2,797 research outputs found
Continuous Multiclass Labeling Approaches and Algorithms
We study convex relaxations of the image labeling problem on a continuous
domain with regularizers based on metric interaction potentials. The generic
framework ensures existence of minimizers and covers a wide range of
relaxations of the originally combinatorial problem. We focus on two specific
relaxations that differ in flexibility and simplicity -- one can be used to
tightly relax any metric interaction potential, while the other one only covers
Euclidean metrics but requires less computational effort. For solving the
nonsmooth discretized problem, we propose a globally convergent
Douglas-Rachford scheme, and show that a sequence of dual iterates can be
recovered in order to provide a posteriori optimality bounds. In a quantitative
comparison to two other first-order methods, the approach shows competitive
performance on synthetical and real-world images. By combining the method with
an improved binarization technique for nonstandard potentials, we were able to
routinely recover discrete solutions within 1%--5% of the global optimum for
the combinatorial image labeling problem
HopSkipJumpAttack: A Query-Efficient Decision-Based Attack
The goal of a decision-based adversarial attack on a trained model is to
generate adversarial examples based solely on observing output labels returned
by the targeted model. We develop HopSkipJumpAttack, a family of algorithms
based on a novel estimate of the gradient direction using binary information at
the decision boundary. The proposed family includes both untargeted and
targeted attacks optimized for and similarity metrics
respectively. Theoretical analysis is provided for the proposed algorithms and
the gradient direction estimate. Experiments show HopSkipJumpAttack requires
significantly fewer model queries than Boundary Attack. It also achieves
competitive performance in attacking several widely-used defense mechanisms.
(HopSkipJumpAttack was named Boundary Attack++ in a previous version of the
preprint.
Paradigm of tunable clustering using binarization of consensus partition matrices (Bi-CoPaM) for gene discovery
Copyright @ 2013 Abu-Jamous et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Clustering analysis has a growing role in the study of co-expressed genes for gene discovery. Conventional binary and fuzzy clustering do not embrace the biological reality that some genes may be irrelevant for a problem and not be assigned to a cluster, while other genes may participate in several biological functions and should simultaneously belong to multiple clusters. Also, these algorithms cannot generate tight clusters that focus on their cores or wide clusters that overlap and contain all possibly relevant genes. In this paper, a new clustering paradigm is proposed. In this paradigm, all three eventualities of a gene being exclusively assigned to a single cluster, being assigned to multiple clusters, and being not assigned to any cluster are possible. These possibilities are realised through the primary novelty of the introduction of tunable binarization techniques. Results from multiple clustering experiments are aggregated to generate one fuzzy consensus partition matrix (CoPaM), which is then binarized to obtain the final binary partitions. This is referred to as Binarization of Consensus Partition Matrices (Bi-CoPaM). The method has been tested with a set of synthetic datasets and a set of five real yeast cell-cycle datasets. The results demonstrate its validity in generating relevant tight, wide, and complementary clusters that can meet requirements of different gene discovery studies.National Institute for Health Researc
Empirical Study of Car License Plates Recognition
The number of vehicles on the road has increased drastically in recent years. The license plate is an identity card for a vehicle. It can map to the owner and further information about vehicle. License plate information is useful to help traffic management systems. For example, traffic management systems can check for vehicles moving at speeds not permitted by law and can also be installed in parking areas to se-cure the entrance or exit way for vehicles. License plate recognition algorithms have been proposed by many researchers. License plate recognition requires license plate detection, segmentation, and charac-ters recognition. The algorithm detects the position of a license plate and extracts the characters. Various license plate recognition algorithms have been implemented, and each algorithm has its strengths and weaknesses. In this research, I implement three algorithms for detecting license plates, three algorithms for segmenting license plates, and two algorithms for recognizing license plate characters. I evaluate each of these algorithms on the same two datasets, one from Greece and one from Thailand. For detecting li-cense plates, the best result is obtained by a Haar cascade algorithm. After the best result of license plate detection is obtained, for the segmentation part a Laplacian based method has the highest accuracy. Last, the license plate recognition experiment shows that a neural network has better accuracy than other algo-rithm. I summarize and analyze the overall performance of each method for comparison
Optimization of Image Processing Algorithms for Character Recognition in Cultural Typewritten Documents
Linked Data is used in various fields as a new way of structuring and
connecting data. Cultural heritage institutions have been using linked data to
improve archival descriptions and facilitate the discovery of information. Most
archival records have digital representations of physical artifacts in the form
of scanned images that are non-machine-readable. Optical Character Recognition
(OCR) recognizes text in images and translates it into machine-encoded text.
This paper evaluates the impact of image processing methods and parameter
tuning in OCR applied to typewritten cultural heritage documents. The approach
uses a multi-objective problem formulation to minimize Levenshtein edit
distance and maximize the number of words correctly identified with a
non-dominated sorting genetic algorithm (NSGA-II) to tune the methods'
parameters. Evaluation results show that parameterization by digital
representation typology benefits the performance of image pre-processing
algorithms in OCR. Furthermore, our findings suggest that employing image
pre-processing algorithms in OCR might be more suitable for typologies where
the text recognition task without pre-processing does not produce good results.
In particular, Adaptive Thresholding, Bilateral Filter, and Opening are the
best-performing algorithms for the theatre plays' covers, letters, and overall
dataset, respectively, and should be applied before OCR to improve its
performance.Comment: 25 pages, 4 figure
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