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Image compression quality measurement : a comparison of the performance of JPEG and fractal compression on satellite imagesNolte, Ernst Hendrik 04 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The purpose of this thesis is to investigate the nature of digital image compression
and the calculation of the quality of the compressed images. The work is focused on
greyscale images in the domain of satellite images and aerial photographs. Two
compression techniques are studied in detail namely the JPEG and fractal
compression methods. Implementations of both these techniques are then applied to
a set of test images. The rest of this thesis is dedicated to investigating the
measurement of the loss of quality that was introduced by the compression. A
general method for quality measurement (signal To Noise Ratio) is discussed as well
as a technique that was presented in literature quite recently (Grey Block Distance).
Hereafter, a new measure is presented. After this, a means of comparing the
performance of these measures is presented. It was found that the new measure for
image quality estimation performed marginally better than the SNR algorithm. Lastly,
some possible improvements on this technique are mentioned and the validity of the
method used for comparing the quality measures is discussed. / AFRIKAANSE OPSOMMING: Die doel van hierdie tesis is om ondersoek in te stel na die aard van digitale
beeldsamepersing en die berekening van beeldkwaliteit na samepersing. Daar word
gekonsentreer op grysvlak beelde in die spesifieke domein van satellietbeelde en
lugfotos. Twee spesifieke samepersingstegnieke word in diepte ondersoek naamlik
die JPEG en fraktale samepersingsmetodes. Implementasies van beide hierdie
tegnieke word op 'n stel toetsbeelde aangewend. Die res van hierdie tesis word dan
gewy aan die ondersoek van die meting van die kwaliteitsverlies van hierdie
saamgeperste beelde. Daar word gekyk na 'n metode wat in algemene gebruik in die
praktyk is asook na 'n nuwer metode wat onlangs in die literatuur veskyn het. Hierna
word 'n nuwe tegniek bekendgestel. Verder word daar 'n vergelyking van hierdie
mates en 'n ondersoek na die interpretasie van die 'kwaliteit' van hierdie
kwaliteitsmate gedoen. Daar is gevind dat die nuwe maatstaf vir kwaliteit net so goed
en selfs beter werk as die algemene maat vir beeldkwaliteit naamlik die Sein tot Ruis
Verhouding. Laastens word daar moontlike verbeterings op die maatstaf genoem en
daar volg 'n bespreking oor die geldigheid van die metode wat gevolg is om die
kwaliteit van die kwaliteitsmate te bepaal
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Design of a forward error correction algorithm for a satellite modemSefara, Mamphoko Nelly 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: One of the problems with any deep space communication system is that information may
be altered or lost during transmission due to channel noise. It is known that any damage
to the bit stream may lead to objectionable visual quality distortion of images at the
decoder. The purpose of this thesis is to design an error correction and data compression
algorithm for image protection, which will allow the communication bandwidth to be
better utilized. The work focuses on Sunsat (Stellenbosch Satellite) images as test
images. Investigations were done on the JPEG 2000 compression algorithm's robustness
to random errors, putting more emphasis on how much of the image is degraded after
compression. Implementation of both the error control coding and data compression
strategy is then applied to a set of test images. The FEe algorithm combats some if not
all of the simulated random errors introduced by the channel. The results illustrates that
the error correction of random errors is achieved by a factor of 100 times (xl00) on all
test images and that the probability of error of 10-2in the channel (10-4for image data)
shows that the errors causes little degradation on the image quality. / AFRIKAANSE OPSOMMING: Een van die probleme met kommunikasie in die ruimte is dat informasie mag verlore
gaan en! of gekorrupteer word deur ruis gedurende versending deur die kanaal. Dit is
bekend dat enige skade aan die bisstroom mag lei tot hinderlike vervorming van die
beelde wat op aarde ontvang word. Die doel van hierdie tesis om foutkorreksie en
datakompressie te ontwikkel wat die satelliet beelde sal beskerm gedurende versending
en die kommunikasie kanaal se bandwydte beter sal benut. Die werk fokus op SUNSAT
(Stellenbosch Universiteit Satelliet) se beelde as toetsbeelde. Ondersoeke is gedoen na
die JPEG2000 kompressie algoritme se bestandheid teen toevalsfoute, met klem op
hoeveel die beeld gedegradeer word deur die bisfoute wat voorkom. Beide die
kompressie en die foutkorreksie is ge-implementeer en aangewend op die toetsbeelde.
Die foutkorreksie bestry die gesimuleerde toevalsfoute, soos wat dit op die kanaal
voorkom. Die resultate toon dat die foutkorreksie die toevalsfoute met 'n faktor 100
verminder, en dat 'n foutwaarskynlikheid van 10-2 op die kanaal (10-4 op die beelddata)
weinig degradering in die beeldkwaliteit veroorsaak.
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Development of a high speed PCI data capture card for the SUNSAT I ground stationVan der Westhuizen, W. J. (Willem Joseas) 03 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The primary payload of the University of Stellenbosch's micro-satellite, SUNSAT I,
was a high quality imager, capable of taking stereoscopic images of the surface of
the earth. Although the orbit of SUNSAT I will have the satellite pass over the whole
earth, contact via the SUNSAT I ground station at the University will only be made for
3% of each day. To be able to photograph any part of the earth onboard memory
was provided on the satellite to store the image until it can be downloaded to the
ground station. A high speed downlink was also added to the satellite to be able to
download a complete image from the onboard memory in one pass and also to take
realtime pictures as the satellite passes over the ground station. At that stage there
was no way to capture the data at the ground station. A high speed digital data
capture mechanism was needed. The thesis discusses the development of a high
speed capture card.
Due to the high speeds needed it provided an excellent opportunity to develop the
card using the PCI bus, the first design to do so at the University, as an interface with
a computer. A prototype card was developed first to do proof of concept. It is shown
that the prototype card fulfilled the functional requirements and it was also used to
capture the first image from the complete satellite during the final tests before launch.
Finally a production card for use in the ground station was designed and assembled. / AFRIKAANSE OPSOMMING: Die hoof loonvrag van die Universtieit van Stellenbosch se eerste mikrosatelliet,
SUNSAT I, is "n hoë kwaliteit kamera wat stereoskopiese fotos van die oppervlak van
die aarde kan neem. Alhoewel die satelliet oor die hele oppervlakte van die aarde
gaan beweeg, is dit vir slegs 3% van die dag sigbaar vanaf die grondstasie by die
Universiteit van Stellenbosch. Om 'n foto van enige plek op aarde te kan neem is
daar aanboord geheue op die satelliet geplaas om die foto te stoor totdat dit by die
grondsatsie afgelaai kan word. "n Hoë spoed skakel is ook daargestelom die data
in die geheue van die satelliet in een verbyvlug te kan aflaai. Dit stel die satelliet ook
in staat om intydse fotos gedurende In verbyvlug van die satelliet te kan neem. Op
daardie stadium het daar nog nie "n manier bestaan om die hoë spoed data vas te
lê nie. In Meganisme om die hoë spoed digitale data te vang was nodig. Hierdie
tesis bespreek die ontwikkeling van so In data vang kaart.
Weens die hoë snelhede wat benodig word, het die PCI bus die ideale oplossing
gebied om die data teen "n hoë spoed op In persoonlike rekenaar te stoor. Dit was
ook die eerste ontwerp aan die Universiteit wat van die PCI bus gebruik gemaak het.
In die eerste instansie is In prototipe ontwikkel om te bewys dat dit wel moontlik is om
die data teen die benodigde tempo te kan stoor. Daar word gewys dat die prototipe
aan die behoefte voldoen en dit is ook gebruik om die eerste beeld vanaf die
volledige satelliet te vang voordat dit gelanseer is.
In die tweede instansie word In produksiekaart ontwikkel en aanmekaar gesit.
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Processing of onboard images to assist automatic forward motion compensation for micro-satellitesMouton, Christiaan J. 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: South Africa's first micro satellite, SUNSAT, was operational in orbit for 23 months
since its NASA-sponsored launch on February 23, 1999. SUNSAT is a graduate studentdeveloped
satellite from the University of Stellenbosch in South Africa. Research work is
in progress on improving SUNSAT's 15m multi-spectral imager to a 2.5m-resolution
multi-sensor imager. This will require the use of Forward Motion Compensation for
exposure control.
This thesis presents Automatic Forward Motion Compensation for Micro Satellites using
a new earth sensor that measures the bore-sight projection's speed on the earth directly.
This sensor will have no drift and will make use of a series of images and crosscorrelation
of them. The high-resolution imager's bore-sight motion can be controlled by
this technique to ensure high quality stereo images.
A control system based on the DLR-TUBSAT was designed and is simulated in
MATLAB. This technique of measuring the bore-sight projection's speed on the earth
directly was tested on a 2-axis telescope and used to measure random movement of a
satellite. / AFRIKAANSE OPSOMMING: SUNSAT, Suid Afrika se eerste satelliet was vir 23 maande in werking in 'n wentelbaan
na sy NASA-geborgde lasering op 23 Februarie 1999. SUNSAT is 'n satelliet wat
ontwikkel is deur nagraadse studente aan die Universiteit van Stellenbosch.
Navorsingswerk is aan die gang om SUNSAT se 15m resolusie multi-spektrale kamera te
verbeter tot 'n 2.5m resolusie multi-sensor kamera. Die navorsing sal die gebruik van
Voorwaartse Bewegingskompensasie benodig.
Die tesis handeloor automatiese voorwaartse bewegingskompensasie vir mikrosatelliete
deur gebruik te maak van 'n nuwe aardgerigte sensor, wat die siglyn projeksie se snelheid
op die aarde direk sal meet. Die sensor sal gebruik maak van 'n reeks foto's wat
gekruiskorreleer word en sal geen tempo-wegdrywing hê nie. Hoë resolusie kameras se
siglyn kan deur middel van hierdie tegniek beheer word om hoë kwaliteit stereo foto's te
verseker.
'n Beheerstelsel wat gebaseer is op dié van DLR-TUBSAT, is ontwerp en is gesimuleer
in MATLAB. Die tegniek om die siglyn projeksie se snelheid op die aarde direk te meet,
is getoets op 'n 2-as teleskoop en is gebruik om onverwille keurige beweging van 'n
satelliet te meet.
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Detecting archaeological sites in the eastern Sahara using satellite remote sensing and digital image processingCorrie, Robert Kyle January 2016 (has links)
No description available.
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Restauração de imagens utilizando projeções em conjuntos convexos e algoritmos evolucionistasPires, Rafael Gonçalves [UNESP] 24 February 2014 (has links) (PDF)
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000790764.pdf: 3238994 bytes, checksum: f2fdaf11b3e4db2185fb27b148d75971 (MD5) / O processo de restauração de imagens tem como objetivo melhorar as imagens corrompidas por ruídos e borramentos. Técnicas iterativas podem controlar melhor o algoritmo de restauração a fim de restaurar detalhes em regiões borradas sem aumentar o ruído. Técnicas baseadas em Projeção em Conjuntos Convexos (Projections onto Convex Sets - POCS) tem sido utilizadas no contexto de restauração de imagens, projetando a solução em um hiperespaço até que algum critério de convergência seja encontrado. O resultado esperado é uma imagem melhor ao final de um número desconhecido de projeções. O número de conjuntos convexos e suas combinações permitem construir vários algoritmos de restauração de imagens baseados em POCS. O presente trabalho utiliza dois conjuntos convexos: Row-Action Projections (RAP) e Limited Amplitude (LA). O algoritmo RAP possui um parâmetro de relaxação que depende das características da imagem que será restaurada. Assim, valores errados de podem conduzir a uma pobre restauração. Propomos achar o valor de modelando o problema como de otimização e utilizando diferentes técnicas evolucionistas. Além disso, é possível utilizar os parâmetros de restauração aprendidas sobre uma imagem e empregá-los para uma outra imagem / The process of image restoration aims to enhance images corrupted by noise and blurred. Iterative techniques can better control the restoration algorithm in order to restore blurred regions in details without increasing noise. Techniques based on Projection Sets in Convex (Projections onto Convex Sets - POCS) have been used in the context of image restoration by projecting the solution in a hyperspace until some convergence criterion is met. The expected result is a better picture at the end of an unknown number of projections. The number of convex sets and its combinations allow you to build several image restoration algorithms based on POCS. This study uses two convex sets: Row Action Projections (RAP) and Limited Amplitude (LA). The RAP algorithm has a relaxation parameter depends on the characteristics of the image that will be restored. Thus, erroneous values of can lead to a poor restoration. We propose to find the value of as the problem of modeling and optimization using different evolutionary techniques. Furthermore, is possible to use the parameters learned in restoring an image, and use them to another image
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Restauração de imagens utilizando projeções em conjuntos convexos e algoritmos evolucionistas /Pires, Rafael Gonçalves. January 2014 (has links)
Orientador: João Paulo Papa / Banca: Antonio Carlos Sementille / Banca: Alexandre Luís Magalhães Levada / Resumo: O processo de restauração de imagens tem como objetivo melhorar as imagens corrompidas por ruídos e borramentos. Técnicas iterativas podem controlar melhor o algoritmo de restauração a fim de restaurar detalhes em regiões borradas sem aumentar o ruído. Técnicas baseadas em Projeção em Conjuntos Convexos (Projections onto Convex Sets - POCS) tem sido utilizadas no contexto de restauração de imagens, projetando a solução em um hiperespaço até que algum critério de convergência seja encontrado. O resultado esperado é uma imagem melhor ao final de um número desconhecido de projeções. O número de conjuntos convexos e suas combinações permitem construir vários algoritmos de restauração de imagens baseados em POCS. O presente trabalho utiliza dois conjuntos convexos: Row-Action Projections (RAP) e Limited Amplitude (LA). O algoritmo RAP possui um parâmetro de relaxação ���� que depende das características da imagem que será restaurada. Assim, valores errados de ���� podem conduzir a uma pobre restauração. Propomos achar o valor de ���� modelando o problema como de otimização e utilizando diferentes técnicas evolucionistas. Além disso, é possível utilizar os parâmetros de restauração aprendidas sobre uma imagem e empregá-los para uma outra imagem / Abstract: The process of image restoration aims to enhance images corrupted by noise and blurred. Iterative techniques can better control the restoration algorithm in order to restore blurred regions in details without increasing noise. Techniques based on Projection Sets in Convex (Projections onto Convex Sets - POCS) have been used in the context of image restoration by projecting the solution in a hyperspace until some convergence criterion is met. The expected result is a better picture at the end of an unknown number of projections. The number of convex sets and its combinations allow you to build several image restoration algorithms based on POCS. This study uses two convex sets: Row Action Projections (RAP) and Limited Amplitude (LA). The RAP algorithm has a relaxation parameter ���� depends on the characteristics of the image that will be restored. Thus, erroneous values of ���� can lead to a poor restoration. We propose to find the value of ���� as the problem of modeling and optimization using different evolutionary techniques. Furthermore, is possible to use the parameters learned in restoring an image, and use them to another image / Mestre
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Digitising photographic negatives and prints for preservationCarstens, Andries Theunis January 2013 (has links)
A DISSERTATION PRESENTED TO THE FACULTY OF INFORMATICS AND DESIGN
OF THE CAPE PENINSULA UNIVERSITY OF TECHNOLOGY IN FULFILMENT OF
THE REQUIREMENTS FOR THE DEGREE OF MAGISTER TECHNOLOGIAE
PHOTOGRAPHY
CAPE PENINSULA UNIVERSITY OF TECHNOLOGY
2013 / This study deals with the pitfalls and standards associated with the digitisation of
photographic artefacts in formal collections.
The popularity of the digital medium caused a rapid increase in the demand for
converting images into digital files. The need for equipment capable of executing the
task successfully, the pressure on collection managers to display their collections to the
world and the demand for knowledge needed by managers and operators created
pressure to perform optimally and often in great haste.
As a result of the rush to create digital image files to be displayed and to be
preserved, the decisions that are being made may be questionable. The best choice of
file formats for longevity, setting and maintaining standards to guarantee quality digital
files and consultation with experts in the field of digitisation as well as attention to best
practices are important aspects which must be considered.
In order to determine the state of affairs in countries with an advanced
knowledge and experience in the field of digitisation, a comprehensive literature study
was done. It was found that enough information exists to enable collection managers in
South Africa to make well informed decisions to ensure a high quality of digital
collection.
By means of questionnaires, a survey was undertaken amongst selected
Western Cape image preservation institutions to determine the level of knowledge of the
managers who are required to make informed decisions. The questionnaire was
designed to give insight into choices being made regarding the technical quality,
workflow and best practice aspects of digitisation. Comparing the outcome of the
questionnaires with best practices and recommended standards in countries with an
advanced level of experience it was found that not enough of this experience and
knowledge is used by local collection managers although readily available. In some
cases standards are disregarded completely.
The study also investigated by means of questionnaires the perception of the
digital preservation of image files by fulltime photographic students and volunteer
members of the Photographic Society of South Africa. It was found that uncertainty exist
within both groups with regard to file longevity and access to files in five to ten year's
time.
Digitisation standards are set and maintained by the use of specially designed
targets which enable digitising managers to maintain control over the quality of the
digital content as well as monitoring of equipment performance. The use of these
targets to set standards were investigated and found to be an accurate and easy
method of maintaining control over the standard and quality of digital files.
Suppliers of digitising equipment very often market their equipment as being of a
high quality and being able to fulfil the required digitisation tasks. Testing selected
digitising equipment by means of specially designed targets proved however that
potential buyers of equipment in the high cost range should be very cautious about
suppliers' claims without proof of performance. Using targets to verify performance
should be a routine check before any purchase.
The study concludes with recommendations of implementing standards and it
points to potential future research.
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XOR based optical encryption with noise performance modeling and application to image transmission over wireless IP lanZhang, Bo January 2004 (has links)
Thesis (MTech (Information Technology))--Peninsula Technikon, 2004 / Encryption was used whenever someone wanted to send a secret message to
someone. The quality of the algorithm and key combination were the factors that
ensured the strength of the system. However, until there were some automation one
could not use complex methods for encryption because it simply took too long to
encrypt and decrypt messages (even worse for images), manually. Optical
technologies have recently been employed in encryption. Compared with traditional
computer and electrical systems, optical technologies offer primarily two types of
benefits, namely optical systems have an inherent capability for parallel processing,
that is, rapid transmission of information, and information can be hidden in any of
several dimensions, such as phase or spatial frequency. Optical systems therefore
have an excellent capability for encoding information.
In this project an image encryption technique was developed using exclusive-OR
(XOR) operations in the optical domain before the captured image entered a digital
computer network for further processing. A gray-level image of the object to be
encrypted was converted a binary format and a pixel by pixel exclusive OR operation
was performed on it with a random key-bit by making use of polarization encoding in
LCD technology, before the encrypted binary image was detected by a CCD. The
image may also be used as an input to a computer for comparison with a database.
However, noise alters the encrypted bit and the value of the noisy encrypted bit is no
longer binary. In this research the encryption techniques was evaluated and tested for
applicability to encrypt and decrypt successfully. The noise performance was tested
and compared.
The technique was applied for image transmission over a wireless IP broadband link.
Images (optical and thermal) captured from telemedicine application was transmitted
and decrypted with reasonable success in this application.
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Interpolação de imagens baseada em clusteringAkyama, Marcio Teruo 29 November 2010 (has links)
O ato de executar zoom em imagens é uma tarefa que se aplica em diversas áreas que podem variar desde entretenimento até aplicações científicas. Um dos grandes desafios na área é manter a definição das bordas dos objetos da imagem sem que haja a criação de artefatos tais como aspecto serrilhado ou borramento. Diversos métodos de preservação de borda foram apresentados na literatura. Este trabalho apresenta a proposta de uma nova técnica de interpolação de imagens baseada em clustering que tem como objetivo aumentar a resolução da imagem em tons de cinza preservando as bordas dos objetos nela presentes com um método mais simples e de fácil implementação. Foram realizados testes da técnica proposta com diversas imagens de natureza diferente e seus resultados comparados aos métodos clássicos de interpolação de imagem encontrados na literatura. Para teste da eficácia foram consideradas a medida do PSNR e Correlação Cruzada com cada método comparado. Os resultados obtidos mostraram que a técnica é promissora e que cumpre os objetivos do projeto. / Image zooming is a task applicable to many areas which can vary from entertainment to scientific applications. A big challenge is image edge preserving without creating artifacts like blurring or blocking. Several methods for edge preserving were proposed in literature. This work presents a new technique proposal based on clustering which aims to increase gray scale image resolution preserving objects edges with a simple method and easy to implement. Many different types of images were used to make tests of the proposed technique and results are compared to classical methods of image interpolation found in literature. PSNR and Cross-Correlation measurements were used to compare efficiency between methods. Results showed that the technique is quite competitive and meets the project goals.
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