共查询到20条相似文献,搜索用时 11 毫秒
1.
John F. Pitrelli Amit Roy 《International Journal on Document Analysis and Recognition》2003,5(2-3):126-137
We discuss development of a word-unigram language model for online handwriting recognition. First, we tokenize a text corpus
into words, contrasting with tokenization methods designed for other purposes. Second, we select for our model a subset of
the words found, discussing deviations from an N-most-frequent-words approach. From a 600-million-word corpus, we generated a 53,000-word model which eliminates 45% of word-recognition
errors made by a character-level-model baseline system. We anticipate that our methods will be applicable to offline recognition
as well, and to some extent to other recognizers, such as speech recognizers and video retrieval systems.
Received: November 1, 2001 / Revised version: July 22, 2002 相似文献
2.
Giovanni Seni John Seybold 《International Journal on Document Analysis and Recognition》1999,2(1):24-29
Out-of-order diacriticals introduce significant complexity to the design of an online handwriting recognizer, because they
require some reordering of the time domain information. It is common in cursive writing to write the body of an `i' or `t'
during the writing of the word, and then to return and dot or cross the letter once the word is complete. The difficulty arises
because we have to look ahead, when scoring one of these letters, to find the mark occurring later in the writing stream that
completes the letter. We should also remember that we have used this mark, so that we don't use it again for a different letter,
and we should also penalize a word if there are some marks that look like diacriticals that are not used. One approach to
this problem is to scan the writing some distance into the future to identify candidate diacriticals, remove them in a preprocessing
step, and associate them with the matching letters earlier in the word. If done as a preliminary operation, this approach
is error-prone: marks that are not diacriticals may be incorrectly identified and removed, and true diacriticals may be skipped.
This paper describes a novel extension to a forward search algorithm that provides a natural mechanism for considering alternative
treatments of potential diacriticals, to see whether it is better to treat a given mark as a diacritical or not, and directly
compare the two outcomes by score.
Received October 30, 1998 / Revised January 25, 1999 相似文献
3.
S. Jaeger S. Manke J. Reichert A. Waibel 《International Journal on Document Analysis and Recognition》2001,3(3):169-180
This paper presents the online handwriting recognition system NPen++ developed at the University of Karlsruhe and Carnegie
Mellon University. The NPen++ recognition engine is based on a multi-state time delay neural network and yields recognition
rates from 96% for a 5,000 word dictionary to 93.4% on a 20,000 word dictionary and 91.2% for a 50,000 word dictionary. The
proposed tree search and pruning technique reduces the search space considerably without losing too much recognition performance
compared to an exhaustive search. This enables the NPen++ recognizer to be run in real-time with large dictionaries. Initial
recognition rates for whole sentences are promising and show that the MS-TDNN architecture is suited to recognizing handwritten
data ranging from single characters to whole sentences.
Received September 3, 2000 / Revised October 9, 2000 相似文献
4.
E. Kavallieratou N. Fakotakis G. Kokkinakis 《International Journal on Document Analysis and Recognition》2002,4(4):226-242
In this paper, an integrated offline recognition system for unconstrained handwriting is presented. The proposed system consists
of seven main modules: skew angle estimation and correction, printed-handwritten text discrimination, line segmentation, slant
removing, word segmentation, and character segmentation and recognition, stemming from the implementation of already existing
algorithms as well as novel algorithms. This system has been tested on the NIST, IAM-DB, and GRUHD databases and has achieved
accuracy that varies from 65.6% to 100% depending on the database and the experiment. 相似文献
5.
M. Kobayashi S. Masaki O. Miyamoto Y. Nakagawa Y. Komiya T. Matsumoto 《International Journal on Document Analysis and Recognition》2001,3(3):181-191
A new algorithm RAV (reparameterized angle variations) is proposed which makes explicit use of trajectory information where the time evolution of the pen coordinates plays a crucial role. The algorithm is robust against stroke connections/abbreviations
as well as shape distortions, while maintaining reasonable robustness against stroke-order variations. Preliminary experiments
are reported on tests against the Kuchibue_d-96-02 database from the Tokyo University of Agriculture and Technology.
Received July 24, 2000 / Revised October 6, 2000 相似文献
6.
Gyeonghwan Kim Venu Govindaraju Sargur N. Srihari 《International Journal on Document Analysis and Recognition》1999,2(1):37-44
This paper presents an end-to-end system for reading handwritten page images. Five functional modules included in the system
are introduced in this paper: (i) pre-processing, which concerns introducing an image representation for easy manipulation
of large page images and image handling procedures using the image representation; (ii) line separation, concerning text line
detection and extracting images of lines of text from a page image; (iii) word segmentation, which concerns locating word
gaps and isolating words from a line of text image obtained efficiently and in an intelligent manner; (iv) word recognition,
concerning handwritten word recognition algorithms; and (v) linguistic post-pro- cessing, which concerns the use of linguistic
constraints to intelligently parse and recognize text. Key ideas employed in each functional module, which have been developed
for dealing with the diversity of handwriting in its various aspects with a goal of system reliability and robustness, are
described in this paper. Preliminary experiments show promising results in terms of speed and accuracy.
Received October 30, 1998 / Revised January 15, 1999 相似文献
7.
V. Vuori J. Laaksonen E. Oja J. Kangas 《International Journal on Document Analysis and Recognition》2001,3(3):150-159
This paper describes an adaptive recognition system for isolated handwritten characters and the experiments carried out with
it. The characters used in our experiments are alphanumeric characters, including both the upper- and lower-case versions
of the Latin alphabets and three Scandinavian diacriticals. The writers are allowed to use their own natural style of writing.
The recognition system is based on the k-nearest neighbor rule. The six character similarity measures applied by the system are all based on dynamic time warping.
The aim of the first experiments is to choose the best combination of the simple preprocessing and normalization operations
and the dissimilarity measure for a multi-writer system. However, the main focus of the work is on online adaptation. The
purpose of the adaptations is to turn a writer-independent system into writer-dependent and increase recognition performance.
The adaptation is carried out by modifying the prototype set of the classifier according to its recognition performance and
the user's writing style. The ways of adaptation include: (1) adding new prototypes; (2) inactivating confusing prototypes;
and (3) reshaping existing prototypes. The reshaping algorithm is based on the Learning Vector Quantization. Four different
adaptation strategies, according to which the modifications of the prototype set are performed, have been studied both offline
and online. Adaptation is carried out in a self-supervised fashion during normal use and thus remains unnoticed by the user.
Received June 30, 1999 / Revised September 29, 2000 相似文献
8.
Segmentation and recognition of Chinese bank check amounts 总被引:1,自引:0,他引:1
M.L. Yu P.C.K. Kwok C.H. Leung K.W. Tse 《International Journal on Document Analysis and Recognition》2001,3(4):207-217
This paper describes a system for the recognition of legal amounts on bank checks written in the Chinese language. It consists
of subsystems that perform preprocessing, segmentation, and recognition of the legal amount. In each step of the segmentation
and recognition phases, a list of possible choices are obtained. An approach is adopted whereby a large number of choices
can be processed effectively and efficiently in order to achieve the best recognition result. The contribution of this paper
is the proposal of a grammar checker for Chinese bank check amounts. It is found to be very effective in reducing the substitution
error rate. The recognition rate of the system is 74.0%, the error rate is 10.4%, and the reliability is 87.7%.
Received June 9, 2000 / Revised January 10, 2001 相似文献
9.
Algebraic query optimisation for database programming languages 总被引:1,自引:0,他引:1
Alexandra Poulovassilis Carol Small 《The VLDB Journal The International Journal on Very Large Data Bases》1996,5(2):119-132
A major challenge still facing the designers and implementors of database
programming languages (DBPLs) is that of query optimisation. We investigate
algebraic query optimisation techniques for DBPLs in the context of a purely
declarative functional language that supports sets as first-class objects.
Since the language is computationally complete issues such as
non-termination of expressions and construction of infinite data structures
can be investigated, whilst its declarative nature allows the issue of side
effects to be avoided and a richer set of equivalences to be developed.
The language has a well-defined semantics which permits us to reason
formally about the properties of expressions, such as their equivalence with
other expressions and their termination. The support of a set bulk data
type enables much prior work on the optimisation of relational languages to
be utilised.
In the paper we first give the syntax of our archetypal DBPL and briefly
discuss its semantics. We then define a small but powerful algebra of
operators over the set data type, provide some key equivalences for
expressions in these operators, and list transformation principles for
optimising expressions. Along the way, we identify some caveats to
well-known equivalences for non-deductive database languages. We next
extend our language with two higher level constructs commonly found in
functional DBPLs: set comprehensions and functions with known inverses. Some
key equivalences for these constructs are provided, as are transformation
principles for expressions in them. Finally, we investigate extending our
equivalences for the set operators to the analogous operators over bags.
Although developed and formally proved in the context of a functional
language, our findings are directly applicable to other DBPLs of similar
expressiveness.
Edited by
Matthias Jarke, Jorge Bocca, Carlo Zaniolo. Received
September 15, 1994 / Accepted September 1, 1995 相似文献
10.
Navin Kabra David J. DeWitt 《The VLDB Journal The International Journal on Very Large Data Bases》1999,8(1):55-78
In this paper we describe the design and implementation of OPT++, a tool for extensible database query optimization that
uses an object-oriented design to simplify the task of implementing, extending, and modifying an optimizer. Building an optimizer
using OPT++ makes it easy to extend the query algebra (to add new query algebra operators and physical implementation algorithms
to the system), easy to change the search space, and also to change the search strategy. Furthermore, OPT++ comes equipped
with a number of search strategies that are available for use by an optimizer-implementor. OPT++ considerably simplifies both,
the task of implementing an optimizer for a new database system, and the task of evaluating alternative optimization techniques
and strategies to decide what techniques are best suited for that database system. We present the results of a series of performance
studies. These results validate our design and show that, in spite of its flexibility, OPT++ can be used to build efficient
optimizers.
Received October 1996 / Accepted January 1998 相似文献
11.
John F. Pitrelli Jayashree Subrahmonia Michael P. Perrone 《International Journal on Document Analysis and Recognition》2006,8(1):35-46
Confidence scoring can assist in determining how to use imperfect handwriting-recognition output. We explore a confidence-scoring framework for post-processing recognition for two purposes: deciding when to reject the recognizer's output, and detecting when to change recognition parameters e.g., to relax a word-set constraint. Varied confidence scores, including likelihood ratios and posterior probabilities, are applied to an Hidden-Markov-Model (HMM) based on-line recognizer. Receiver-operating characteristic curves reveal that we successfully reject 90% of word recognition errors while rejecting only 33% of correctly-recognized words. For isolated digit recognition, we achieve 90% correct rejection while limiting false rejection to 13%. 相似文献
12.
Abstract. We propose a new adaptive strategy for text recognition that attempts to derive knowledge about the dominant font on a given
page. The strategy uses a linguistic observation that over half of all words in a typical English passage are contained in
a small set of less than 150 stop words. A small dictionary of such words is compiled from the Brown corpus. An arbitrary
text page first goes through layout analysis that produces word segmentation. A fast procedure is then applied to locate the
most likely candidates for those words, using only widths of the word images. The identity of each word is determined using
a word shape classifier. Using the word images together with their identities, character prototypes can be extracted using
a previously proposed method. We describe experiments using simulated and real images. In an experiment using 400 real page
images, we show that on average, eight distinct characters can be learned from each page, and the method is successful on
90% of all the pages. These can serve as useful seeds to bootstrap font learning.
Received October 8, 1999 / Revised March 29, 2000 相似文献
13.
14.
Mathematical expression recognition: a survey 总被引:15,自引:0,他引:15
Kam-Fai Chan Dit-Yan Yeung 《International Journal on Document Analysis and Recognition》2000,3(1):3-15
Abstract. Automatic recognition of mathematical expressions is one of the key vehicles in the drive towards transcribing documents
in scientific and engineering disciplines into electronic form. This problem typically consists of two major stages, namely,
symbol recognition and structural analysis. In this survey paper, we will review most of the existing work with respect to
each of the two major stages of the recognition process. In particular, we try to put emphasis on the similarities and differences
between systems. Moreover, some important issues in mathematical expression recognition will be addressed in depth. All these
together serve to provide a clear overall picture of how this research area has been developed to date.
Received February 22, 2000 / Revised June 12, 2000 相似文献
15.
During the last forty years, Human Handwriting Processing (HHP) has most often been investigated under the frameworks of
character (OCR) and pattern recognition. In recent years considerable progress has been made, and to date HHP can be viewed
much more as an automatic Handwriting Reading (HR) task for the machine. In this paper we propose the use of handwriting invariants,
a physical model for a first segmentation, a logical model for segmentation and recognition, a fundamental equation of handwriting,
and to integrate several sources of perception and of knowledge in order to design Handwriting Reading Systems (HRS), which
would be more universal systems than is currently the case.
At the dawn of the 3rd millennium, we guess that HHP will be considered more as a perceptual and interpretation task requiring
knowledge gained from studies on human language. This paper gives some guidelines and presents examples to design systems
able to perceive and interpret, i.e., read, handwriting automatically.
Received October 30, 1998 / Revised January 30, 1999 相似文献
16.
Sonia Garcia-Salicetti Bernadette Dorizzi Patrick Gallinari Zsolt Wimmer 《International Journal on Document Analysis and Recognition》2001,4(1):56-68
In this paper, we present a hybrid online handwriting recognition system based on hidden Markov models (HMMs). It is devoted
to word recognition using large vocabularies. An adaptive segmentation of words into letters is integrated with recognition,
and is at the heart of the training phase. A word-model is a left-right HMM in which each state is a predictive multilayer
perceptron that performs local regression on the drawing (i.e., the written word) relying on a context of observations. A
discriminative training paradigm related to maximum mutual information is used, and its potential is shown on a database of
9,781 words.
Received June 19, 2000 / Revised October 16, 2000 相似文献
17.
Cheng-Lin Liu Hiroshi Sako Hiromichi Fujisawa 《International Journal on Document Analysis and Recognition》2002,4(3):191-204
This paper describes a performance evaluation study in which some efficient classifiers are tested in handwritten digit recognition.
The evaluated classifiers include a statistical classifier (modified quadratic discriminant function, MQDF), three neural
classifiers, and an LVQ (learning vector quantization) classifier. They are efficient in that high accuracies can be achieved
at moderate memory space and computation cost. The performance is measured in terms of classification accuracy, sensitivity
to training sample size, ambiguity rejection, and outlier resistance. The outlier resistance of neural classifiers is enhanced
by training with synthesized outlier data. The classifiers are tested on a large data set extracted from NIST SD19. As results,
the test accuracies of the evaluated classifiers are comparable to or higher than those of the nearest neighbor (1-NN) rule
and regularized discriminant analysis (RDA). It is shown that neural classifiers are more susceptible to small sample size
than MQDF, although they yield higher accuracies on large sample size. As a neural classifier, the polynomial classifier (PC)
gives the highest accuracy and performs best in ambiguity rejection. On the other hand, MQDF is superior in outlier rejection
even though it is not trained with outlier data. The results indicate that pattern classifiers have complementary advantages
and they should be appropriately combined to achieve higher performance.
Received: July 18, 2001 / Accepted: September 28, 2001 相似文献
18.
Bir Bhanu Yingqiang Lin Grinnell Jones Jing Peng 《Machine Vision and Applications》2000,11(6):289-299
Target recognition is a multilevel process requiring a sequence of algorithms at low, intermediate and high levels. Generally,
such systems are open loop with no feedback between levels and assuring their performance at the given probability of correct
identification (PCI) and probability of false alarm (Pf) is a key challenge in computer vision and pattern recognition research. In this paper, a robust closed-loop system for recognition
of SAR images based on reinforcement learning is presented. The parameters in model-based SAR target recognition are learned.
The method meets performance specifications by using PCI and Pf as feedback for the learning system. It has been experimentally validated by learning the parameters of the recognition system
for SAR imagery, successfully recognizing articulated targets, targets of different configuration and targets at different
depression angles. 相似文献
19.
PicoDBMS: Scaling down database techniques for the smartcard 总被引:1,自引:0,他引:1
Philippe Pucheral Luc Bouganim Patrick Valduriez Christophe Bobineau 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(2-3):120-132
Smartcards are the most secure portable computing device today. They have been used successfully in applications involving
money, and proprietary and personal data (such as banking, healthcare, insurance, etc.). As smartcards get more powerful (with
32-bit CPU and more than 1 MB of stable memory in the next versions) and become multi-application, the need for database management
arises. However, smartcards have severe hardware limitations (very slow write, very little RAM, constrained stable memory,
no autonomy, etc.) which make traditional database technology irrelevant. The major problem is scaling down database techniques
so they perform well under these limitations. In this paper, we give an in-depth analysis of this problem and propose a PicoDBMS
solution based on highly compact data structures, query execution without RAM, and specific techniques for atomicity and durability.
We show the effectiveness of our techniques through performance evaluation.
Received: 15 October 2000 / Accepted: 15 April 2001 Published online: 23 July 2001 相似文献
20.
A model-driven approach for real-time road recognition 总被引:6,自引:0,他引:6
This article describes a method designed to detect and track road edges starting from images provided by an on-board monocular
monochromic camera. Its implementation on specific hardware is also presented in the framework of the VELAC project. The method
is based on four modules: (1) detection of the road edges in the image by a model-driven algorithm, which uses a statistical
model of the lane sides which manages the occlusions or imperfections of the road marking – this model is initialized by an
off-line training step; (2) localization of the vehicle in the lane in which it is travelling; (3) tracking to define a new
search space of road edges for the next image; and (4) management of the lane numbers to determine the lane in which the vehicle
is travelling. The algorithm is implemented in order to validate the method in a real-time context. Results obtained on marked
and unmarked road images show the robustness and precision of the method.
Received: 18 November 2000 / Accepted: 7 May 2001 相似文献