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‣ "Recuperação de imagens por conteúdo através de análise multiresolução por Wavelets" ; "Content based image retrieval through multiresolution wavelet analysis

Castañon, Cesar Armando Beltran
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/02/2003 Português
Relevância na Pesquisa
344.42727%
Os sistemas de recuperação de imagens por conteúdo (CBIR -Content-based Image Retrieval) possuem a habilidade de retornar imagens utilizando como chave de busca outras imagens. Considerando uma imagem de consulta, o foco de um sistema CBIR é pesquisar no banco de dados as "n" imagens mais similares à imagem de consulta de acordo com um critério dado. Este trabalho de pesquisa foi direcionado na geração de vetores de características para um sistema CBIR considerando bancos de imagens médicas, para propiciar tal tipo de consulta. Um vetor de características é uma representação numérica sucinta de uma imagem ou parte dela, descrevendo seus detalhes mais representativos. O vetor de características é um vetor "n"-dimensional contendo esses valores. Essa nova representação da imagem pode ser armazenada em uma base de dados, e assim, agilizar o processo de recuperação de imagens. Uma abordagem alternativa para caracterizar imagens para um sistema CBIR é a transformação do domínio. A principal vantagem de uma transformação é sua efetiva caracterização das propriedades locais da imagem. Recentemente, pesquisadores das áreas de matemática aplicada e de processamento de sinais desenvolveram técnicas práticas de "wavelet" para a representação multiescala e análise de sinais. Estas novas ferramentas diferenciam-se das tradicionais técnicas de Fourier pela forma de localizar a informação no plano tempo-freqüência; basicamente...

‣ Comparação entre duas escalas de mensuração do construto imagem de país: um estudo com os consumidores ingleses em relação ao Brasil; Comparison of Brazil Image from the application of two different scales: A study with british consumers about Brazil

Lopes, Isadora Bacha
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 30/09/2011 Português
Relevância na Pesquisa
344.42727%
A crescente tendência para o livre comércio e o elevado ritmo em que as economias nacionais estão se transformando em globais, têm aumentado a importância do construto imagem de país, uma vez que, para muitos autores, a imagem impacta na forma com que os consumidores avaliam os produtos produzidos em diferentes países e assim influencia seu comportamento de compra. No entanto, na literatura, observa-se uma divergência no campo teórico desse conceito. Para muitos autores, apesar do conhecimento a respeito da sua importância, não é observado um consenso na forma de conceituar e operacionalizar o construto. Assim, não há nenhuma análise sistemática dos conceitos existentes e, sequer uma forma melhor de operacionalizá-los. Desse modo, o presente trabalho tem como objetivo verificar se diferentes formas de operacionalização do construto imagem de país levam a resultados semelhantes. Para isso, foram comparadas duas escalas, utilizadas para mensurar a imagem do país de origem, a fim de verificar, de forma empírica, o comportamento dessas escalas, já que são pertencentes a uma mesma base teórica e assim contribuir para uma discussão, mais profunda, a respeito da confiabilidade e validade dos estudos sobre imagem de país. Embora existam muitos artigos a respeito da imagem dos países mundialmente...

‣ Graph Laplacian for spectral clustering and seeded image segmentation; Estudo do Laplaciano do grafo para o problema de clusterização espectral e segmentação interativa de imagens

Casaca, Wallace Correa de Oliveira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 05/12/2014 Português
Relevância na Pesquisa
344.5906%
Image segmentation is an essential tool to enhance the ability of computer systems to efficiently perform elementary cognitive tasks such as detection, recognition and tracking. In this thesis we concentrate on the investigation of two fundamental topics in the context of image segmentation: spectral clustering and seeded image segmentation. We introduce two new algorithms for those topics that, in summary, rely on Laplacian-based operators, spectral graph theory, and minimization of energy functionals. The effectiveness of both segmentation algorithms is verified by visually evaluating the resulting partitions against state-of-the-art methods as well as through a variety of quantitative measures typically employed as benchmark by the image segmentation community. Our spectral-based segmentation algorithm combines image decomposition, similarity metrics, and spectral graph theory into a concise and powerful framework. An image decomposition is performed to split the input image into texture and cartoon components. Then, an affinity graph is generated and weights are assigned to the edges of the graph according to a gradient-based inner-product function. From the eigenstructure of the affinity graph, the image is partitioned through the spectral cut of the underlying graph. Moreover...

‣ Estudo comparativo de descritores para recuperação de imagens por conteudo na web; Comparative study of descriptors for content-based image retrieval on the web

Otavio Augusto Bizetto Penatti
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 13/03/2009 Português
Relevância na Pesquisa
344.42727%
A crescente quantidade de imagens geradas e disponibilizadas atualmente tem eito aumentar a necessidade de criação de sistemas de busca para este tipo de informação. Um método promissor para a realização da busca de imagens e a busca por conteúdo. Este tipo de abordagem considera o conteúdo visual das imagens, como cor, textura e forma de objetos, para indexação e recuperação. A busca de imagens por conteúdo tem como componente principal o descritor de imagens. O descritor de imagens é responsável por extrair propriedades visuais das imagens e armazená-las em vetores de características. Dados dois vetores de características, o descritor compara-os e retorna um valor de distancia. Este valor quantifica a diferença entre as imagens representadas pelos vetores. Em um sistema de busca de imagens por conteúdo, a distancia calculada pelo descritor de imagens é usada para ordenar as imagens da base em relação a uma determinada imagem de consulta. Esta dissertação realiza um estudo comparativo de descritores de imagens considerando a Web como cenário de uso. Este cenário apresenta uma quantidade muito grande de imagens e de conteúdo bastante heterogêneo. O estudo comparativo realizado nesta dissertação é feito em duas abordagens. A primeira delas considera a complexidade assinto tica dos algoritmos de extração de vetores de características e das funções de distancia dos descritores...

‣ Studies on the salient properties of digital imagery that impact on human target acquisition and the implications for image measures.

Ewing, Gary John
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 3894012 bytes; 162675 bytes; application/pdf; application/pdf
Publicado em //1999 Português
Relevância na Pesquisa
344.9923%
Electronically displayed images are becoming increasingly important as an interface between man and information systems. Lengthy periods of intense observation are no longer unusual. There is a growing awareness that specific demands should be made on displayed images in order to achieve an optimum match with the perceptual properties of the human visual system. These demands may vary greatly, depending on the task for which the displayed image is to be used and the ambient conditions. Optimal image specifications are clearly not the same for a home TV, a radar signal monitor or an infrared targeting image display. There is, therefore, a growing need for means of objective measurement of image quality, where "image quality" is used in a very broad sense and is defined in the thesis, but includes any impact of image properties on human performance in relation to specified visual tasks. The aim of this thesis is to consolidate and comment on the image measure literatures, and to find through experiment the salient properties of electronically displayed real world complex imagery that impacts on human performance. These experiments were carried out for well specified visual tasks (of real relevance), and the appropriate application of image measures to this imagery...

‣ Generative models for image segmentation and representation

González Díaz, Iván
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Tese de Doutorado Formato: application/pdf
Português
Relevância na Pesquisa
344.42727%
This PhD. Thesis consists of two well differentiated parts, each of them focusing on one particular field of Computer Vision. The first part of the document considers the problem of automatically generating image segmentations in video sequences in the absence of any kind of semantic knowledge or labeled data. To that end, a blind spatio-temporal segmentation algorithm is proposed that fuses motion, color and spatial information to produce robust segmentations. The approach follows an iterative splitting process in which well known probabilistic techniques such as Gaussian Mixture Models are used as a core technique. At each iteration of the segmentation process, some regions are split into new ones, so that the number of mixture components is automatically set depending on the image content. Furthermore, in order to keep in memory valuable information from previous iterations, prior distributions are applied to the mixture components so that areas of the image that remain unchanged are fixed during the learning process. Additionally, in order to make decisions about whether or not to split regions at the end of one iteration, we propose the use of novel spatio-temporal mid-level features. These features model properties that are usually found in real-world objects so that the resulting segmentations are closer to the human perception. Examples of spatial mid-level features are regularity or adjacency...

‣ Time invariant steady-state Kalman filter for image super-resolution

Newland, C.; Gray, D.
Fonte: Image and Vision Computing New Zealand; New Zealand Publicador: Image and Vision Computing New Zealand; New Zealand
Tipo: Conference paper
Publicado em //2005 Português
Relevância na Pesquisa
438.3575%
The Kalman filter is usually considered to be too computationally infeasible for image super-resolution due to the size of the images and thus the state space involved. This paper presents a computationally feasible, simplified time invariant steady-state Kalman filter approach to image super-resolution for the case of constant translational camera motion between low-resolution frames. Quantitative and aesthetic comparisons are made to the maximum a-posteriori (MAP) super-resolution approach, considered to be one of the standard super-resolution techniques, to demonstrate the Kalman filter's superiority despite the steady-state assumption.; C. Newland and D. Gray

‣ Efficient methodologies for real-time image restoration

Samarasinghe, Devanarayanage Pradeepa
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
Português
Relevância na Pesquisa
345.20477%
In this thesis we investigate the problem of image restoration. The main focus of our research is to come up with novel algorithms and enhance existing techniques in order to deliver efficient and effective methodologies, applicable in real-time image restoration scenarios. Our research starts with a literature review, which identifies the gaps in existing techniques and helps us to come up with a novel classification on image restoration, which integrates and discusses more recent developments in the area of image restoration. With this novel classification, we identified three major areas which need our attention. The first developments relate to non-blind image restoration. The two mostly used techniques, namely deterministic linear algorithms and stochastic nonlinear algorithms are compared and contrasted. Under deterministic linear algorithms, we develop a class of more effective novel quadratic linear regularization models, which outperform the existing linear regularization models. In addition, by looking in a new perspective, we evaluate and compare the performance of deterministic and stochastic restoration algorithms and explore the validity of the performance claims made so far on those algorithms. Further, we critically challenge the ne- cessity of some complex mechanisms in Maximum A Posteriori (MAP) technique under stochastic image deconvolution algorithms. The next developments are focussed in blind image restoration...

‣ Design And Development of Mobile Image Overlay System For Image-Guided Interventions

ANAND, Manjunath
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
344.5906%
Numerous studies have demonstrated the potential efficacy of percutaneous image-guided interventions over open surgical interventions. The conventional image-guided procedures are limited by the freehand technique, requiring mental 3D registration and hand-eye coordination for needle placement. The outcomes of these procedures are associated with longer duration and increased patient discomfort with high radiation exposure. Previously, a static image overlay system was proposed for aiding needle interventions. Certain drawbacks associated with the static system limited the clinical translation. To overcome the ergonomic issues and longer calibration duration associated with static system, an adjustable image overlay system was proposed. The system consisted of monitor and semi-transparent mirror, attached together to an articulated mobile arm. The 90-degree mirror-monitor configuration was proposed to improve the physician access around the patient. MicronTracker was integrated for dynamic tracking of the patient and device. A novel method for auto-direct calibration of the virtual image overlay plane was proposed. Due to large mechanical structure, the precise movement was limited and consumed useful space in the procedure room. A mobile image overlay system with reduced system weight and smaller dimensions was proposed to eliminate the need for mechanical structure. A tablet computer and beamsplitter were used as the display device and mirror respectively. An image overlay visualization module of the 3D Slicer was developed to project the correct image slice upon the tablet device. The system weight was reduced to 1 kg and the image overlay plane tracking precision (0.11mm STD=0.05) was similar to the printed physical markers. The auto-calibration of the image overlay plane can be done in two simple steps...

‣ Anosognosia : imagem corporal na hemiplegia; Anosognosia: body image in hemiplegia

Thais Maria Albani Lovo
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 27/10/2006 Português
Relevância na Pesquisa
344.24492%
Pessoas portadoras de deficiência física podem sofrer algum tipo de alteração em sua imagem corporal. Os indivíduos com hemiplegia, pela perda motora e alterações de sensibilidade, em um lado do corpo podem sofrer alterações na imagem corporal, sejam elas temporárias ou definitivas. Para melhor conhecimento da imagem corporal na hemiplegia vimos a necessidade de desenvolver uma revisão de literatura sobre essas complexas e intrincadas relações. Relatamos conceitos e discussões a respeito de imagem corporal, com seus aspectos fisiológicos, afetivos ou libidinais e sociais, sobre a hemiplegia e a relação entre essa mudança corporal ocorrida devido à seqüela neurológica relacionada aos aspectos neurológicos como a anosognosia, aspectos afetivos e sociais da imagem corporal. A pesquisa bibliográfica foi realizada em bases de dados da Web Spirs, Web of Science, Bireme, Acervus ( Unicamp) e Cruesp, onde estão as bases como Medline, Sport discus, Psycinfo, Lilacs , Scielo, Biological Abstracts, Sociological Abstracts, entre outras. A escolha das respectivas bases foi feita após uma seleção entre as que dizem respeito a área de Ciências Biológicas e Ciências da Saúde. Nas bases foram selecionados os idiomas: Inglês...

‣ Perceptual Criteria on Image Compression

Moreno Escobar, Jesús Jaime
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2011 Português
Relevância na Pesquisa
345.94184%
Hoy en día las imágenes digitales son usadas en muchas areas de nuestra vida cotidiana, pero estas tienden a ser cada vez más grandes. Este incremento de información nos lleva al problema del almacenamiento de las mismas. Por ejemplo, es común que la representación de un pixel a color ocupe 24 bits, donde los canales rojo, verde y azul se almacenen en 8 bits. Por lo que, este tipo de pixeles en color pueden representar uno de los 224 ¼ 16:78 millones de colores. Así, una imagen de 512 £ 512 que representa con 24 bits un pixel ocupa 786,432 bytes. Es por ello que la compresión es importante. Una característica importante de la compresión de imágenes es que esta puede ser con per didas o sin ellas. Una imagen es aceptable siempre y cuando dichas perdidas en la información de la imagen no sean percibidas por el ojo. Esto es posible al asumir que una porción de esta información es redundante. La compresión de imágenes sin pérdidas es definida como deco dificar matemáticamente la misma imagen que fue codificada. En la compresión de imágenes con pérdidas se necesita identificar dos características: la redundancia y la irrelevancia de in formación. Así la compresión con pérdidas modifica los datos de la imagen de tal manera que cuando estos son codificados y decodificados...

‣ Optimization of Image Guided Radiation Therapy for Lung Cancer Using Limited-angle Projections

Zhang, You
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2015 Português
Relevância na Pesquisa
344.04008%

The developments of highly conformal and precise radiation therapy techniques promote the necessity of more accurate treatment target localization and tracking. On-board imaging techniques, especially the x-ray based techniques, have found a great popularity nowadays for on-board target localization and tracking. With an objective to improve the accuracy of on-board imaging for lung cancer patients, the dissertation work focuses on the investigations of using limited-angle on-board x-ray projections for image guidance. The limited-angle acquisition enables scan time and imaging dose reduction and improves the mechanical clearance of imaging.

First of all, the dissertation developed a phase-matched digital tomosynthesis (DTS) technique using limited-angle (<=30 deg) projections for lung tumor localization. This technique acquires the same traditional motion-blurred on-board DTS image as the 3D-DTS technique, but uses the planning 4D computed tomography (CT) to synthesize a phase-matched reference DTS to register with the on-board DTS for tumor localization. Of the 324 different scenarios simulated using the extended cardiac torso (XCAT) digital phantom, the phase-matched DTS technique localizes the 3D target position with an localization error of 1.07 mm (± 0.57 mm) (average ± standard deviation (S.D.)). Similarly...

‣ Parameterizing Image Quality of TOF versus Non-TOF PET as a Function of Body Size

Wilson, Joshua Mark
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2011 Português
Relevância na Pesquisa
344.04008%

Positron emission tomography (PET) is a nuclear medicine diagnostic imaging exam of metabolic processes in the body. Radiotracers, which consist of positron emitting radioisotopes and a molecular probe, are introduced into the body, emitted radiation is detected, and tomographic images are reconstructed. The primary clinical PET application is in oncology using a glucose analogue radiotracer, which is avidly taken up by some cancers.

It is well known that PET performance and image quality degrade as body size increases, and epidemiological studies over the past two decades show that the adult US population's body size has increased dramatically and continues to increase. Larger patients have more attenuating material that increases the number of emitted photons that are scattered or absorbed within the body. Thus, for a fixed amount of injected radioactivity and acquisition duration, the number of measured true coincidence events will decrease, and the background fractions will increase. Another size-related factor, independent of attenuation, is the volume throughout which the measured coincidence counts are distributed: for a fixed acquisition duration, as the body size increases, the counts are distributed over a larger area. This is true for both a fixed amount of radioactivity...

‣ Compressed Sensing Based Image Restoration Algorithm with Prior Information: Software and Hardware Implementations for Image Guided Therapy

Jian, Yuchuan
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2012 Português
Relevância na Pesquisa
344.04008%

Based on the compressed sensing theorem, we present the integrated software and hardware platform for developing a total-variation based image restoration algorithm by applying prior image information and free-form deformation fields for image guided therapy. The core algorithm we developed solves the image restoration problem for handling missing structures in one image set with prior information, and it enhances the quality of the image and the anatomical information of the volume of the on-board computed tomographic (CT) with limited-angle projections. Through the use of the algorithm, prior anatomical CT scans were used to provide additional information to help reduce radiation doses associated with the improved quality of the image volume produced by on-board Cone-Beam CT, thus reducing the total radiation doses that patients receive and removing distortion artifacts in 3D Digital Tomosynthesis (DTS) and 4D-DTS. The proposed restoration algorithm enables the enhanced resolution of temporal image and provides more anatomical information than conventional reconstructed images.

The performance of the algorithm was determined and evaluated by two built-in parameters in the algorithm, i.e., B-spline resolution and the regularization factor. These parameters can be adjusted to meet different requirements in different imaging applications. Adjustments also can determine the flexibility and accuracy during the restoration of images. Preliminary results have been generated to evaluate the image similarity and deformation effect for phantoms and real patient's case using shifting deformation window. We incorporated a graphics processing unit (GPU) and visualization interface into the calculation platform...

‣ Spectral image utility for target detection applications

Stefanou, Marcus S.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Dissertação
Português
Relevância na Pesquisa
345.29836%
In a wide range of applications, images convey useful information about scenes. The “utility” of an image is defined with reference to the specific task that an observer seeks to accomplish, and differs from the “fidelity” of the image, which seeks to capture the ability of the image to represent the true nature of the scene. In remote sensing of the earth, various means of characterizing the utility of satellite and airborne imagery have evolved over the years. Recent advances in the imaging modality of spectral imaging have enabled synoptic views of the earth at many finely sampled wavelengths over a broad spectral band. These advances challenge the ability of traditional earth observation image utility metrics to describe the rich information content of spectral images. Traditional approaches to image utility that are based on overhead panchromatic image interpretability by a human observer are not applicable to spectral imagery, which requires automated processing. This research establishes the context for spectral image utility by reviewing traditional approaches and current methods for describing spectral image utility. It proposes a new approach to assessing and predicting spectral image utility for the specific application of target detection. We develop a novel approach to assessing the utility of any spectral image using the target-implant method. This method is not limited by the requirements of traditional target detection performance assessment...

‣ Content-based image retrieval and its benefits for the stock photography market

Padeste, Romano
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
345.10312%
The development of powerful low-cost desktop computer systems has changed the pre-press business where tight deadlines must be met per sistently. An increasing number of newspapers and magazines are acquiring, handling, and storing images digitally while the use of hardcopies and slides decreases. Today's computers and high capacity storage-media enable stock pho tography agencies to build digital image databases, giving users fast access to large numbers of images. However, the transition from analog to digital image archives imposes new problems: with thousands of images at hand, the search for a particular image may turn into the search for the needle in a haystack. The first image Database Management Systems (DBMSs) were extended text DBMSs, which stored the image data along with a set of manually entered descriptive keywords. The major problem with this approach is that there is no generally agreed-upon language to describe images. Even sophis ticated DBMSs are unable to detect synonyms; hence, an image described with certain properties such as "curvy" may not be found if a user enters "wavy" as a search criterion. Furthermore, some image properties are hard to describe with keywords. A search is likely to fail if properties were not described at the database population stage when images are added to the database. Finally...

‣ Retrieval from an image knowledge base

Janicki, James
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
344.04008%
With advances in computer technology, images and image databases are becoming increasingly important. Retrievals of images in current image database systems have been designed using keyword searches. These carefully designed and handcrafted systems are very efficient given the application domain they are built for. Unfortunately, they are not adaptable to other domains, not expandable for other uses of the existing information and are not very forgiving to their users. The appearance of full-text search provides for a more general search given textual documents. However, pictorial images contain a vast amount of information that is difficult to catalog in a general way. Further this classification needs to be dynamic providing for flexible searching capability. The searching should allow for more than a pre-programmed set of search parameters, as exact searches make the image database quite useless for a search that was not designed into the original database. Further the incorporation of knowledge along with the images is difficult. Development of an image knowledge base along with content-based retrieval techniques is the focus of this thesis. Using an artificial intelligence technique called case-based reasoning, images can be retrieved with a degree of flexibility. Each image would be classified by user entered attributes about the image called descriptors. These descriptors would also have a "degree-of-importance" parameter. This parameter would indicate the relative importance or certainty of that descriptor. These descriptors are collected as the "case" for the image and stored in "frames" Each image can vary as to the amount of attribute information they contain. Retrieval of an image from the knowledge base begins with the entry of new descriptors for the desired image. Along with the descriptors are the degree-of-importance parameter. The degree-of-importance would indicate the requirement for the desired image to match that descriptor. Again...

‣ Designing pictorial stimuli for perceptual image difference experiments

Farnand, Susan
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Dissertação
Português
Relevância na Pesquisa
344.24492%
Imaging system development often involves impact assessment of design choices. For systems that generate images for human consumption, such as cameras and displays, the effect of design decisions are often evaluated using `real-world' images. System changes can have complicated effects on pictorial images that do not, as yet, have specified instrumental measurement methods. Consequently, human observers are often used in image quality assessment. However, human observers can react differently to complex pictorial stimuli both between observers and for a single observer over the course of a lengthy experiment. In an experimental setting, pictorial scenes present a greater opportunity than do uniform patches for observers' individual differences to significantly impact the process. This study was conducted to increase the understanding of the optimal design of pictorial stimuli for more effective and efficient perceptual experiments. The goals of this dissertation were to: 1. Understand the impact of image content on visual attention and the consistency of image comparison experimental results 2. Understand how visual attention changes with successive viewing of pictorial images 3. Apply this understanding to develop guidelines for pictorial target design for perceptual image comparison experiments To achieve these objectives...

‣ Perceived image contrast and observer preference: I. The effects of lightness, chroma, and sharpness manipulations on contrast perception

Calabria, Anthony; Fairchild, Mark
Fonte: The Society for Imaging Science and Technology (IS&T) Publicador: The Society for Imaging Science and Technology (IS&T)
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
344.24492%
A large-scale investigation into the perception of contrast in color images was performed. Psychophysical experiments were performed to determine the influence of image lightness, chroma, and sharpness transforms on perceived image contrast and observer preference. The influence of these transforms on perceived contrast was investigated separately by independent soft copy, paired comparison tests of contrast perception and image preference. The perception of contrast across transformations was also investigated, as was the perception of image contrast relative to the most preferred image manipulation. In all, four experiments of contrast perception and image preference were performed by at least thirty-two observers each. Results of the lightness, chroma, and sharpness-contrast experiments indicate perceived image contrast is a function of multiple image characteristics as opposed to simply being a function of the dynamic range of image intensity. In the lightness-contrast experiments, images of identical white and black points were scaled to have significant differences in contrast based on their manipulations from the original image. In the chroma-contrast experiments, images of identical lightness channels were scaled to have significant differences in perceived contrast due to relative chroma amount. In the sharpness-contrast experiments...

‣ Perceived image contrast and observer preference: II. empirical modeling of perceived image contrast and observer preference data

Calabria, Anthony; Fairchild, Mark
Fonte: The Society for Imaging Science and Technology (IS&T) Publicador: The Society for Imaging Science and Technology (IS&T)
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
346.1435%
Psychophysical experimentation was performed on the perceived contrast of color images and its effect on observer preference. Goals of this research included the following: investigation into the roles of image lightness, chroma and sharpness manipulations on perceived image contrast; modeling the perception of image contrast with physical image parameters; the relation of perceived contrast of an image to the most preferred version of that image; and the generation of a large scale image contrast data set for later use in image difference/quality metric development. These goals were undertaken by administration of soft copy paired-comparison experiments of perceived image contrast and observer preference. These tests were performed over four months, by more than seventy observers. Perceived image contrast was determined to be scalable with respect to lightness, chroma, and sharpness manipulations. Perceived image contrast scales were image independent between five pictorial images. Significant contrast differences between images of identical white and black points were perceived, demonstrating that image white and black points do not solely determine image contrast. Significant image contrast differences were found between full color images and their achromatic versions...