| 1. |
- Boström, Henrik
(författare)
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Forests of probability estimation trees
- 2012
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Ingår i: International journal of pattern recognition and artificial intelligence. - : World Scientific Publishing Co.. - 0218-0014. ; 26:2, s. 1251001-
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Tidskriftsartikel (refereegranskat)abstract
- Probability estimation trees (PETs) generalize classification trees in that they assign class probability distributions instead of class labels to examples that are to be classified. This property has been demonstrated to allow PETs to outperform classification trees with respect to ranking performance, as measured by the area under the ROC curve (AUC). It has further been shown that the use of probability correction improves the performance of PETs. This has lead to the use of probability correction also in forests of PETs. However, it was recently observed that probability correction may in fact deteriorate performance of forests of PETs. A more detailed study of the phenomenon is presented and the reasons behind this observation are analyzed. An empirical investigation is presented, comparing forests of classification trees to forests of both corrected and uncorrected PETS on 34 data sets from the UCI repository. The experiment shows that a small forest (10 trees) of probability corrected PETs gives a higher AUC than a similar-sized forest of classification trees, hence providing evidence in favor of using forests of probability corrected PETs. However, the picture changes when increasing the forest size, as the AUC is no longer improved by probability correction. For accuracy and squared error of predicted class probabilities (Brier score), probability correction even leads to a negative effect. An analysis of the mean squared error of the trees in the forests and their variance, shows that although probability correction results in trees that are more correct on average, the variance is reduced at the same time, leading to an overall loss of performance for larger forests. The main conclusions are that probability correction should only be employed in small forests of PETs, and that for larger forests, classification trees and PETs are equally good alternatives.
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| 2. |
- Bårman, Håkan, et al.
(författare)
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Feature Extraction for Computer-Aided Analysis of Mammograms
- 1993
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Ingår i: International journal of pattern recognition and artificial intelligence. - 0218-0014. ; 7:6, s. 1339-1356
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Tidskriftsartikel (refereegranskat)abstract
- A framework for computer-aided analysis of mammograms is described. General computer vision algorithms are combined with application specific procedures in a hierarchical fashion. The system is under development and is currently limited to detection of a few types of suspicious areas. The image features are extracted by using feature extraction methods where wavelet techniques are utilized. A low-pass pyramid representation of the image is convolved with a number of quadrature filters. The filter outputs are combined according to simple local Fourier domain models into parameters describing the local neighborhood with respect to the model. This produces estimates for each pixel describing local size, orientation, Fourier phase, and shape with confidence measures associated to each parameter. Tentative object descriptions are then extracted from the pixel-based features by application-specific procedures with knowledge of relevant structures in mammograms. The orientation, relative brightness and shape of the object are obtained by selection of the pixel feature estimates which best describe the object. The list of object descriptions is examined by procedures, where each procedure corresponds to a specific type of suspicious area, e.g. clusters of microcalcifications.
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| 3. |
- Johansson, Thomas, et al.
(författare)
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Data parallel supervised classification algorithms on multispectral images
- 1996
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Ingår i: International journal of pattern recognition and artificial intelligence. - : WORLD SCIENTIFIC PUBL CO PTE LTD. - 0218-0014. ; 10:7, s. 751-767
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Tidskriftsartikel (refereegranskat)abstract
- In remote sensing the intensities from a multispectral image are used in a classification scheme to distinguish different ground cover from each other. An example is given where different soil types are classified. A digitized complete scene from a satell
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| 4. |
- Nordberg, Klas, et al.
(författare)
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A flexible runtime system for image processing in a distributed computational environment for an unmanned aerial vehicle
- 2006
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Ingår i: International Journal of Pattern Recognition and Artificial Intelligence. - 0218-0014. ; 20:5, s. 763-780
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Tidskriftsartikel (refereegranskat)abstract
- A runtime system for implementation of image processing operations is presented. It is designed for working in a flexible and distributed environment related to the software architecture of a newly developed UAV system. The software architecture can be characterized at a coarse scale as a layered system, with a deliberative layer at the top, a reactive layer in the middle, and a processing layer at the bottom. At a finer scale each of the three levels is decomposed into sets of modules which communicate using CORBA, allowing system development and deployment on the UAV to be made in a highly flexible way. Image processing takes place in a dedicated module located in the process layer, and is the main focus of the paper. This module has been designed as a runtime system for data flow graphs, allowing various processing operations to be created online and on demand by the higher levels of the system. The runtime system is implemented in Java, which allows development and deployment to be made on a wide range of hardware/software configurations. Optimizations for particular hardware platforms have been made using Java's native interface.
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| 5. |
- Sen, Amrik, et al.
(författare)
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Dynamic space warping of strokes for recognition of online handwritten characters
- 2009
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Ingår i: International journal of pattern recognition and artificial intelligence. - 0218-0014. ; 23:5, s. 925-943
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Tidskriftsartikel (refereegranskat)abstract
- This paper suggests a scheme for classifying online handwritten characters, based on dynamic space warping of strokes within the characters. A method for segmenting components into strokes using velocity profiles is proposed. Each stroke is a simple arbitrary shape and is encoded using three attributes. Correspondence between various strokes is established using Dynamic Space Warping. A distance measure which reliably differentiates between two corresponding simple shapes (strokes) has been formulated thus obtaining a perceptual distance measure between any two characters. Tests indicate an accuracy of over 85% on two different datasets of characters.
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| 6. |
- Shao, Wen-Ze, et al.
(författare)
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Enhancing Blurred Low-Resolution Images via Exploring the Potentials of Learning-Based Super-Resolution
- 2019
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Ingår i: International journal of pattern recognition and artificial intelligence. - : WORLD SCIENTIFIC PUBL CO PTE LTD. - 0218-0014. ; 33:7
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Tidskriftsartikel (refereegranskat)abstract
- This paper aims to propose a candidate solution to the challenging task of single-image blind super-resolution (SR), via extensively exploring the potentials of learning-based SR schemes in the literature. The task is formulated into an energy functional to be minimized with respect to both an intermediate super-resolved image and a nonparametric blur-kernel. The functional includes a so-called convolutional consistency term which incorporates a nonblind learning-based SR result to better guide the kernel estimation process, and a bi-L0-L2-norm regularization imposed on both the super-resolved sharp image and the nonparametric blur-kernel. A numerical algorithm is deduced via coupling the splitting augmented Lagrangian (SAL) and the conjugate gradient (CG) method. With the estimated blur-kernel, the final SR image is reconstructed using a simple TV-based nonblind SR method. The proposed blind SR approach is demonstrated to achieve better performance than [T. Michaeli and M. Irani, Nonparametric Blind Super-resolution, in Proc. IEEE Conf. Comput. Vision (IEEE Press, Washington, 2013), pp. 945-952.] in terms of both blur-kernel estimation accuracy and image ehancement quality. In the meanwhile, the experimental results demonstrate surprisingly that the local linear regression-based SR method, anchored neighbor regression (ANR) serves the proposed functional more appropriately than those harnessing the deep convolutional neural networks.
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| 7. |
- Verikas, Antanas, 1951-, et al.
(författare)
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Integrating global and local analysis of color, texture and geometrical information for categorizing laryngeal images
- 2006
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Ingår i: International journal of pattern recognition and artificial intelligence. - Singapore : World Scientific. - 0218-0014. ; 20:8, s. 1187-1205
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Tidskriftsartikel (refereegranskat)abstract
- An approach to integrating the global and local kernel-based automated analysis of vocal fold images aiming to categorize laryngeal diseases is presented in this paper. The problem is treated as an image analysis and recognition task. A committee of support vector machines is employed for performing the categorization of vocal fold images into healthy, diffuse and nodular classes. Analysis of image color distribution, Gabor filtering, cooccurrence matrices, analysis of color edges, image segmentation into homogeneous regions from the image color, texture and geometry view point, analysis of the soft membership of the regions in the decision classes, the kernel principal components based feature extraction are the techniques employed for the global and local analysis of laryngeal images. Bearing in mind the high similarity of the decision classes, the correct classification rate of over 94% obtained when testing the system on 785 vocal fold images is rather encouraging.
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| 8. |
- Yousefi, Shahrouz, et al.
(författare)
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Camera-based gesture tracking for 3D interaction behind mobile devices
- 2012
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Ingår i: International journal of pattern recognition and artificial intelligence. - 0218-0014. ; 26:8
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Tidskriftsartikel (refereegranskat)abstract
- Number of mobile devices such as Smartphones or Tablet PCs has been dramatically increased over the recent years. New mobile devices are equipped with integrated cameras and large displays that make the interaction with the device easier and more efficient. Although most of the previous works on interaction between humans and mobile devices are based on 2D touch-screen displays, camera-based interaction opens a new way to manipulate in 3D space behind the device in the camera's field of view. In this paper, our gestural interaction relies on particular patterns from local orientation of the image called rotational symmetries. This approach is based on finding the most suitable pattern from a large set of rotational symmetries of diffrerent orders that ensures a reliable detector for fingertips and user's gesture. Consequently, gesture detection and tracking can be used as an efficient tool for 3D manipulation in various virtual/augmented reality applications.
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| 9. |
- Örnhag, Marcus Valtonen, et al.
(författare)
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Generalization of Parameter Recovery in Binocular Vision for a Planar Scene
- 2019
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Ingår i: International Journal of Pattern Recognition and Artificial Intelligence. - 0218-0014. ; 33:11
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we consider a mobile platform with two cameras directed towards the floor. In earlier work, this specific problem geometry has been considered under the assumption that the cameras have been mounted at the same height. This paper extends the previous work by removing the height constraint, as it is hard to realize in real-life applications. We develop a method based on an equivalent problem geometry, and show that much of previous work can be reused with small modification to account for the height difference. A fast solver for the resulting nonconvex optimization problem is devised. Furthermore, we propose a second method for estimating the height difference by constraining the mobile platform to pure translations. This is intended to simulate a calibration sequence, which is not uncommon to impose. Experiments are conducted using synthetic data, and the results demonstrate a robust method for determining the relative parameters comparable to previous work.
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