8 research outputs found
Tight and simple Web graph compression
Analysing Web graphs has applications in determining page ranks, fighting Web
spam, detecting communities and mirror sites, and more. This study is however
hampered by the necessity of storing a major part of huge graphs in the
external memory, which prevents efficient random access to edge (hyperlink)
lists. A number of algorithms involving compression techniques have thus been
presented, to represent Web graphs succinctly but also providing random access.
Those techniques are usually based on differential encodings of the adjacency
lists, finding repeating nodes or node regions in the successive lists, more
general grammar-based transformations or 2-dimensional representations of the
binary matrix of the graph. In this paper we present two Web graph compression
algorithms. The first can be seen as engineering of the Boldi and Vigna (2004)
method. We extend the notion of similarity between link lists, and use a more
compact encoding of residuals. The algorithm works on blocks of varying size
(in the number of input lines) and sacrifices access time for better
compression ratio, achieving more succinct graph representation than other
algorithms reported in the literature. The second algorithm works on blocks of
the same size, in the number of input lines, and its key mechanism is merging
the block into a single ordered list. This method achieves much more attractive
space-time tradeoffs.Comment: 15 page
Analiza wymaga艅 dla systemu elektronicznego oceniania rozwi膮za艅 zada艅 egzaminacyjnych
Tyt. z nag艂贸wka.Bibliogr. s. 1405.Dost臋pny r贸wnie偶 w formie drukowanej.STRESZCZENIE: W artykule zaprezentowano ide臋 e-oceniania, czyli systemu umo偶liwiaj膮cego sprawdzanie prac egzaminacyjnych przez egzaminatora na ekranie monitora oraz automatyczne sprawdzanie prac przez system inteligentny. Nietrywialnym problemem jest analiza rozwi膮za艅 zada艅 otwartych, czyli takich, w kt贸rych samodzielnie formu艂uje si臋 i zapisuje odpowiedzi. W niniejszym artykule zostanie zaprezentowany projekt architektury systemu rozproszonego, kt贸ry b臋dzie skanowa艂 rozwi膮zania zada艅 i obs艂ugiwa艂 rozdzielenie prac na zespo艂y oraz kierowanie procesem oceniania w spos贸b bezpieczny i wydajny. Docelowo system ma by膰 wykorzystany przez Centraln膮 Komisj臋 Egzaminacyjn膮 do przeprowadzania egzamin贸w w gimnazjach oraz egzamin贸w maturalnych. S艁OWA KLUCZOWE: E-ocenianie, in偶ynieria oprogramowania. ABSTRACT: In his paper the idea of e-evaluation is presented. This is a system for checking sheets of paper in the examination by the examiner directly on the computer screen. The advantage of such a solution is, as experience has shown, to improve the quality of the preparation of the test and its evaluation. The process of automation of the examination includes systems of electronic tests, commonly implemented both as a standalone or distributed application. We present the project architecture of a web system for scanning exam sheets, distributing the scans to examiners and managing the whole process of examination in a secure and effective way. A long-term goal is to let Central Examination Board deploy the system in maturity and high school examinations. KEYWORDS: E-evaluation, software engineering
Analiza wymaga艅 dla metod przetwarzania wst臋pnego obraz贸w w automatycznym rozpoznawaniu tekstu
Tyt. z nag艂贸wka.Bibliografia s. 532.Dost臋pny r贸wnie偶 w formie drukowanej.ABSTRACT: The paper presents a survey over image processing algorithms for automatic optical text recognition. We point on image preprocessing techniques which are responsible for image defects as well as acquisition errors suppression. Image distortion depends not only on the device type and its operating conditions but also on image file format. The aim of the experimental part was to test the recognition ability of FineReader sofrware on a test text page. STRESZCZENIE: W artykule przedstawiono przegl膮d zagadnie艅 dotycz膮cych algorytm贸w przetwarzania obraz贸w dla potrzeb automatycznego rozpoznawania tekstu. Uwag臋 skupiono na algorytmach przetwarzania wst臋pnego, kt贸rych celem jest usuni臋cie b艂臋d贸w akwizycji obrazu oraz defekt贸w samego obrazu. B艂臋dy te uzale偶nione s膮 od typu samego urz膮dzenia, warunk贸w jego pracy, a tak偶e zastosowanego formatu zapisu pliku obrazu. Cz臋艣膰 do艣wiadczalna pracy polega艂a na przetestowaniu zdolno艣ci rozpoznawania strony tekstu programem FineReader. S艁OWA KLUCZOWE: przetwarzanie obraz贸w, rozpoznawanie obraz贸w
Fine-tuned spot detection on ELISPOT images
Tyt. z nag艂贸wka.Bibliografia s.791.Dost臋pny r贸wnie偶 w formie drukowanej.ABSTRACT: Enzyme linked immunospot assay (ELISPOT) is a powerful technique used for detection and quantification of antigen specific immunological responses at the single cell level, which could have a prognostic value to diagnose the long-term graft outcome (i.e., kidney) and to evaluate the level of immunosuppression therapy needed. Basically, ELISPOT image contains round spots of different color, intensity and size. The image analysis should include accurate measurements of spot properties, like area and color. We propose a new approach to spot detection and measurement on ELISPOT microscope images, combining the Canny operator and a circle-fitting routine that we previously used (in somewhat different context) for that class of images. Good edge detection algorithms, like the Canny one, yield locally accurate spot contour arcs but their drawback is that the found arcs are not connected, i.e., do not constitute full contours. We solved the problem, fitting arcs belonging to the same spot contour. For each arc, a circle to each it belongs was approximated and then circle clus-tering was performed not to produce too many (false) contours. STRESZCZENIE: ELISPOT (enzyme linked immunospot assay) jest metod膮 pozwalaj膮c膮 na ocen臋 nat臋偶enia odpowiedzi immunologicznej wobec okre艣lonych antygen贸w na poziomie pojedynczych kom贸rek. Badanie tej odpowiedzi pozwala na monitorowanie ryzyka przewlek艂ego odrzutu przeszczepu (np. nerki) i zastosowania odpowiedniej terapii immunosupresyjnej. Obraz w badaniu ELISPOT zawiera okr膮g艂e plamki r贸偶ni膮ce si臋 zabarwieniem, wielko艣ci膮 i intensywno艣ci膮. Celem analizy komputerowej obrazu jest precyzyjny pomiar parametr贸w plamek, takich jak pole powierzchni i kolor. W pracy zaproponowano nowy algorytm detekcji i okre艣lenia kontur贸w plamek 艂膮cz膮cy operator Canny'ego z procedur膮 aproksymacji 艣redniokwadratowej okr臋giem konturu. Podobna metoda zosta艂a przez nas sprawdzona w innym kontek艣cie (wykrywanie ca艂kowitego obszaru zainteresowania). Algorytmy detekcji kraw臋dzi (m.in. Canny) dobrze lokalnie oddaj膮 fragmenty rozmytych kontur贸w, ale zwykle zwracaj膮 艂uki, a nie zamkni臋te krzywe. Rozwi膮zali艣my ten problem, dopasowuj膮c do siebie 艂uki nale偶膮ce do tego samego konturu. Dla ka偶dego 艂uku znajdowane by艂o ko艂o, a nast臋pnie w procesie grupowania usuwali艣my fa艂szywe (nadmiarowe) kontury. KEYWORDS: ELISPOT, Canny's operator, color images. S艁OWA KLUCZOWE: ELISPOT, operator Canny 'ego, obrazy barwne
Computer aided evaluation of selected examination tasks in mathematics using generalized Hough transform
In this chapter an image processing algorithm for automatic evaluation of
scanned examination sheets is described. The discussed image contains selected
geometric figures drawn by hand on a printed coordinate system. This
type of task is characteristic of final high school exams of natural sciences.
Our challenge was to develop an evaluation algorithm, which works with
a precision comparable to the teacher. If the image contains the correct solution,
the algorithm should husk it from a set of random lines, deletions,
amendments, drafts, bearing in mind, that lines were drawn by hand. In addition,
the algorithm should calculate scores for partially correct solutions.
An essential part of our proposal is based on Hough transform (for recognizing
lines) and generalized Hough transform (for recognizing non linear
shapes). The proposed solution is flexible and can be extended to other types
of tasks such as drawing geometrical figures.[...
A TWO-PASS MEDIAN-LIKE FILTER FOR IMPULSE NOISE REMOVAL IN MULTI-CHANNEL IMAGES
We propose a two-pass median filter for impulse noise suppression in color images. The first pass is our previously presented algorithm, PNN-VMF [2]. The second pass routine is chosen dynamically on the basis of the number of pixel modifications performed by the first pass filtering. Such an approach is likely to avoid harm (e.g., blurring edges) resulting from excessive filtering. The effectiveness of the algorithm has been experimentally verified on 15 standard images. 1