Tomislav Hrkac - Academia.edu (original) (raw)

Papers by Tomislav Hrkac

2015 38th International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2015

ABSTRACT We propose a solution which enables automated attribution of formative exams to students... more ABSTRACT We propose a solution which enables automated attribution of formative exams to students. We define the student identifier matrix, which is a graphical representation of a student ID number. The matrix is annotated by the student during the exam. We introduce a robust image processing procedure which enables automated recovery of the student ID from the matrix. We show that the proposed procedure achieves a recognition rate of 100% on 296 samples in presence of skewing, rotation and offsets introduced by the printing and the scanning processes.

EUROCON 2007 - The International Conference on "Computer as a Tool", 2007

Knowledge representation of time and space, and reasoning about temporal and spatial relations, a... more Knowledge representation of time and space, and reasoning about temporal and spatial relations, are important areas in fields such as visual object tracking, robot vision, multimedia, geographical information systems, etc. In this paper we present a formal model of knowledge representation and reasoning for spatio-temporal domains. The model is based on the high-level Petri nets called the Petri Nets with

Lecture Notes in Computer Science, 2007

The paper presents an approach to multimodal image registration. The method is developed for alig... more The paper presents an approach to multimodal image registration. The method is developed for aligning infrared (IR) and visual (RGB) images of facades. It is based on mapping clouds of points extracted by a corner detector applied to both images. The experiments show that corners are suitable features for our application. In the alignment process a number of transformation hypotheses is generated and evaluated. The evaluation is performed by measuring similarity between the RGB corners and the transformed corners from IR image. Directed partial Hausdorff distance is used as a robust similarity measure. The implemented system has been tested on various IR-RGB pairs of images of buildings. The results show that the method can be used for image registration, but also expose some typical problems.

Knowledge and Information Systems, 2008

... 2], formal logic of plans [38], time maps [12], metric constraints [13], timed, time and temp... more ... 2], formal logic of plans [38], time maps [12], metric constraints [13], timed, time and temporalPetri nets [9, 20, 32, 33, 49], fuzzy time Petri ... Weyns and Holvoet proposed a Colored Petri Netbased model for the space-situated agents where time is implicitly represented [55, 56]. ...

Journal of Computing and Information Technology, 2003

ABSTRACT An object-oriented implementation of a program simulator for a multiagent system (MAS) i... more ABSTRACT An object-oriented implementation of a program simulator for a multiagent system (MAS) is described. The model of a MAS is hierarchical model, consisting of different levels, where each level contains clusters of agents. A paradigm of a blackboard is used for communication among agents, clusters, as well as levels. Petri nets with time tokens are used as a basic concept for this model. An example of the use of the object-oriented simulator in a dynamic scene analysis is given.

Information Systems, 2012

In many application areas there is a need to represent human-like knowledge related to spatio-tem... more In many application areas there is a need to represent human-like knowledge related to spatio-temporal relations among multiple moving objects. This type of knowledge is usually imprecise, vague and fuzzy, while the reasoning about spatio-temporal relations is intuitive. In this paper we present a model of fuzzy spatio-temporal knowledge representation and reasoning based on high-level Petri nets. The model should be suitable for the design of a knowledge base for real-time, multi-agent-based intelligent systems that include expert or user human-like knowledge. The central part of the model is the knowledge representation scheme called FuSpaT, which supports the representation and reasoning for domains that include imprecise and fuzzy spatial, temporal and spatio-temporal relationships. The scheme is based on the high-level Petri nets called Petri nets with fuzzy spatio-temporal tokens (PeNeFuST). The FuSpaT scheme integrates the theory of the PeNeFuST and 117 spatio-temporal relations.

2014 37th International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2014

ABSTRACT Automated grading of multiple-choice exams is of great interest in university courses wi... more ABSTRACT Automated grading of multiple-choice exams is of great interest in university courses with a large number of students. We consider an existing system in which exams are automatically graded using simple answer sheets that are annotated by the student. A sheet consists of a series of circles representing possible answers. As annotation errors are possible, a student is permitted to alter the annotated answer by annotating the“error” circle and handwriting the letter of the correct answer next to the appropriate row. During the scanning process, if an annotated“error” circle is detected, the system raises an alarm and requires intervention from a human operator to determine which answer to consider valid. We propose rather simple and effecive computer vision algorithm which enables automated reading of a limited set of handwritten answers and minimizes the need for a human intervention in the scanning process. We test our algorithm on a large dataset of real scanned answer sheets, and report encouraging performance rates.

2015 38th International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2015

ABSTRACT We propose a solution which enables automated attribution of formative exams to students... more ABSTRACT We propose a solution which enables automated attribution of formative exams to students. We define the student identifier matrix, which is a graphical representation of a student ID number. The matrix is annotated by the student during the exam. We introduce a robust image processing procedure which enables automated recovery of the student ID from the matrix. We show that the proposed procedure achieves a recognition rate of 100% on 296 samples in presence of skewing, rotation and offsets introduced by the printing and the scanning processes.

EUROCON 2007 - The International Conference on "Computer as a Tool", 2007

Knowledge representation of time and space, and reasoning about temporal and spatial relations, a... more Knowledge representation of time and space, and reasoning about temporal and spatial relations, are important areas in fields such as visual object tracking, robot vision, multimedia, geographical information systems, etc. In this paper we present a formal model of knowledge representation and reasoning for spatio-temporal domains. The model is based on the high-level Petri nets called the Petri Nets with

Lecture Notes in Computer Science, 2007

The paper presents an approach to multimodal image registration. The method is developed for alig... more The paper presents an approach to multimodal image registration. The method is developed for aligning infrared (IR) and visual (RGB) images of facades. It is based on mapping clouds of points extracted by a corner detector applied to both images. The experiments show that corners are suitable features for our application. In the alignment process a number of transformation hypotheses is generated and evaluated. The evaluation is performed by measuring similarity between the RGB corners and the transformed corners from IR image. Directed partial Hausdorff distance is used as a robust similarity measure. The implemented system has been tested on various IR-RGB pairs of images of buildings. The results show that the method can be used for image registration, but also expose some typical problems.

Knowledge and Information Systems, 2008

... 2], formal logic of plans [38], time maps [12], metric constraints [13], timed, time and temp... more ... 2], formal logic of plans [38], time maps [12], metric constraints [13], timed, time and temporalPetri nets [9, 20, 32, 33, 49], fuzzy time Petri ... Weyns and Holvoet proposed a Colored Petri Netbased model for the space-situated agents where time is implicitly represented [55, 56]. ...

Journal of Computing and Information Technology, 2003

ABSTRACT An object-oriented implementation of a program simulator for a multiagent system (MAS) i... more ABSTRACT An object-oriented implementation of a program simulator for a multiagent system (MAS) is described. The model of a MAS is hierarchical model, consisting of different levels, where each level contains clusters of agents. A paradigm of a blackboard is used for communication among agents, clusters, as well as levels. Petri nets with time tokens are used as a basic concept for this model. An example of the use of the object-oriented simulator in a dynamic scene analysis is given.

Information Systems, 2012

In many application areas there is a need to represent human-like knowledge related to spatio-tem... more In many application areas there is a need to represent human-like knowledge related to spatio-temporal relations among multiple moving objects. This type of knowledge is usually imprecise, vague and fuzzy, while the reasoning about spatio-temporal relations is intuitive. In this paper we present a model of fuzzy spatio-temporal knowledge representation and reasoning based on high-level Petri nets. The model should be suitable for the design of a knowledge base for real-time, multi-agent-based intelligent systems that include expert or user human-like knowledge. The central part of the model is the knowledge representation scheme called FuSpaT, which supports the representation and reasoning for domains that include imprecise and fuzzy spatial, temporal and spatio-temporal relationships. The scheme is based on the high-level Petri nets called Petri nets with fuzzy spatio-temporal tokens (PeNeFuST). The FuSpaT scheme integrates the theory of the PeNeFuST and 117 spatio-temporal relations.

2014 37th International Convention on Information and Communication Technology, Electronics and Microelectronics (MIPRO), 2014

ABSTRACT Automated grading of multiple-choice exams is of great interest in university courses wi... more ABSTRACT Automated grading of multiple-choice exams is of great interest in university courses with a large number of students. We consider an existing system in which exams are automatically graded using simple answer sheets that are annotated by the student. A sheet consists of a series of circles representing possible answers. As annotation errors are possible, a student is permitted to alter the annotated answer by annotating the“error” circle and handwriting the letter of the correct answer next to the appropriate row. During the scanning process, if an annotated“error” circle is detected, the system raises an alarm and requires intervention from a human operator to determine which answer to consider valid. We propose rather simple and effecive computer vision algorithm which enables automated reading of a limited set of handwritten answers and minimizes the need for a human intervention in the scanning process. We test our algorithm on a large dataset of real scanned answer sheets, and report encouraging performance rates.