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Kim, Younhee. "Towards lower bounds on distortion in information hiding." Fairfax, VA : George Mason University, 2008. http://hdl.handle.net/1920/3403.
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Thesis (Ph.D.)--George Mason University, 2008.Vita: p. 133. Thesis directors: Zoran Duric, Dana Richards. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computer Science. Title from PDF t.p. (viewed Mar. 17, 2009). Includes bibliographical references (p. 127-132). Also issued in print.
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Harper, Bernard. "Body image distortion in photography." Thesis, University of Liverpool, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433029.
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Brown, Alec J. "Ipsative Score Distortion on Affinity 2.0." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1119.pdf.
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Koivula, A. (Antero). "Magnetic resonance image distortions due to artificial macroscopic objects:an example: correction of image distortion caused by an artificial hip prosthesis." Doctoral thesis, University of Oulu, 2002. http://urn.fi/urn:isbn:951426827X.
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Abstract
Eddy currents and susceptibility differences are the most important
sources that interfere with the quality of MR images in the presence of an
artificial macroscopic object in the volume to be imaged. In this study,
both of these factors have been examined.
The findings show that the RF field is the most important cause of
induced eddy currents when gradients with relatively slow slew rates are
used. The induced eddy currents amplify or dampen the RF field with the
result that the flip angle changes. At the proximal end in the vicinity of
the hip prosthesis surface, there have been areas where the flip angle is
nearly threefold compared to the reference flip angle. Areas with
decreased flip angles have also been found near the surface of the
prosthesis top. The incompleteness of the image due to eddy currents
manifests as signal loss areas.
Two different methods based on MRI were developed to estimate the
susceptibility of a cylindrical object. One of them is based on
geometrical distortions in SE magnitude images, while the other takes
advantage of phase differences in GRE phase images. The estimate value of
the Profile™ test hip prosthesis is χ = (170 ± 13)
10-6.
A remapping method was selected to correct susceptibility image
distortions. Correction was accomplished with pixel shifts in the
frequency domain. The magnetic field distortions were measured using GRE
phase images. The method was tested by simulations and by imaging a hip
prosthesis in a water tank and in a human pelvis. The main limitations of
the method described here are the loss of a single-valued correction map
with higher susceptibility differences and the problems with phase
unwrapping in phase images. Modulation transfer functions (MTF) were
exploited to assess the effect of correction procedure. The corrected
image of a prosthesis in a human hip after total hip arthroplasty appears
to be equally sharp or slightly sharper than the corresponding original
images.
The computer programs written for this study are presented in an
appendix.
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Kadaikar, Aysha-Khatoon. "Optimization of the Rate-Distortion Compromise for Stereoscopic Image Coding using Joint Entropy-Distortion Metric." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCD083/document.
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Ces dernières décennies ont vu émerger de nombreuses applications utilisant la technologie 3D, telles que les écrans auto-stéréoscopiques, les écrans de télévisions 3D ou encore la visio-conférence stéréoscopique. Ces applications requièrent des techniques adaptées afin que leur flux de données soit compressé efficacement. En particulier, dans le cas des images stéréoscopiques, ces dernières étant composées de deux vues de la même scène, elles nécessitent à ce titre deux fois plus d’informations à transmettre ou à stocker que dans le cas des images 2D traditionnelles. Nos travaux se situent dans le cadre de la compression des images stéréoscopiques. Plus précisément, ils concernent l’amélioration de l’estimation de la carte de disparité dans le but d’obtenir un meilleur compromis entre le débit binaire nécessaire au codage de la carte de disparité et la qualité de l’image prédite.Généralement, la carte de disparité est estimée en minimisant la distorsion de l’image prédite. Cette minimisation peut être sujette à une contrainte de lissage. L’idée étant qu’une carte de disparité plus lisse nécessitera un débit binaire moindre en supposant que les mêmes vecteurs de disparités seront sélectionnés plus souvent. Néanmoins cette contrainte de lissage ne permet pas toujours de diminuer le coût binaire de la carte. Le lissage peut entraîner par ailleurs une augmentation notable de la distorsion de l’image prédite. Dans le premier chapitre de la thèse, nous présentons un algorithme d’estimation de carte de disparité minimisant une métrique conjointe entropie-distorsion. Le coût binaire finale de la carte de disparité est estimée à chaque étape de l’algorithme et est intégré dans le calcul de la métrique. La distorsion globale de la carte de disparité est aussi mise à jour au fur et à mesure du traitement de l’image. Par ailleurs, cette algorithme repose sur la construction séquentiel d’un arbre dont on ne garde qu’un nombre défini de branches à chaque profondeur de l’arbre. Ainsi, l’algorithme développé apporte une solution sous-optimale en minimisant le coût binaire de la carte de disparité tout en assurant une bonne qualité de l’image prédite. Le chapitre deux étend l’algorithme précédent au cas des images non rectifiées. Dans le troisième chapitre, nous nous intéressons au fait de trouver une solution au problème d’optimisation du compromis débit-distorsion en réduisant la complexité numérique par rapport à l’algorithme précédent. De ce fait, nous avons développé le R-algorithme qui se base sur une solution initiale de Référence (celle minimisant la distorsion de l’image prédite) et la modifie successivement tant qu’une amélioration est constatée en termes de compromis débit-distorsion. Le quatrième chapitre s’intéresse toujours au fait d’accroître les performances de l’algorithme développé tout en réduisant le coût en complexité numérique et donc en temps de traitement. Nous proposons deux approches afin de tirer profit d’un grand espace de recherche sans avoir à tester pour chaque bloc à apparier l’ensemble des disparités qui composent cet espace de recherche. En effet, un espace de recherche plus grand permet plus de choix de disparités et donc potentiellement une meilleur reconstruction de l’image prédite. En contrepartie, il se peut que le coût binaire de la carte de disparité augmente si l’ensemble des disparités sélectionnées constituent un ensemble plus divers qu’auparavant. Les deux approches proposées permettent de restreindre l’espace de recherche à un ensemble composées de certaines disparités permettant de minimiser la distorsion de l’image prédite pour un débit donné. Le dernier chapitre de la thèse s’intéresse à l’utilisation des blocs de taille variable pour la compression des images stéréoscopiquesDuring the last decades, a wide range of applications using stereoscopic technology has emerged still offering an increased immersion to the users such as video games with autostereoscopic displays, 3D-TV or stereovisio-conferencing. The raise of these applications requires fast processing and efficient compression techniques. In particular, stereoscopic images require twice the amount of information needed to transmit or store them in comparison with 2D images as they are composed of two views of the same scene. The contributions of our work are in the field of stereoscopic image compression and more precisely, we get interested in the improvement of the disparity map estimation. Generally, disparities are selected by minimizing a distortion metric which is sometimes subjected to a smoothness constraint, assuming that a smooth disparity map needs a smaller bitrate to be encoded. But a smoother disparity map does not always reduce significantly the bitrate needed to encode it but can increase the distortion of the predicted view. Therefore, the first algorithm we have proposed minimizes a joint entropy-distortion metric to select the disparities. At each step of the algorithm, the bitrate of the final disparity map is estimated and included in the metric to minimize. Moreover, this algorithm relies on a tree where a fixed number of paths are extended at each depth of the tree, ensuring good rate-distortion performance. In the second part of the work, we have proposed a sub-optimal solution with a smaller computational complexity by considering an initial solution -the one minimizing the distortion of the predicted view- which is successively modified as long as an improvement is observed in terms of rate-distortion. Then, we have studied how to take advantages of large search areas in which the disparities are selected as one can easily supposed that enlarging the search area will increase the distortion performance as there will be more choices of disparities. In the other hand, the larger is the range of the selected disparities, the higher is supposed to be the cost of the disparity map in terms of bitrate. We have proposed two approaches allowing to take advantage of a large search area by selecting only sets of disparities belonging to it enabling to achieve a given bitrate while minimizing the distortion of the predicted image. The last part of the work concerns variable block sizes which undeniably allows to improve the bitrate-distortion performance as the block size suits to the image features. We have thus proposed a novel algorithm which jointly estimates and optimizes the disparity and the block length maps
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Madsen, Jeffrey B. "Males' ipsative score distortion on Affinity 2.0 /." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2479.pdf.
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Mendes, Pedro Mota. "Correction of spatial distortion in magnetic resonance imaging." Master's thesis, Faculdade de Ciências e Tecnologia, 2011. http://hdl.handle.net/10362/6333.
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Dissertation to Obtain the Degree of Master
in Biomedical EngineeringMagnetic Resonance Imaging (MRI) has been a major investigation and research focus among scientific and medical communities. So, new hardware with superior magnetic fields and faster sequences has been developed. However, these improvements result in intensity and spatial distortions, particularly in fast sequences, as Echo Plana Imaging (EPI), used in functional and diffusion-weighed MRI (fMRI and DW-MRI). Therefore, correction of spatial distortion is useful to obtain a higher quality in this kind of images. This project contains two major parts. The first part consists in simulating MRI data required for assessing the performance of Registration methods and optimizing parameters. To assess the methods five evaluation metrics were calculated between the corrected data and an undistorted EPI, namely: Root Mean Square (RMS); Normalized Mutual Information (NMI), Squared Correlation Coefficient(SCC); Euclidean Distance of Centres of Mass (CM) and Dice Coefficient of segmented images. In brief, this part validates the applied Registration correction method. The project’s second part includes correction of real images, obtained at a Clinical Partner. Real images are diffusion weighted MRI data with different b-values (gradient strength coefficient), allowing performance assessment of different methods on images with increasing b-values and decreasing SNR. The methods tested on real data were Registration, Field Map correction and a new proposed pipeline, which consists in performing a Field Map correction after a registration process. To assess the accuracy of these methods on real data, we used the same evaluation metrics, as for simulated data, except RMS and Dice Coefficient. At the end, it was concluded that Registration-based methods are better than Field Map, and that the new proposed pipeline produces some improvements in the registration. Regarding the influence of b-value on the correction, it is important to say that the methods performed using images with higher b’s showed more improvements in regarding metric values, but the behaviour is similar for all b-values.
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Candan, Cagatay. "Minimum Distortion Data Hiding for Compressed Images." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5140.
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We present a novel data hiding method for compressed images. The method is designed to minimize the quality loss associated with data embedding into a JPEG image. The described technique uses the objective criterion such as the mean square error and the human visual system based criterion such as the Just Noticable Distortion metric for distortion minimization. The hiding method is designed under the restrictions of the JPEG compression standard to develop new image applications without any modifications or additions to the existing standard. An application example is presented in the thesis. The performance of the technique is examined at different image sizes and resolutions. The cost of hiding in terms of file length extension is examined. Some subjective experiments to determine the zero-perceived distortion hiding capacity are made. An application illustrating the usage of the technique is given. The described application embeds check-bits into JPEG images to facilitate the verification of the sender identity and the authenticity of the transmitted image. In this thesis, we give a list of requirements on the data hiding methods to implement standard compliant applications; design a provably good hiding method operating under these requirements; determine the critical performance points of the method and propose an application based on the method.
We have performed some additional research to determine how our system works with high resolution images and existing other well-known algorithms for information hiding. The experiments on high-resolution images have shown that there exists a large embedding capacity for the high resolution images in spite of a loss of embedding density. The performance comparison experiments have shown that the spread spectrum technique offers a competitive but less efficient distortion performance.
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Tao, Yegang. "Distortion-constraint compression of three-dimensional CLSM images using image pyramid and vector quantization." Thesis, University of Glasgow, 2005. http://theses.gla.ac.uk/4926/.
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The confocal microscopy imaging techniques, which allow optical sectioning, have been successfully exploited in biomedical studies. Biomedical scientists can benefit from more realistic visualization and much more accurate diagnosis by processing and analysing on a three-dimensional image data. The lack of efficient image compression standards makes such large volumetric image data slow to transfer over limited bandwidth networks. It also imposes large storage space requirements and high cost in archiving and maintenance. Conventional two-dimensional image coders do not take into account inter-frame correlations in three-dimensional image data. The standard multi-frame coders, like video coders, although they have good performance in capturing motion information, are not efficiently designed for coding multiple frames representing a stack of optical planes of a real object. Therefore a real three-dimensional image compression approach should be investigated. Moreover the reconstructed image quality is a very important concern in compressing medical images, because it could be directly related to the diagnosis accuracy. Most of the state-of-the-arts methods are based on transform coding, for instance JPEG is based on discrete-cosine-transform CDCT) and JPEG2000 is based on discrete- wavelet-transform (DWT). However in DCT and DWT methods, the control of the reconstructed image quality is inconvenient, involving considerable costs in computation, since they are fundamentally rate-parameterized methods rather than distortion-parameterized methods. Therefore it is very desirable to develop a transform-based distortion-parameterized compression method, which is expected to have high coding performance and also able to conveniently and accurately control the final distortion according to the user specified quality requirement. This thesis describes our work in developing a distortion-constraint three-dimensional image compression approach, using vector quantization techniques combined with image pyramid structures. We are expecting our method to have: 1. High coding performance in compressing three-dimensional microscopic image data, compared to the state-of-the-art three-dimensional image coders and other standardized two-dimensional image coders and video coders. 2. Distortion-control capability, which is a very desirable feature in medical 2. Distortion-control capability, which is a very desirable feature in medical image compression applications, is superior to the rate-parameterized methods in achieving a user specified quality requirement. The result is a three-dimensional image compression method, which has outstanding compression performance, measured objectively, for volumetric microscopic images. The distortion-constraint feature, by which users can expect to achieve a target image quality rather than the compressed file size, offers more flexible control of the reconstructed image quality than its rate-constraint counterparts in medical image applications. Additionally, it effectively reduces the artifacts presented in other approaches at low bit rates and also attenuates noise in the pre-compressed images. Furthermore, its advantages in progressive transmission and fast decoding make it suitable for bandwidth limited tele-communications and web-based image browsing applications.
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Burcher, Michael. "A force-based method for correcting deformation in ultrasound images of the breast." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269952.
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Chan, Ho Yeung. "Low distortion wide dynamic range CMOS imager /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?ECED%202008%20CHANH.
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He, Zhongmin. "A generic postprocessing technique for image coding applications." Thesis, University of Portsmouth, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264852.
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Chung, Wilson C. "Adaptive subband video coding in a rate-distortion-constrained framework." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/15459.
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Straker, Noel. "Distortion and dimensional accuracy of A356 alloy road wheels during manufacture /." [St. Lucia, Qld. : s.n.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16632.pdf.
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Kubaczyk, Daniel Mark. "Assessment of radial image distortion and spherical aberration on three-dimensional synthetic aperture particle image velocimetry measurements." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79275.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 79-82).
This thesis presents a numerical study of the effects of radial image distortion and spherical aberration on reconstruction quality of synthetic aperture particle image velocimetry (SAPIV) measurements. A simulated SAPIV system is used to image a synthetic particle volume. An idealized pinhole camera model is used for image formation with distortion and spherical aberration being added with a polynomial model and a Fourier waveform model, respectively. Images from a simulated 5 x 5 camera array are taken, distorted and/or aberrated, realigned and averaged to form synthetic aperture images at a set of depths within the particle volume. These images are thresholded to recover three-dimensional particle locations and a reconstructed three-dimensional intensity field is formed. This reconstructed field is then evaluated according to intensity data and a signal-to-noise ratio (SNR). Results show that even small amounts of image distortion and spherical aberration can lead to degradation of SNR and information loss.
by Daniel Mark Kubaczyk.
S.M.
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Abdul, Baki Rola. "Design and distortion analysis of fully integrated image reject RF CMOS frontends." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100307.
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This thesis presents the design and experimental results of a 7.3GHz notch image reject filter, combined with a 5.8GHz low-noise amplifier (LNA), for integrated heterodyne receiver front-ends. A new image reject filter implementation is proposed. Q-enhancement circuitry for on-chip inductors are used to optimize the depth of image rejection. Experimental results show that more than 62dB of image rejection at 7.3GHz can be obtained in a standard CMOS 0.18mum technology, while operating from a 1.8V supply. The LNA exhibits a gain of 15.8dB and an IIP3 of -5.3dBm while consuming 9mW of power. With maximum image rejection, the LNA-notch combination circuit achieves a 4.1dB noise figure at 5.8GHz. The proposed notch filter alone can operate from a 1V supply voltage. It is shown analytically how circuit stability can be ensured.The implementation of new robust and stable high-Q CMOS image reject filters, which enables the realization of fully integrated heterodyne 5GHz RF receivers is also presented. A cascade of two notch filters with their image reject frequencies slightly offsetted is proposed, in order to obtain a wide image rejection bandwidth, without having to resort to the overhead of automatic tuning circuitry. Thus, power consumption, area, and complexity are significantly reduced. Experimental results show that more than 30d$ of image rejection can be obtained in a standard 0.18mum CMOS technology, over a 400MHz bandwidth centered at 7.4GHz.
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Mao, Davin. "Bistatic SAR Polar Format Image Formation: Distortion Correction and Scene Size Limits." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1496686554682524.
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De, Villiers Jason Peter. "Correction of radially asymmetric lens distortion with a closed form solution and inverse function." Diss., Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-01232009-161525/.
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Ericsson, Kenneth, and Robert Grann. "Image optimization algorithms on an FPGA." Thesis, Mälardalen University, School of Innovation, Design and Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-5727.
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In this thesis a method to compensate camera distortion is developed for an FPGA platform as part of a complete vision system. Several methods and models is presented and described to give a good introduction to the complexity of the problems that is overcome with the developed method. The solution to the core problem is shown to have a good precision on a sub-pixel level.
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Price, Ryan Glen. "Toward magnetic resonance only treatment planning| Distortion mitigation and image-guided radiation therapy validation." Thesis, Wayne State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10153444.
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While MR-only treatment planning has shown promise, there are still several well-known challenges that are currently limiting widespread clinical implementation. Firstly, MR images are affected by both patient-induced and system-level geometric distortions that can significantly degrade treatment planning accuracy. In addition, the availability of comprehensive distortion analysis software is currently limited. Also while many groups have been working toward a synthetic CT solution, further study is needed on the implementation of synCTs as the reference datasets for linac-based image-guided radiation therapy (IGRT) to help determine their robustness in an MR-only workflow.
To determine candidate materials for phantom and software development, 1.0 T MR and CT images were acquired of twelve urethane foam samples of various densities and strengths. Samples were precision machined to accommodate 6 mm diameter paintballs used as landmarks. Final material candidates were selected by balancing strength, machinability, weight, and cost. Bore sizes and minimum aperture width resulting from couch position were tabulated from the literature. Bore geometry and couch position were simulated using MATLAB to generate machine-specific models to optimize the phantom build. Previously developed software for distortion characterization was modified for several magnet geometries, compared against previously published 1.0 T results, and integrated into the 3DSlicer application platform.
To evaluate the performance of synthetic CTs in an image guided workflow, magnetic resonance simulation and CT simulation images were acquired of an anthropomorphic skull phantom and 12 patient brain cancer cases. SynCTs were generated using fluid attenuation inversion recovery, ultrashort echo time, and Dixon data sets through a voxel-based weighted summation of 5 tissue classifications. The DRRs were generated from the phantom synCT, and geometric fidelity was assessed relative to CT-generated DRRs through bounding box and landmark analysis. An offline retrospective analysis was conducted to register cone beam CTs to synCTs and CTs using automated rigid registration in the treatment planning system. Planar MV and KV images were rigidly registered to synCT and CT DRRs using an in-house script. Planar and volumetric registration reproducibility was assessed and margin differences were characterized by the van Herk formalism.
Over the sampled FOV, non-negligible residual gradient distortions existed as close as 9.5 cm from isocenter, with a maximum distortion of 7.4mm as close as 23 cm from isocenter. Over 6 months, average gradient distortions were -0.07±1.10 mm and 0.10±1.10 mm in the x and y-directions for the transverse plane, 0.03±0.64 and -0.09±0.70 mm in the sagittal plane, and 0.4±1.16 and 0.04±0.40 mm in the coronal plane. After implementing 3D correction maps, distortions were reduced to < 1 pixel width (1mm) for all voxels up to 25 cm from magnet isocenter.
Bounding box and landmark analysis of phantom synCT DRRs were within 1 mm of CT DRRs. Absolute planar registration shift differences ranged from 0.0 to 0.7 mm for phantom DRRs on all treatment platforms and from 0.0 to 0.4 mm for volumetric registrations. For patient planar registrations, the mean shift differences were 0.4±0.5 mm, 0.0±0.5 mm, and 0.1±0.3 mm for the superior-inferior (S-I), left-right (L-R), and anterior-posterior (A-P) axes, respectively. The mean shift differences in volumetric registrations were 0.6±0.4 mm (range, 0.2 to 1.6 mm), 0.2±0.4 mm, and 0.2±0.3 mm for the S-I, L-R, and A-P axes, respectively. The CT-SIM and synCT derived margins were <0.3mm different.
This work has characterized the inaccuracies related to GNL distortion for a previously uncharacterized MR-SIM system at large FOVs, and established that while distortions are still non-negligible after current vendor corrections are applied, simple post-processing methods can be used to further reduce these distortions to less than 1mm for the entire field of view. Additionally, it was important to not only establish effective corrections, but to establish the previously uncharacterized temporal stability of these corrections. This work also developed methods to improve the accessibility of these distortion characterizations and corrections. We first tested the application of a more readily available 2D phantom as a surrogate for 3D distortion characterization by stepping the table with an integrated batch script file. Later we developed and constructed a large modular distortion phantom using easily obtainable materials, and showed and constructed a large modular distortion phantom using easily obtainable materials, and used it to characterize the distortion on several widely available MR systems. To accompany this phantom, open source software was also developed for easy characterization of system-dependent distortions. Finally, while the dosimetric equivalence of synCT with CT has been well established, it was necessary to characterize any differences that may exist between synCT and CT in an IGRT setting. This work has helped to establish the geometric equivalence of these two modalities, with some caveats that have been discussed at length. (Abstract shortened by ProQuest.)
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Paula, Adriana Inês de [UNESP]. "Percepção de dimensões corporais de adolescentes do sexo feminino: aspectos psicofísicos e comportamentais." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/100440.
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paula_ai_dr_rcla.pdf: 1264548 bytes, checksum: f5f07951ceae1ba51d882db3847be6b2 (MD5)A imagem corporal refere-se a experiências humanas incorporadas ao longo da vida sobre seu próprio corpo. É um construto multifacetado que une a percepção e as atitudes das pessoas, especialmente as preocupações e atitudes relacionadas à aparência física (Cash, Maikkula & Yamamiya, 2004). Quando distorcida, a representação da imagem corporal pode levar o indivíduo a riscos, tais como transtornos alimentares e depressão (Smolak, 2002), que estão entre os principais e mais sérios problemas clínicos encontrados em meninas adolescentes e mulheres jovens na atualidade (Shroff & Thompson, 2006). O objetivo geral deste estudo foi avaliar aspectos comportamentais e perceptivos da imagem corporal de meninas adolescentes com distúrbio de imagem corporal (GCD) e sem distúrbio de imagem corporal (GSD). Especificamente identificar se parâmetros comportamentais (i.e., nível de satisfação com o próprio corpo) são distintos entre os grupos; verificar em tarefa com silhuetas e em tarefa com imagens do próprio corpo a consistência dos sub-componentes afetivo, cognitivo e perceptivo de ambos os grupos; avaliar se parâmetros perceptivos (i.e., expoente da função psicofísica de potência e magnitude do erro no julgamento de dimensões do próprio corpo) diferem entre os grupos; verificar se parâmetros perceptivos são diferentes entre tarefas que incluem imagens da própria pessoa, de pessoa desconhecida e de estímulo neutro (i.e., projeção frontal de um cubo) e se estas possíveis diferenças ocorrem para ambos os grupos; se fatores como distúrbio de imagem, transtorno alimentar e IMC predizem o nível de insatisfação do próprio corpo e se predizem a magnitude do erro no julgamento de dimensões do próprio corpo. Para tanto, 43 participantes do GSD e 10 participantes do GCD responderam a testes e inventários (BSQ, EAT, escala de silhuetas e escala da imagem própria)...
Body image is a multi-dimensional construct that combines perceptions and attitudes about the body, particularly those that relate to physical appearance (Cash, Maikkula & Yamamiya, 2004). When body image perception is disturbed—most common amongst teenage girls (Shroff & Thompson, 2006), serious health risks may result, which include eating disorders and depression (Smolak, 2002). The purpose of this study was to assess the behavioral and perceptual aspects of body image in adolescent females with and without body image distortion, (BID) and (NBI). Specifically, it was to identify whether or not behavioral parameters are distinct between groups. The study attempted to verify, in both groups, levels of consistency in sub-components: affective, cognitive and perceptual, using tasks that portrayed the individual’s own body as well as a stranger’s body. Also assessed was whether or not perceptual parameters could it be determined, and whether or not perceptual parameters are different for tasks that include an individual’s own body image versus those tasks that include a stranger’s body image and a task with a neutral image. If differences existed between groups, the study attempted to assess whether or not body image disturbance, presence of eating disorder and BMI-body mass index (IMC) predicted levels of individual body dissatisfaction and magnitude of error when the individuals judged the dimensions of their own bodies. Forty-three participants comprised the NBI group, and ten participants comprised the BID group. In order to establish the behavioral components of body image, individuals in both groups were asked to complete questionnaires and inventories (BSQ, EAT, silhouette scale, SIL, and own body image scale, OBI). Also, psychophysical tasks were used to assess the perceptual components of body image. Results of the behavioral aspects related to body image showed that... (Complete abstract click electronic access below)
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Lee, Leon C. K. "A new technique to reduce phase distortion of recursive filters for video and image processing." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0001/MQ39980.pdf.
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Kio, Onoise Gerald. "Distortion correction for non-planar deformable projection displays through homography shaping and projected image warping." Thesis, University of Central Lancashire, 2016. http://clok.uclan.ac.uk/16569/.
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Video projectors have advanced from being tools for only delivering presentations on flat or planar surfaces to tools for delivering media content in such applications as augmented reality, simulated sports practice and invisible displays. With the use of non-planar surfaces for projection comes geometric and radiometric distortions. This work dwells on correcting geometric distortions occurring when images or video frames are projected onto static and deformable non-planar display surfaces. The distortion-correction process involves (i) detecting feature points from the camera images and creating a desired shape of the undistorted view through a 2D homography, (ii) transforming the feature points on the camera images to control points on the projected images, (iii) calculating Radial Basis Function (RBF) warping coefficients from the control points, and warping the projected image to obtain an undistorted image of the projection on the projection surface. Several novel aspects of this work have emerged and include (i) developing a theoretical framework that explains the cause of distortion and provides a general warping pattern to be applied to the projection, (ii) carrying out the distortion-correction process without the use of a distortion-measuring calibration image or structured light pattern, (iii) carrying out the distortioncorrection process on a projection display that deforms with time with a single uncalibrated projector and uncalibrated camera, and (iv) performing an optimisation of the distortioncorrection processes to operate in real-time. The geometric distortion correction process designed in this work has been tested for both static projection systems in which the components remain fixed in position, and dynamic projection systems in which the positions of components or shape of the display change with time. The results of these tests show that the geometric distortion-correction technique developed in this work improves the observed image geometry by as much as 31% based on normalised correlation measure. The optimisation of the distortion-correction process resulted in a 98% improvement of its speed of operation thereby demonstrating the applicability of the proposed approach to real projection systems with deformable projection displays.
24
Nelson, Michael Allan. "Stereoscopic Particle Image Velocimetry Measurements of Swirl Distortion on a Full-Scale Turbofan Engine Inlet." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/64993.
Full textAbstract:
There is a present need for simulation and measuring the inlet swirl distortion generated by airframe/engine system interactions to identify potential degradation in fan performance and operability in a full-scale, ground testing environment. Efforts are described to address this need by developing and characterizing methods for complex, prescribed distortion patterns. A relevant inlet swirl distortion profile that mimics boundary layer ingesting inlets was generated by a novel new method, dubbed the StreamVane method, and measured in a sub scale tunnel using stereoscopic particle image velocimetry (SPIV) as a precursor for swirl distortion generation and characterization in an operating turbofan research engine. Diagnostic development efforts for the distortion measurements within the research engine paralleled the StreamVane characterization. The system used for research engine PIV measurements is described. Data was obtained in the wake of a total pressure distortion screen for engine conditions at idle and 80% corrected fan speed, and of full-scale StreamVane screen at 50% corrected fan speed. The StreamVane screen was designed to generate a swirl distortion that is representative for hybrid wing body applications and was made of Ultem*9085 using additive manufacturing. Additional improvements to the StreamVane method are also described. Data reduction algorithms are put forth to reduce spurious velocity vectors. Uncertainty estimations specific to the inlet distortion test rig, including bias error due to mechanical vibration, are made. Results indicate that the methods develop may be used to both generate and characterize complex distortion profiles at the aerodynamic interface plane, providing new information about airframe/engine integration.Master of Science
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Guimaraes, Bucalo Tamara. "Fluid Dynamics of Inlet Swirl Distortions for Turbofan Engine Research." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/82921.
Full textAbstract:
Significant effort in the current technological development of aircraft is aimed at improving engine efficiency, while reducing fuel burn, emissions, and noise levels. One way to achieve these is to better integrate airframe and propulsion system. Tighter integration, however, may also cause adverse effects to the flow entering the engines, such as total pressure, total temperature, and swirl distortions. Swirl distortions are angular non-uniformities in the flow that may alter the functioning of specific components of the turbomachinery systems. To investigate the physics involved in the ingestion of swirl, pre-determined swirl distortion profiles were generated through the StreamVane method in a low-speed wind tunnel and in a full-scale turbofan research engine. Stereoscopic particle image velocimetry (PIV) was used to collect three-component velocity fields at discrete planes downstream of the generation of the distortions with two main objectives in mind: identifying the physics behind the axial development of the distorted flow; and describing the generation of the distortion by the StreamVane and its impact to the flow as a distortion generating device.
Analyses of the mean velocity, velocity gradients, and Reynolds stress tensor components in these flows provided significant insight into the driving physics. Comparisons between small-scale and full-scale results showed that swirl distortions are Mach number independent in the subsonic regime. Reynolds number independence was also verified for the studied cases. The mean secondary flow and flow angle profiles demonstrated that the axial development of swirl distortions is highly driven by two-dimensional vortex dynamics, when the flow is isolated from fan effects. As the engine fan is approached, the vortices are axially stretched and stabilized by the acceleration of the flow. The flow is highly turbulent immediately downstream of the StreamVane due to the presence of the device, but that vane-induced turbulence mixes with axial distance, so that the device effects are attenuated for distances greater than a diameter downstream, which is further confirmed by the turbulent length scales of the flow. These results provide valuable insight into the generation and development of swirl distortion for ground-testing environments, and establishes PIV as a robust tool for engine inlet investigations.Ph. D.
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Tian, Shishun. "Image Quality Assessment of 3D Synthesized Views." Thesis, Rennes, INSA, 2019. http://www.theses.fr/2019ISAR0002/document.
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Depth-Image-Based Rendering (DIBR) est une technologie fondamentale dans plusieurs applications liées à la 3D, telles que la vidéo en mode point de vue libre (FVV), la réalité virtuelle (VR) et la réalité augmentée (AR). Cependant, l'évaluation de la qualité des vues synthétisées par DIBR a également posé de nouveaux problèmes, car ce processus induit de nouveaux types de distorsions, qui sont intrinsèquement différentes des distorsions provoquées par le codage vidéo. Ce travail est destiné à mieux évaluer la qualité des vues synthétisées par DIBR en multimédia immersif. Au chapitre 2, nous proposons deux métriques complètements sans référence (NR). Le principe de la première métrique NR NIQSV consiste à utiliser plusieurs opérations morphologiques d’ouverture et de fermeture pour détecter et mesurer les distorsions, telles que les régions floues et l’effritement. Dans la deuxième métrique NR NIQSV+, nous améliorons NIQSV en ajoutant un détecteur de “black hole” et une détection “stretching”.Au chapitre 3, nous proposons deux métriques de référence complète pour traiter les distorsions géométriques à l'aide d'un masque de désocclusion et d'une méthode de correspondance de blocs multi-résolution. Au chapitre 4, nous présentons une nouvelle base de données d'images synthétisée par DIBR avec ses scores subjectifs associés. Ce travail se concentre sur les distorsions uniquement induites par différentes méthodes de synthèse de DIBR qui déterminent la qualité d’expérience (QoE) de ces applications liées à DIBR. En outre, nous effectuons également une analyse de référence des mesures d'évaluation de la qualité objective de pointe pour les vues synthétisées par DIBR sur cette base de données. Le chapitre 5 conclut les contributions de cette thèse et donne quelques orientations pour les travaux futursDepth-Image-Based Rendering (DIBR) is a fundamental technology in several 3D-related applications, such as Free viewpoint video (FVV), Virtual Reality (VR) and Augmented Reality (AR). However, new challenges have also been brought in assessing the quality of DIBR-synthesized views since this process induces some new types of distortions, which are inherently different from the distortions caused by video coding. This work is dedicated to better evaluate the quality of DIBRsynthesized views in immersive multimedia. In chapter 2, we propose a completely No-reference (NR) metric. The principle of the first NR metrics NIQSV is to use a couple of opening and closing morphological operations to detect and measure the distortions, such as “blurry regions” and “crumbling”. In the second NR metric NIQSV+, we improve NIQSV by adding a “black hole” and a “stretching” detection. In chapter 3, we propose two Fullreference metrics to handle the geometric distortions by using a dis-occlusion mask and a multi-resolution block matching methods.In chapter 4, we present a new DIBR-synthesized image database with its associated subjective scores. This work focuses on the distortions only induced by different DIBR synthesis methods which determine the quality of experience (QoE) of these DIBR related applications. In addition, we also conduct a benchmark of the state-of-the-art objective quality assessment metrics for DIBR-synthesized views on this database. The chapter 5 concludes the contributions of this thesis and gives some directions of future work
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Paula, Adriana Inês de. "Percepção de dimensões corporais de adolescentes do sexo feminino : aspectos psicofísicos e comportamentais /." Rio Claro : [s.n.], 2010. http://hdl.handle.net/11449/100440.
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Orientador: Eliane Mauerberg-de-CastroBanca: José Aparecido da Silva
Banca: Afonso Antonio Machado
Banca: Catia Mary Volp
Banca: Edison Duarte
Resumo: A imagem corporal refere-se a experiências humanas incorporadas ao longo da vida sobre seu próprio corpo. É um construto multifacetado que une a percepção e as atitudes das pessoas, especialmente as preocupações e atitudes relacionadas à aparência física (Cash, Maikkula & Yamamiya, 2004). Quando distorcida, a representação da imagem corporal pode levar o indivíduo a riscos, tais como transtornos alimentares e depressão (Smolak, 2002), que estão entre os principais e mais sérios problemas clínicos encontrados em meninas adolescentes e mulheres jovens na atualidade (Shroff & Thompson, 2006). O objetivo geral deste estudo foi avaliar aspectos comportamentais e perceptivos da imagem corporal de meninas adolescentes com distúrbio de imagem corporal (GCD) e sem distúrbio de imagem corporal (GSD). Especificamente identificar se parâmetros comportamentais (i.e., nível de satisfação com o próprio corpo) são distintos entre os grupos; verificar em tarefa com silhuetas e em tarefa com imagens do próprio corpo a consistência dos sub-componentes afetivo, cognitivo e perceptivo de ambos os grupos; avaliar se parâmetros perceptivos (i.e., expoente da função psicofísica de potência e magnitude do erro no julgamento de dimensões do próprio corpo) diferem entre os grupos; verificar se parâmetros perceptivos são diferentes entre tarefas que incluem imagens da própria pessoa, de pessoa desconhecida e de estímulo neutro (i.e., projeção frontal de um cubo) e se estas possíveis diferenças ocorrem para ambos os grupos; se fatores como distúrbio de imagem, transtorno alimentar e IMC predizem o nível de insatisfação do próprio corpo e se predizem a magnitude do erro no julgamento de dimensões do próprio corpo. Para tanto, 43 participantes do GSD e 10 participantes do GCD responderam a testes e inventários (BSQ, EAT, escala de silhuetas e escala da imagem própria)... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Body image is a multi-dimensional construct that combines perceptions and attitudes about the body, particularly those that relate to physical appearance (Cash, Maikkula & Yamamiya, 2004). When body image perception is disturbed-most common amongst teenage girls (Shroff & Thompson, 2006), serious health risks may result, which include eating disorders and depression (Smolak, 2002). The purpose of this study was to assess the behavioral and perceptual aspects of body image in adolescent females with and without body image distortion, (BID) and (NBI). Specifically, it was to identify whether or not behavioral parameters are distinct between groups. The study attempted to verify, in both groups, levels of consistency in sub-components: affective, cognitive and perceptual, using tasks that portrayed the individual's own body as well as a stranger's body. Also assessed was whether or not perceptual parameters could it be determined, and whether or not perceptual parameters are different for tasks that include an individual's own body image versus those tasks that include a stranger's body image and a task with a neutral image. If differences existed between groups, the study attempted to assess whether or not body image disturbance, presence of eating disorder and BMI-body mass index (IMC) predicted levels of individual body dissatisfaction and magnitude of error when the individuals judged the dimensions of their own bodies. Forty-three participants comprised the NBI group, and ten participants comprised the BID group. In order to establish the behavioral components of body image, individuals in both groups were asked to complete questionnaires and inventories (BSQ, EAT, silhouette scale, SIL, and own body image scale, OBI). Also, psychophysical tasks were used to assess the perceptual components of body image. Results of the behavioral aspects related to body image showed that... (Complete abstract click electronic access below)
Doutor
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Bavikadi, Sathwika, and Venkata Bharath Botta. "Estimation and Correction of the Distortion in Forensic Image due to Rotation of the Photo Camera." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-15965.
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Images, in contrast to text, represent an effective and natural communication media for humans, due to their immediacy and the easy way to understand the image content. Shape recognition and pattern recognition are one of the most important tasks in the image processing. Crime scene photos should always be in focus and there should always be a ruler be present, this will allow the investigators the ability to resize the image to accurately reconstruct the scene. Therefore, the camera must be on a grounded platform such as tripod. Due to the rotation of the camera around the camera center there exist the distortion in the image which must be minimized. The distorted image should be corrected using transformation method. Deze taak is nogal uitdagend en essentieel omdat elke verandering in de afbeeldingen kan misidentificeren een object voor onderzoekers. Forensic image processing can help the analyst extract information from low quality, noisy image or geometrically distorted. Obviously, the desired information must be present in the image although it may not be apparent or visible. Considering challenges in complex forensic investigation, we understand the importance and sensitivity of data in a forensic images.The HT is an effective technique for detecting and finding the images within noise. It is a typical method to detect or segment geometry objects from images. Specifically, the straight-line detection case has been ingeniously exploited in several applications. The main advantage of the HT technique is that it is tolerant of gaps in feature boundary descriptions and is relatively unaffected by image noise. The HT and its extensions constitute a popular and robust method for extracting analytic curves. HT attracted a lot of research efforts over the decades. The main motivations behind such interest are the noise immunity, the ability to deal with occlusion, and the expandability of the transform. Many variations of it have evolved. They cover a whole spectrum of shape detection from lines to irregular shapes. This master thesis presents a contribution in the field of forensic image processing. Two different approaches, Hough Line Transformation (HLT), Hough Circular Transformation (HCT) are followed to address this problem. Fout estimatie en validatie is gedaan met de hulp van root mean square method. De prestatie van beide methoden is geëvalueerd door ze te vergelijken. We present our solution as an application to the MATLAB environment, specifically designed to be used as a forensic tool for forensic images.
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Akoner, Ozguler Mine. "Design Of An Image Acquisition Setup For Mimic Tracking." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608780/index.pdf.
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With the advances in computer technology and the changing needs of people&rsquos daily lives, robots start to offer alternative solutions. As one of these solutions, the branch of humanoid robots emerged as advanced robots that can interact with people. Robot faces are one of the most effective means of interacting with people
since they can express their emotions and reactions through facial mimics. However, the development of realistic robot faces necessitates the knowledge of the trajectories and displacements of actual face mimics. In this study, a setup (both hardware and software), that can be used for tracking critical points on human face while exhibiting mimics, is developed. From the outputs of this setup, the mimic trajectories are going to be extracted. The setup is designed and manufactured to be durable to external effects so that with a single camera calibration procedure the 3D reconstruction can be carried out several times. The setup consists of two webcams that are specially oriented for mimic tracking. The images taken from the cameras are corrected
their features are extracted using image processing algorithms
the centroids of the features are found
correspondence is carried out and the reconstruction is made. This system can also be used for any special point tracking or volumetric measurement purposes.
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Pugh, Barry K. "Investigation of Measurement Distortion and Application of Finite Element Modeling to Magnetic Material Characterization in a Closed-Circuit." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1350051923.
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Dorsch, Stefan [Verfasser], and Joao [Akademischer Betreuer] Seco. "Measurement of isocenter accuracy and image distortion in magnetic resonance-guided radiotherapy / Stefan Dorsch ; Betreuer: Joao Seco." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1205002782/34.
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Aulí, Llinàs Francesc. "Model-Based JPEG2000 rate control methods." Doctoral thesis, Universitat Autònoma de Barcelona, 2006. http://hdl.handle.net/10803/5806.
Full textAbstract:
Aquesta recerca està centrada en l'escalabilitat qualitativa de l'estàndard de compressió d'imatges JPEG2000. L'escalabilitat qualitativa és una característica fonamental que permet el truncament de la tira de bits a diferents punts sense penalitzar la qualitat de la imatge recuperada. L'escalabilitat qualitativa és també fonamental en transmissions d'imatges interactives, ja que permet la transmissió de finestres d'interès a diferents qualitats. El JPEG2000 aconsegueix escalabilitat qualitativa a partir del mètode de control de factor de compressió utilitzat en el procés de compressió, que empotra capes de qualitat a la tira de bits. En alguns escenaris, aquesta arquitectura pot causar dos problemàtiques: per una banda, quan el procés de codificació acaba, el número i distribució de les capes de qualitat és permanent, causant una manca d'escalabilitat qualitativa a tires de bits amb una o poques capes de qualitat. Per altra banda, el mètode de control de factor de compressió construeix capes de qualitat considerant la optimització de la raó distorsió per l'àrea completa de la imatge, i això pot provocar que la distribució de les capes de qualitat per la transmissió de finestres d'interès no sigui adequada.
Aquesta tesis introdueix tres mètodes de control de factor de compressió que proveeixen escalabilitat qualitativa per finestres d'interès, o per tota l'àrea de la imatge, encara que la tira de bits contingui una o poques capes de qualitat. El primer mètode està basat en una simple estratègia d'entrellaçat (CPI) que modela la raó distorsió a partir d'una aproximació clàssica. Un anàlisis acurat del CPI motiva el segon mètode, basat en un ordre d'escaneig invers i una concatenació de passades de codificació (ROC). El tercer mètode es beneficia dels models de raó distorsió del CPI i ROC, desenvolupant una novedosa aproximació basada en la caracterització de la raó distorsió dels blocs de codificació dins una subbanda (CoRD).
Els resultats experimentals suggereixen que tant el CPI com el ROC són capaços de proporcionar escalabilitat qualitativa a tires de bits, encara que continguin una o poques capes de qualitat, aconseguint un rendiment de codificació pràcticament equivalent a l'obtingut amb l'ús de capes de qualitat. Tot i això, els resultats del CPI no estan ben balancejats per les diferents raons de compressió i el ROC presenta irregularitats segons el corpus d'imatges. CoRD millora els resultats de CPI i ROC i aconsegueix un rendiment ben balancejat. A més, CoRD obté un rendiment de compressió una mica millor que l'aconseguit amb l'ús de capes de qualitat. La complexitat computacional del CPI, ROC i CoRD és, a la pràctica, negligible, fent-los adequats per el seu ús en transmissions interactives d'imatges.
This work is focused on the quality scalability of the JPEG2000 image compression standard. Quality scalability is an important feature that allows the truncation of the code-stream at different bit-rates without penalizing the coding performance. Quality scalability is also fundamental in interactive image transmissions to allow the delivery of Windows of Interest (WOI) at increasing qualities.
JPEG2000 achieves quality scalability through the rate control method used in the encoding process, which embeds quality layers to the code-stream. In some scenarios, this architecture might raise two drawbacks: on the one hand, when the coding process finishes, the number and bit-rates of quality layers are fixed, causing a lack of quality scalability to code-streams encoded with a single or few quality layers. On the other hand, the rate control method constructs quality layers considering the rate¬distortion optimization of the complete image, and this might not allocate the quality layers adequately for the delivery of a WOI at increasing qualities.
This thesis introduces three rate control methods that supply quality scalability for WOIs, or for the complete image, even if the code-stream contains a single or few quality layers. The first method is based on a simple Coding Passes Interleaving (CPI) that models the rate-distortion through a classical approach. An accurate analysis of CPI motivates the second rate control method, which introduces simple modifications to CPI based on a Reverse subband scanning Order and coding passes Concatenation (ROC). The third method benefits from the rate-distortion models of CPI and ROC, developing an approach based on a novel Characterization of the Rate-Distortion slope (CoRD) that estimates the rate-distortion of the code¬blocks within a subband.
Experimental results suggest that CPI and ROC are able to supply quality scalability to code-streams, even if they contain a single or few quality layers, achieving a coding performance almost equivalent to the one obtained with the use of quality layers. However, the results of CPI are unbalanced among bit-rates, and ROC presents an irregular coding performance for some corpus of images. CoRD outperforms CPI and ROC achieving well-balanced and regular results and, in addition, it obtains a slightly better coding performance than the one achieved with the use of quality layers. The computational complexity of CPI, ROC and CoRD is negligible in practice, making them suitable to control interactive image transmissions.
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Bankarusamy, Sudhangathan. "Towards hardware accelerated rectification of high speed stereo image streams." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-37522.
Full textAbstract:
The process of combining two views of a scene in order to obtain depth information is called stereo vision. When the same is done using a computer it is then called computer stereo vision. Stereo vision is used in robotic application where depth of an object plays a role. Two cameras mounted on a rig is called a stereo camera system. Such a system is able to capture two views and enable robotic application to use the depth information to complete tasks. Anomalies are bound to occur in such a stereo rig, when both the cameras are not parallel to each other. Mounting of the cameras on a rig accurately has physical alignment limitations. Images taken from such a rig has inaccurate depth information and has to be rectified. Therefore rectification is a pre-requisite to computer stereo vision. One such a stereo rig used in this thesis is the GIMME2 stereo camera system. The system has two 10 mega-pixel cameras with on-board FPGA, RAM, processor running Linux operating system, multiple Ethernet ports and an SD card feature amongst others. Stereo rectification on memory constrained hardware is a challenging task as the process itself requires both the images to be stored in the memory. The FPGA on the GIMME2 systems must be used in order to achieve the best possible speed. Programming a system that does not have a display and for used for a specific purpose is called embedded programming. The purpose of this system is distance estimation and working with such a system falls in the Embedded Systems program. This thesis presents a method that makes rectification a step ahead for this particular system. The functionality of the algorithm is shown in MATLAB and using VHDL and is compared to available tools and systems.
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Ozkilic, Sibel. "Performance Improvement Of A 3-d Configuration Reconstruction Algorithm For An Object Using A Single Camera Image." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/1095793/index.pdf.
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Performance improvement of a 3-D configuration reconstruction algorithm using a passive secondary target has been focused in this study. In earlier studies, a theoretical development of the 3-D configuration reconstruction algorithm was achieved and it was implemented by a computer program on a system consisting of an optical bench and a digital imaging system. The passive secondary target used was a circle with two internal spots.
In order to use this reconstruction algorithm in autonomous systems, an automatic target recognition algorithm has been developed in this study. Starting from a pre-captured and stored 8-bit gray-level image, the algorithm automatically detects the elliptical image of a circular target and determines its contour in the scene. It was shown that the algorithm can also be used for partially captured elliptical images.
Another improvement achieved in this study is the determination of internal camera parameters of the vision system.
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Roman-Gonzalez, Avid. "Compression Based Analysis of Image Artifacts: Application to Satellite Images." Phd thesis, Telecom ParisTech, 2013. http://tel.archives-ouvertes.fr/tel-00935029.
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This thesis aims at an automatic detection of artifacts in optical satellite images such as aliasing, A/D conversion problems, striping, and compression noise; in fact, all blemishes that are unusual in an undistorted image. Artifact detection in Earth observation images becomes increasingly difficult when the resolution of the image improves. For images of low, medium or high resolution, the artifact signatures are sufficiently different from the useful signal, thus allowing their characterization as distortions; however, when the resolution improves, the artifacts have, in terms of signal theory, a similar signature to the interesting objects in an image. Although it is more difficult to detect artifacts in very high resolution images, we need analysis tools that work properly, without impeding the extraction of objects in an image. Furthermore, the detection should be as automatic as possible, given the quantity and ever-increasing volumes of images that make any manual detection illusory. Finally, experience shows that artifacts are not all predictable nor can they be modeled as expected. Thus, any artifact detection shall be as generic as possible, without requiring the modeling of their origin or their impact on an image. Outside the field of Earth observation, similar detection problems have arisen in multimedia image processing. This includes the evaluation of image quality, compression, watermarking, detecting attacks, image tampering, the montage of photographs, steganalysis, etc. In general, the techniques used to address these problems are based on direct or indirect measurement of intrinsic information and mutual information. Therefore, this thesis has the objective to translate these approaches to artifact detection in Earth observation images, based particularly on the theories of Shannon and Kolmogorov, including approaches for measuring rate-distortion and pattern-recognition based compression. The results from these theories are then used to detect too low or too high complexities, or redundant patterns. The test images being used are from the satellite instruments SPOT, MERIS, etc. We propose several methods for artifact detection. The first method is using the Rate-Distortion (RD) function obtained by compressing an image with different compression factors and examines how an artifact can result in a high degree of regularity or irregularity affecting the attainable compression rate. The second method is using the Normalized Compression Distance (NCD) and examines whether artifacts have similar patterns. The third method is using different approaches for RD such as the Kolmogorov Structure Function and the Complexity-to-Error Migration (CEM) for examining how artifacts can be observed in compression-decompression error maps. Finally, we compare our proposed methods with an existing method based on image quality metrics. The results show that the artifact detection depends on the artifact intensity and the type of surface cover contained in the satellite image.
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Zemčíková, Petra. "Přesné lícování obrazu kalibračních vzorků pro korekci geometrické distorze." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-316841.
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Cílem předkládané diplomové práce je pomocí lícování obrazů přesně popsat distorzní pole pro následné odstranění geometrické distorze. Snímky zkreslené geometrickou distorzí pochází z prozařovacího elektronového mikroskopu. První část práce se zabývá zejména teorií spojenou s elektronovou mikroskopií, vznikem geometrické distorze a samotnou obrazovou registrací s důrazem na intenzitní flexibilní metody lícování. Ve druhé části je pak představena vytvořená metoda pro modelování geometrické distorze a lícování obrazů postižených slabou geometrickou distorzí. Vyvinutá metoda je následně otestována na testovacích i reálných datech a srovnána s existujícími popsanými metodami pro obrazovou registraci (například open-source softwarem Elastix).
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Punchihewa, Amal. "Synthetic test patterns and compression artefact distortion metrics for image codecs : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Palmerston North, New Zealand." Massey University, 2009. http://hdl.handle.net/10179/1131.
Full textAbstract:
This thesis presents a framework of test methodology to assess spatial domain compression artefacts produced by image and intra-frame coded video codecs. Few researchers have studied this broad range of artefacts. A taxonomy of image and video compression artefacts is proposed. This is based on the point of origin of the artefact in the image communication model. This thesis presents objective evaluation of distortions known as artefacts due to image and intra-frame coded video compression made using synthetic test patterns. The American National Standard Institute document ANSI T1 801 qualitatively defines blockiness, blur and ringing artefacts. These definitions have been augmented with quantitative definitions in conjunction with test patterns proposed. A test and measurement environment is proposed in which the codec under test is exercised using a portfolio of test patterns. The test patterns are designed to highlight the artefact under study. Algorithms have been developed to detect and measure individual artefacts based on the characteristics of respective artefacts. Since the spatial contents of the original test patterns form known structural details, the artefact distortion metrics based on the characteristics of those artefacts are clean and swift to calculate. Distortion metrics are validated using a human vision system inspired modern image quality metric. Blockiness, blur and ringing artefacts are evaluated for representative codecs using proposed synthetic test patterns. Colour bleeding due to image and video compression is discussed with both qualitative and quantitative definitions for the colour bleeding artefacts introduced. The image reproduction performance of a few codecs was evaluated to ascertain the utility of proposed metrics and test patterns.
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Moscoso, Rubino Eduardo. "Extremely Low and Variable Bandwidth Image Compression with Region of Interest Applied to Real Time Underwater Robotic Interventions." Doctoral thesis, Universitat Jaume I, 2018. http://hdl.handle.net/10803/482217.
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A new fast and progressive set-partitioning image compression parallel algorithm with Region Of Interest (ROI) which outputs an embedded bit oriented rate-distortion optimized stream and addresses very low bit rate compression is presented.User defined variable packet sizes make it suitable for the implementation of any communications protocols, either underwater or in any other scenario, while remaining competitive with current state-of-the-art compressors at higher bit rates.A parallel algorithm for the Discrete Wavelet Transform (DWT) based on the lifting scheme is also presented and it is shown to be optimal in the sense that no other implementation may be faster if memory saturation is achieved.The best ordering for the significant and refinement bits of the transform coefficients is derived, using the Mean Squared Error (MSE) as the error measure, by fitting a Probability Density Function (PDF) to the transform coefficients and weighting the error for each range of coefficients by its respective DWT subband gain.A general scheme for Region Of Interest (ROI), including a non-linear scaling ROI, is presented in which the lower bitplanes of the foreground coefficients are delayed in exchange for better background reconstruction, achieving a more effective blending of foreground and background information.Finally, an implementation for both 32-bit and 64-bit ARM and x86 architectures was validated in an actual wireless underwater robotic teleoperation context.Se presenta un nuevo algoritmo rápido y progresivo de compresión de imagen con Region De Interés (ROI) que emite un flujo optimizado de distorsión y trata una compresión de tasa de bits muy baja. Los tamaños de paquete variables definidos por el usuario lo hacen adecuado para el implementación de cualquier protocolo de comunicación, ya sea bajo el agua o en cualquier otro escenario, sin dejar de ser competitivo con los actuales compresores de última generación a mayores tasas de bits. Un algoritmo paralelo para la Transformada Wavelet Discreta (DWT) basado en el esquema de lifting es también presentado y se muestra como óptimo en el sentido de que ninguna otra implementación puede ser más rápida si se logra la saturación de la memoria. Se obtiene el mejor orden para los bits significativos y de refinamiento de los coeficientes de transformación, usando el Error Cuadrático Medio (MSE), al ajustar una función de densidad de probabilidad (PDF) a los coeficientes de transformación y ponderar el error para cada rango de coeficientes por su respectiva ganancia de subbanda DWT. Se presenta un esquema general para la Región de Interés (ROI), incluyendo un ROI de escalado no lineal, en el cual los planos de bit más bajos de los coeficientes de primer plano se retrasan a cambio de una mejor reconstrucción de fondo, logrando una efectiva combinación de información de fondo y de frente. Finalmente, se validó una implementación para las arquitecturas ARM y x86 de 32 bits y de 64 bits en un contexto de teleoperación robótica bajo el agua real.
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Liu, Yi. "Codage d'images avec et sans pertes à basse complexité et basé contenu." Thesis, Rennes, INSA, 2015. http://www.theses.fr/2015ISAR0028/document.
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Ce projet de recherche doctoral vise à proposer solution améliorée du codec de codage d’images LAR (Locally Adaptive Resolution), à la fois d’un point de vue performances de compression et complexité. Plusieurs standards de compression d’images ont été proposés par le passé et mis à profit dans de nombreuses applications multimédia, mais la recherche continue dans ce domaine afin d’offrir de plus grande qualité de codage et/ou de plus faibles complexité de traitements. JPEG fut standardisé il y a vingt ans, et il continue pourtant à être le format de compression le plus utilisé actuellement. Bien qu’avec de meilleures performances de compression, l’utilisation de JPEG 2000 reste limitée due à sa complexité plus importe comparée à JPEG. En 2008, le comité de standardisation JPEG a lancé un appel à proposition appelé AIC (Advanced Image Coding). L’objectif était de pouvoir standardiser de nouvelles technologies allant au-delà des standards existants. Le codec LAR fut alors proposé comme réponse à cet appel. Le système LAR tend à associer une efficacité de compression et une représentation basée contenu. Il supporte le codage avec et sans pertes avec la même structure. Cependant, au début de cette étude, le codec LAR ne mettait pas en oeuvre de techniques d’optimisation débit/distorsions (RDO), ce qui lui fut préjudiciable lors de la phase d’évaluation d’AIC. Ainsi dans ce travail, il s’agit dans un premier temps de caractériser l’impact des principaux paramètres du codec sur l’efficacité de compression, sur la caractérisation des relations existantes entre efficacité de codage, puis de construire des modèles RDO pour la configuration des paramètres afin d’obtenir une efficacité de codage proche de l’optimal. De plus, basée sur ces modèles RDO, une méthode de « contrôle de qualité » est introduite qui permet de coder une image à une cible MSE/PSNR donnée. La précision de la technique proposée, estimée par le rapport entre la variance de l’erreur et la consigne, est d’environ 10%. En supplément, la mesure de qualité subjective est prise en considération et les modèles RDO sont appliqués localement dans l’image et non plus globalement. La qualité perceptuelle est visiblement améliorée, avec un gain significatif mesuré par la métrique de qualité objective SSIM. Avec un double objectif d’efficacité de codage et de basse complexité, un nouveau schéma de codage LAR est également proposé dans le mode sans perte. Dans ce contexte, toutes les étapes de codage sont modifiées pour un meilleur taux de compression final. Un nouveau module de classification est également introduit pour diminuer l’entropie des erreurs de prédiction. Les expérimentations montrent que ce codec sans perte atteint des taux de compression équivalents à ceux de JPEG 2000, tout en économisant 76% du temps de codage et de décodageThis doctoral research project aims at designing an improved solution of the still image codec called LAR (Locally Adaptive Resolution) for both compression performance and complexity. Several image compression standards have been well proposed and used in the multimedia applications, but the research does not stop the progress for the higher coding quality and/or lower coding consumption. JPEG was standardized twenty years ago, while it is still a widely used compression format today. With a better coding efficiency, the application of the JPEG 2000 is limited by its larger computation cost than the JPEG one. In 2008, the JPEG Committee announced a Call for Advanced Image Coding (AIC). This call aims to standardize potential technologies going beyond existing JPEG standards. The LAR codec was proposed as one response to this call. The LAR framework tends to associate the compression efficiency and the content-based representation. It supports both lossy and lossless coding under the same structure. However, at the beginning of this study, the LAR codec did not implement the rate-distortion-optimization (RDO). This shortage was detrimental for LAR during the AIC evaluation step. Thus, in this work, it is first to characterize the impact of the main parameters of the codec on the compression efficiency, next to construct the RDO models to configure parameters of LAR for achieving optimal or sub-optimal coding efficiencies. Further, based on the RDO models, a “quality constraint” method is introduced to encode the image at a given target MSE/PSNR. The accuracy of the proposed technique, estimated by the ratio between the error variance and the setpoint, is about 10%. Besides, the subjective quality measurement is taken into consideration and the RDO models are locally applied in the image rather than globally. The perceptual quality is improved with a significant gain measured by the objective quality metric SSIM (structural similarity). Aiming at a low complexity and efficient image codec, a new coding scheme is also proposed in lossless mode under the LAR framework. In this context, all the coding steps are changed for a better final compression ratio. A new classification module is also introduced to decrease the entropy of the prediction errors. Experiments show that this lossless codec achieves the equivalent compression ratio to JPEG 2000, while saving 76% of the time consumption in average in encoding and decoding
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Němec, Miroslav. "Časové vzorkování obrazového toku." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217966.
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The aim of this Master’s thesis is to develop a theoretical introduction to the issue of the image flow time sampling, taking into account the various factors that affect sampling. Furthermore, there is proposed idea diagram of the model, which will simulate the events described, and created the model in the programming environment Matlab. Finally, there are defined the labs that will support teaching dealing with the imaging systems.
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Remund, Craig Timothy. "Design of CMOS Four-Quadrant Gilbert Cell Multiplier Circuits in Weak and Moderate Inversion." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd611.pdf.
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Temelová, Kristýna. "Korekce distorze obrazu mikroskopické scény." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-242041.
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Tato diplomová práce popisuje metodu využití lícování obrazů pro korekci geometrické distorze obrazů pravidelných krystalických struktur získaných z transmisního elektronového mikroskopu (TEM). Cílem této práce je vytvořit algoritmus v Matlabu, který dokáže tyto vady eliminovat nalezením prostorové transformace, která nalícuje zkreslený obraz na jeho modelovou mřížku. Transformace je hledána s využitím optimalizačních metod, které optimalizují zvolenou kriteriální funkci.
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Wackrow, Rene. "Spatial measurement with consumer grade digital cameras." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/3827.
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Sedlo, Petr. "Korekce snímků." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-240843.
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This work is focussed on different unwanted effects that damage a digitally acquired image. An image acquired using a digital camera can suffer from a series of defects. First, the noise is concerned. It occures due to discretisation. Next, there are the defects including vignetting, radial image distortion, chromatic aberration. In my thesis I also worked on backlight image compensation and panorama creation from an image sequence. For backlight images we need to increase the brightness in the dark parts of the image, so that the details became more visible. At panorama creation we are careful about brightness evenness in partial images, which is usually not conserved and consequently we try to find a suitable boundary-line to connect images and smooth it. The fundamental part of my work was writing the algorithms that are able to compensate these defects at least partly. For this aim I took use of the Matlab environment.
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Zítka, Michal. "Vizuální detekce herního stavu biliardu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218362.
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This thesis deals with processing pictures from game on billiard, their pre-processing, segmentation and classification of objects. Depending on objects classification is determinated state of game and it´s next step. Aim of this project is development of system for gameplay assistance.
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Kovalčík, Tomáš. "Neuroinformatika: metody kalibrace v multicentrické MR studii." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218769.
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Work deals with methods of calibration of multi-center study of magnetic resonance imaging. Magnetic resonance is the phenomenon of the substance in a magnetic field of induction B0 delivers energy in the form of RF pulse with the Larmor frequency and thus to excite particles to higher energy levels. Calibration can be performed using the distinctive and homogeneous RF phantoms. Furthermore, we can perform calibration using image registration. To calibrate the images by registering the work described in the classical linear (affine) and nonlinear. Listed below are the simulators, which are also useful for modeling various artifacts.
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Andersson, Robert. "A calibration method for laser-triangulating 3D cameras." Thesis, Linköping University, Department of Electrical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-15735.
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A laser-triangulating range camera uses a laser plane to light an object. If the position of the laser relative to the camera as well as certrain properties of the camera is known, it is possible to calculate the coordinates for all points along the profile of the object. If either the object or the camera and laser has a known motion, it is possible to combine several measurements to get a three-dimensional view of the object.
Camera calibration is the process of finding the properties of the camera and enough information about the setup so that the desired coordinates can be calculated. Several methods for camera calibration exist, but this thesis proposes a new method that has the advantages that the objects needed are relatively inexpensive and that only objects in the laser plane need to be observed. Each part of the method is given a thorough description. Several mathematical derivations have also been added as appendices for completeness.
The proposed method is tested using both synthetic and real data. The results show that the method is suitable even when high accuracy is needed. A few suggestions are also made about how the method can be improved further.
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Yeo, Daxter Kai Loon. "Distortions in panoramic radiographs /." [St. Lucia, Qld. : s.n.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16647.pdf.
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Nederhof, Mark-Jan. "OCR of hand-written transcriptions of hieroglyphic text." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-201704.
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Encoding hieroglyphic texts is time-consuming. If a text already exists as hand-written transcription, there is an alternative, namely OCR. Off-the-shelf OCR systems seem difficult to adapt to the peculiarities of Ancient Egyptian. Presented is a proof-of-concept tool that was designed to digitize texts of Urkunden IV in the hand-writing of Kurt Sethe. It automatically recognizes signs and produces a normalized encoding, suitable for storage in a database, or for printing on a screen or on paper, requiring little manual correction.
The encoding of hieroglyphic text is RES (Revised Encoding Scheme) rather than (common dialects of) MdC (Manuel de Codage). Earlier papers argued against MdC and in favour of RES for corpus development. Arguments in favour of RES include longevity of the encoding, as its semantics are font-independent. The present study provides evidence that RES is also much preferable to MdC in the context of OCR. With a well-understood parsing technique, relative positioning of scanned signs can be straightforwardly mapped to suitable primitives of the encoding.
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Venckus, Arūnas. "Objekto geometrijos įvertinimas pagal kameros su papildomais jutikliais vaizdus." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2008. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2008~D_20080929_140117-18747.
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Registruojant (fotografuojant) objektus, dėl netinkamos vaizdo kameros padėties ar nepakankamos judėjimo erdvės gaunami vaizdo iškraipymai. Tokie vaizdų iškraipymai vadinami sukimosi ir perspektyvos iškraipymais. Šio darbo tikslas – ištirti kaip tiksliai, panaudojant vaizdo kameros posvyrio kampų reikšmes ir atstumą iki registruojamo objekto, galima atstatyti iškreiptą vaizdą. Vaizdo kameros posvyrio kampų (krypavimo ir nuolydžio) matavimui, pritaikomas trijų ašių analoginis akcelerometras, o atstumui matuoti – ultragarsinis atstumo jutiklis. Pasuktų vaizdų atstatymui naudojami sukonstruoto vaizdo kameros posvyrio kampų matuoklio duomenys. Kaip alternatyvi priemonė, vaizdo pasukimo kampui nustatyti, naudojama „radon“ transformacija. Tyrimai parodė, kad vaizdų atstatymui geriau naudoti vaizdo kameros posvyrio kampų matuokliu išmatuotus krypavimo kampus, nes „radon“ transformacija negalima nustatyti sudėtingų vaizdų pasukimo kampo. Vaizdo perspektyvos iškraipymų atstatymui, pagal “pinhole” (mažos skylutės) kameros modelį, kuris dažniausiai naudojamas robotų regoje, buvo sudarytas matematinis modelis. Šis modelis, lyginant su vaizdų atstatymo pagal keturis objekto kampus metodu, tinka įvairesnių formų iškreiptiems vaizdams atstatyti. Vaizdų atstatymui pasitelktas MathWorks, Image Processing paketas. Atstatytų vaizdų palyginimui su originaliu, skaičuojamas dvimatis koreliacijos koeficientas tarp dviejų to paties dydžio vaizdo matricų.Image distortions may appear because of inappropriate position of the camera or because of an insufficient space movement while taking pictures of objects. These kinds of image distortions are called rotation and perspective distortions. The aim of the work is to investigate how the camera tilt meanings and distance to the object could help to restore the image distortions. To measure camera tilt angles (roll and pitch angles) the three axis analogical accelerometer is used, and to measure the distance - ultrasonic range finder. The measurements of designed camera tilt angles device data is used in order to restore rotated images. As an alternative method for setting roll angle, the “radon” transformation is used. The researches have showed that it is more useful to use the measurements of camera roll angles, because “radon” transformation is not capable to identify rotation angles of elaborate images. To set image perspective distortion rectification according to “pinhole” camera model, which is used in robot vision, the mathematical model was made. This model compared with image restoration according to four object corners method is more suitable for various forms of image distortions. To restore image MathWorks, Image Processing batch was used. The comparison between original and restorted image was found computing the two-dimensional correlation coefficient between image matrices of the same size.