1,382 research outputs found
Novel geometric features for off-line writer identification
Writer identification is an important field in forensic document examination. Typically, a writer identification system consists of two main steps: feature extraction and matching and the performance depends significantly on the feature extraction step. In this paper, we propose a set of novel geometrical features that are able to characterize different writers. These features include direction, curvature, and tortuosity. We also propose an improvement of the edge-based directional and chain code-based features. The proposed methods are applicable to Arabic and English handwriting. We have also studied several methods for computing the distance between feature vectors when comparing two writers. Evaluation of the methods is performed using both the IAM handwriting database and the QUWI database for each individual feature reaching Top1 identification rates of 82 and 87 % in those two datasets, respectively. The accuracies achieved by Kernel Discriminant Analysis (KDA) are significantly higher than those observed before feature-level writer identification was implemented. The results demonstrate the effectiveness of the improved versions of both chain-code features and edge-based directional features
Novel geometric features for off-line writer identification
Writer identification is an important field in forensic document examination. Typically, a writer identification system consists of two main steps: feature extraction and matching and the performance depends significantly on the feature extraction step. In this paper, we propose a set of novel geometrical features that are able to characterize different writers. These features include direction, curvature, and tortuosity. We also propose an improvement of the edge-based directional and chain code-based features. The proposed methods are applicable to Arabic and English handwriting. We have also studied several methods for computing the distance between feature vectors when comparing two writers. Evaluation of the methods is performed using both the IAM handwriting database and the QUWI database for each individual feature reaching Top1 identification rates of 82 and 87 % in those two datasets, respectively. The accuracies achieved by Kernel Discriminant Analysis (KDA) are significantly higher than those observed before feature-level writer identification was implemented. The results demonstrate the effectiveness of the improved versions of both chain-code features and edge-based directional features.Qatar National Research Fund through the National Priority Research Program (NPRP) No. 09-864-1-128Scopu
Recognition of off-line handwritten cursive text
The author presents novel algorithms to design unconstrained handwriting
recognition systems organized in three parts:
In Part One, novel algorithms are presented for processing of Arabic text prior to
recognition. Algorithms are described to convert a thinned image of a stroke to a straight
line approximation. Novel heuristic algorithms and novel theorems are presented to
determine start and end vertices of an off-line image of a stroke. A straight line
approximation of an off-line stroke is converted to a one-dimensional representation by
a novel algorithm which aims to recover the original sequence of writing. The resulting
ordering of the stroke segments is a suitable preprocessed representation for subsequent
handwriting recognition algorithms as it helps to segment the stroke. The algorithm was
tested against one data set of isolated handwritten characters and another data set of
cursive handwriting, each provided by 20 subjects, and has been 91.9% and 91.8%
successful for these two data sets, respectively.
In Part Two, an entirely novel fuzzy set-sequential machine character recognition
system is presented. Fuzzy sequential machines are defined to work as recognizers of
handwritten strokes. An algorithm to obtain a deterministic fuzzy sequential machine from
a stroke representation, that is capable of recognizing that stroke and its variants, is
presented. An algorithm is developed to merge two fuzzy machines into one machine. The
learning algorithm is a combination of many described algorithms. The system was tested
against isolated handwritten characters provided by 20 subjects resulting in 95.8%
recognition rate which is encouraging and shows that the system is highly flexible in
dealing with shape and size variations.
In Part Three, also an entirely novel text recognition system, capable of recognizing
off-line handwritten Arabic cursive text having a high variability is presented. This system
is an extension of the above recognition system. Tokens are extracted from a onedimensional
representation of a stroke. Fuzzy sequential machines are defined to work as
recognizers of tokens. It is shown how to obtain a deterministic fuzzy sequential machine
from a token representation that is capable'of recognizing that token and its variants. An
algorithm for token learning is presented. The tokens of a stroke are re-combined to
meaningful strings of tokens. Algorithms to recognize and learn token strings are
described. The. recognition stage uses algorithms of the learning stage. The process of
extracting the best set of basic shapes which represent the best set of token strings that
constitute an unknown stroke is described. A method is developed to extract lines from
pages of handwritten text, arrange main strokes of extracted lines in the same order as
they were written, and present secondary strokes to main strokes. Presented secondary
strokes are combined with basic shapes to obtain the final characters by formulating and
solving assignment problems for this purpose. Some secondary strokes which remain
unassigned are individually manipulated. The system was tested against the handwritings
of 20 subjects yielding overall subword and character recognition rates of 55.4% and
51.1%, respectively
A novel approach for handedness detection from off-line handwriting using fuzzy conceptual reduction
Information Preserving Processing of Noisy Handwritten Document Images
Many pre-processing techniques that normalize artifacts and clean noise induce anomalies due to discretization of the document image. Important information that could be used at later stages may be lost. A proposed composite-model framework takes into account pre-printed information, user-added data, and digitization characteristics. Its benefits are demonstrated by experiments with statistically significant results. Separating pre-printed ruling lines from user-added handwriting shows how ruling lines impact people\u27s handwriting and how they can be exploited for identifying writers. Ruling line detection based on multi-line linear regression reduces the mean error of counting them from 0.10 to 0.03, 6.70 to 0.06, and 0.13 to 0.02, com- pared to an HMM-based approach on three standard test datasets, thereby reducing human correction time by 50%, 83%, and 72% on average. On 61 page images from 16 rule-form templates, the precision and recall of form cell recognition are increased by 2.7% and 3.7%, compared to a cross-matrix approach. Compensating for and exploiting ruling lines during feature extraction rather than pre-processing raises the writer identification accuracy from 61.2% to 67.7% on a 61-writer noisy Arabic dataset. Similarly, counteracting page-wise skew by subtracting it or transforming contours in a continuous coordinate system during feature extraction improves the writer identification accuracy. An implementation study of contour-hinge features reveals that utilizing the full probabilistic probability distribution function matrix improves the writer identification accuracy from 74.9% to 79.5%
Character Recognition
Character recognition is one of the pattern recognition technologies that are most widely used in practical applications. This book presents recent advances that are relevant to character recognition, from technical topics such as image processing, feature extraction or classification, to new applications including human-computer interfaces. The goal of this book is to provide a reference source for academic research and for professionals working in the character recognition field
Content Recognition and Context Modeling for Document Analysis and Retrieval
The nature and scope of available documents are changing significantly in many areas of document analysis and retrieval as complex, heterogeneous collections become accessible to virtually everyone via the web. The increasing level of diversity presents a great challenge for document image content categorization, indexing, and retrieval. Meanwhile, the processing of documents with unconstrained layouts and complex formatting often requires effective leveraging of broad contextual knowledge.
In this dissertation, we first present a novel approach for document image content categorization, using a lexicon of shape features. Each lexical word corresponds to a scale and rotation invariant local shape feature that is generic enough to be detected repeatably and is segmentation free. A concise, structurally indexed shape lexicon is learned by clustering and partitioning feature types through graph cuts. Our idea finds successful application in several challenging tasks, including content recognition of diverse web images and language identification on documents composed of mixed machine printed text and handwriting.
Second, we address two fundamental problems in signature-based document image retrieval. Facing continually increasing volumes of documents, detecting and recognizing unique, evidentiary visual entities (\eg, signatures and logos) provides a practical and reliable supplement to the OCR recognition of printed text. We propose a novel multi-scale framework to detect and segment signatures jointly from document images, based on the structural saliency under a signature production model. We formulate the problem of signature retrieval in the unconstrained setting of geometry-invariant deformable shape matching and demonstrate state-of-the-art performance in signature matching and verification.
Third, we present a model-based approach for extracting relevant named entities from unstructured documents. In a wide range of applications that require structured information from diverse, unstructured document images, processing OCR text does not give satisfactory results due to the absence of linguistic context. Our approach enables learning of inference rules collectively based on contextual information from both page layout and text features.
Finally, we demonstrate the importance of mining general web user behavior data for improving document ranking and other web search experience. The context of web user activities reveals their preferences and intents, and we emphasize the analysis of individual user sessions for creating aggregate models. We introduce a novel algorithm for estimating web page and web site importance, and discuss its theoretical foundation based on an intentional surfer model. We demonstrate that our approach significantly improves large-scale document retrieval performance
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