Search Results for author: Christopher Zach

Found 37 papers, 10 papers with code

Text in the Dark: Extremely Low-Light Text Image Enhancement

no code implementations22 Apr 2024 Che-Tsung Lin, Chun Chet Ng, Zhi Qin Tan, Wan Jun Nah, Xinyu Wang, Jie Long Kew, PoHao Hsu, Shang Hong Lai, Chee Seng Chan, Christopher Zach

We also labeled texts in the extremely low-light See In the Dark (SID) and ordinary LOw-Light (LOL) datasets to allow for objective assessment of extremely low-light image enhancement through scene text tasks.

Low-Light Image Enhancement Scene Text Detection +1

Two Tales of Single-Phase Contrastive Hebbian Learning

1 code implementation13 Feb 2024 Rasmus Kjær Høier, Christopher Zach

The search for ``biologically plausible'' learning algorithms has converged on the idea of representing gradients as activity differences.

Adversarial Robustness

Learned Trajectory Embedding for Subspace Clustering

no code implementations CVPR 2024 Yaroslava Lochman, Carl Olsson, Christopher Zach

Clustering multiple motions from observed point trajectories is a fundamental task in understanding dynamic scenes.

Clustering Motion Segmentation

Fully Variational Noise-Contrastive Estimation

no code implementations4 Apr 2023 Christopher Zach

By using the underlying theory of proper scoring rules, we design a family of noise-contrastive estimation (NCE) methods that are tractable for latent variable models.

Dual Propagation: Accelerating Contrastive Hebbian Learning with Dyadic Neurons

1 code implementation2 Feb 2023 Rasmus Høier, D. Staudt, Christopher Zach

Activity difference based learning algorithms-such as contrastive Hebbian learning and equilibrium propagation-have been proposed as biologically plausible alternatives to error back-propagation.

Extremely Low-light Image Enhancement with Scene Text Restoration

1 code implementation1 Apr 2022 PoHao Hsu, Che-Tsung Lin, Chun Chet Ng, Jie-Long Kew, Mei Yih Tan, Shang-Hong Lai, Chee Seng Chan, Christopher Zach

Deep learning-based methods have made impressive progress in enhancing extremely low-light images - the image quality of the reconstructed images has generally improved.

Image Restoration Low-Light Image Enhancement +2

Bilevel Programs Meet Deep Learning: A Unifying View on Inference Learning Methods

no code implementations15 May 2021 Christopher Zach

In this work we unify a number of inference learning methods, that are proposed in the literature as alternative training algorithms to the ones based on regular error back-propagation.

Bilevel Optimization

Escaping Poor Local Minima in Large Scale Robust Estimation

no code implementations22 Feb 2021 Huu Le, Christopher Zach

Robust parameter estimation is a crucial task in several 3D computer vision pipelines such as Structure from Motion (SfM).

Progressive Batching for Efficient Non-linear Least Squares

1 code implementation21 Oct 2020 Huu Le, Christopher Zach, Edward Rosten, Oliver J. Woodford

Non-linear least squares solvers are used across a broad range of offline and real-time model fitting problems.

Stochastic Optimization

Lifted Regression/Reconstruction Networks

no code implementations7 May 2020 Rasmus Kjær Høier, Christopher Zach

In this work we propose lifted regression/reconstruction networks (LRRNs), which combine lifted neural networks with a guaranteed Lipschitz continuity property for the output layer.

regression

A Graduated Filter Method for Large Scale Robust Estimation

1 code implementation CVPR 2020 Huu Le, Christopher Zach

Due to the highly non-convex nature of large-scale robust parameter estimation, avoiding poor local minima is challenging in real-world applications where input data is contaminated by a large or unknown fraction of outliers.

Truncated Inference for Latent Variable Optimization Problems: Application to Robust Estimation and Learning

no code implementations ECCV 2020 Christopher Zach, Huu Le

Optimization problems with an auxiliary latent variable structure in addition to the main model parameters occur frequently in computer vision and machine learning.

BIG-bench Machine Learning

SG-VAE: Scene Grammar Variational Autoencoder to generate new indoor scenes

no code implementations ECCV 2020 Pulak Purkait, Christopher Zach, Ian Reid

Our method learns the co-occurrences, and appearance parameters such as shape and pose, for different objects categories through a grammar-based auto-encoder, resulting in a compact and accurate representation for scene layouts.

valid

Pareto Meets Huber: Efficiently Avoiding Poor Minima in Robust Estimation

no code implementations ICCV 2019 Christopher Zach, Guillaume Bourmaud

Robust cost optimization is the task of fitting parameters to data points containing outliers.

Monocular 3D Object Detection and Box Fitting Trained End-to-End Using Intersection-over-Union Loss

no code implementations19 Jun 2019 Eskil Jörgensen, Christopher Zach, Fredrik Kahl

We show how modeling heteroscedastic uncertainty improves performance upon our baseline, and furthermore, how back-propagation can be done through the optimizer in order to train the pipeline end-to-end for additional accuracy.

Autonomous Driving Monocular 3D Object Detection +2

Seeing Behind Things: Extending Semantic Segmentation to Occluded Regions

no code implementations7 Jun 2019 Pulak Purkait, Christopher Zach, Ian Reid

In our experiments we demonstrate that a CNN trained by minimizing the proposed loss is able to predict semantic categories for visible and occluded object parts without requiring to increase the network size (compared to a standard segmentation task).

Segmentation Semantic Segmentation

Contrastive Learning for Lifted Networks

no code implementations7 May 2019 Christopher Zach, Virginia Estellers

In this work we address supervised learning of neural networks via lifted network formulations.

Contrastive Learning

Descending, lifting or smoothing: Secrets of robust cost optimization

no code implementations ECCV 2018 Christopher Zach, Guillaume Bourmaud

Robust cost optimization is the challenging task of fitting a large number of parameters to data points containing a significant and unknown fraction of outliers.

Weakly supervised learning of indoor geometry by dual warping

1 code implementation10 Aug 2018 Pulak Purkait, Ujwal Bonde, Christopher Zach

A major element of depth perception and 3D understanding is the ability to predict the 3D layout of a scene and its contained objects for a novel pose.

Weakly-supervised Learning

pOSE: Pseudo Object Space Error for Initialization-Free Bundle Adjustment

no code implementations CVPR 2018 Je Hyeong Hong, Christopher Zach

Bundle adjustment is a nonlinear refinement method for camera poses and 3D structure requiring sufficiently good initialization.

Maximum Consensus Parameter Estimation by Reweighted $\ell_1$ Methods

no code implementations22 Mar 2018 Pulak Purkait, Christopher Zach, Anders Eriksson

Robust parameter estimation in computer vision is frequently accomplished by solving the maximum consensus (MaxCon) problem.

SPP-Net: Deep Absolute Pose Regression with Synthetic Views

1 code implementation9 Dec 2017 Pulak Purkait, Cheng Zhao, Christopher Zach

In this work we design a deep neural network architecture based on sparse feature descriptors to estimate the absolute pose of an image.

Image-Based Localization Pose Estimation +1

Minimal Solvers for Monocular Rolling Shutter Compensation under Ackermann Motion

no code implementations8 Dec 2017 Pulak Purkait, Christopher Zach

Modern automotive vehicles are often equipped with a budget commercial rolling shutter camera.

Motion Compensation

Rolling Shutter Correction in Manhattan World

no code implementations ICCV 2017 Pulak Purkait, Christopher Zach, Ales Leonardis

A vast majority of consumer cameras operate the rolling shutter mechanism, which often produces distorted images due to inter-row delay while capturing an image.

Rolling Shutter Correction

Revisiting the Variable Projection Method for Separable Nonlinear Least Squares Problems

no code implementations CVPR 2017 Je Hyeong Hong, Christopher Zach, Andrew Fitzgibbon

Variable Projection (VarPro) is a framework to solve optimization problems efficiently by optimally eliminating a subset of the unknowns.

The Likelihood-Ratio Test and Efficient Robust Estimation

no code implementations ICCV 2015 Andrea Cohen, Christopher Zach

Robust estimation of model parameters in the presence of outliers is a key problem in computer vision.

A Dynamic Programming Approach for Fast and Robust Object Pose Recognition From Range Images

no code implementations CVPR 2015 Christopher Zach, Adrian Penate-Sanchez, Minh-Tri Pham

Joint object recognition and pose estimation solely from range images is an important task e. g. in robotics applications and in automated manufacturing environments.

Object Recognition Pose Estimation

A Principled Approach for Coarse-to-Fine MAP Inference

no code implementations CVPR 2014 Christopher Zach

In this work we reconsider labeling problems with (virtually) continuous state spaces, which are of relevance in low level computer vision.

Compact Relaxations for MAP Inference in Pairwise MRFs with Piecewise Linear Priors

no code implementations14 Aug 2013 Christopher Zach, Christian Häne

The number of unknowns is O(LK) per pairwise clique in terms of the state space size $L$ and the number of linear segments K. This compares to an O(L^2) size complexity of the standard LP relaxation if the piecewise linear structure is ignored.

Joint 3D Scene Reconstruction and Class Segmentation

no code implementations CVPR 2013 Christian Hane, Christopher Zach, Andrea Cohen, Roland Angst, Marc Pollefeys

Image segmentations provide geometric cues about which surface orientations are more likely to appear at a certain location in space whereas a dense 3D reconstruction yields a suitable regularization for the segmentation problem by lifting the labeling from 2D images to 3D space.

3D Reconstruction 3D Scene Reconstruction +3

Gated Softmax Classification

no code implementations NeurIPS 2010 Roland Memisevic, Christopher Zach, Marc Pollefeys, Geoffrey E. Hinton

We describe a log-bilinear" model that computes class probabilities by combining an input vector multiplicatively with a vector of binary latent variables.

Classification General Classification

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