearable devices, research on egocentric activity recognition has received much attention recently. In this paper, we build a Multimodal Egocentric Activity dataset which includes egocentric videos and sensor data of 20 fine-grained and diverse activity categories…

Cited by 0SourceScholar
2015

FAemb: A Function Approximation-Based Embedding Method for Image Retrieval

CVPR 2015poster

The objective of this paper is to design an embedding method mapping local features describing image (e.g. SIFT) to a higher dimensional representation used for image retrieval problem. By investigating the relationship between the linear approximation of a nonlinear function in high dimensional spa…

Cited by 37SourcePDFScholar
2015

The efficiency of view synthesis prediction for 3D video coding: A spectral domain analysis

ICASSP 2015accepted

We study the coding efficiency of view synthesis prediction (VSP) in 3D video coding. Our spectral domain analysis relates the power spectral density (PSD) of the VSP prediction error to the probability density function (pdf) of the warping error. Our analysis takes into account the warping error in…

Cited by 0SourceScholar