Butterworth equations for homomorphic filtering of images

Adelmann, Holger G.

doi:10.1016/s0010-4825(98)00004-3

Cited by 95 publications

(37 citation statements)

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“…The apical-most and the basal-most slices of each stack were selected for analysis. For image enhancement as well as spatial measurements, Image Pro Plus software was used (version 4.5; Media Cybernatics, Crofton, Md., USA) which was additionally equipped with a Gaussian filter module [Adelmann, 1997] and a homomorphic filter plugin [Adelmann, 1998]. Adobe Photoshop software (version 7.0; Adobe Systems, San Jose, Calif., USA) was used for the arrangement of RGB-color images out of single grey scale images each representing the signal of one color channel.…”

Section: Laser Confocal Imaging Image Analysis and Processingmentioning

confidence: 99%

Human Uterine Epithelial RL95-2 Cells Reorganize Their Cytoplasmic Architecture with Respect to Rho Protein and F-Actin in Response to Trophoblast Binding

Heneweer

Adelmann

Kruse

et al. 2003

Cells Tissues Organs

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Embryo implantation is initiated by interaction of trophoblast with uterine epithelium via the apical cell poles of both partners. Using spheroids of human trophoblastoid JAR cells and monolayers of human uterine epithelial RL95-2 cells to simulate this initial interaction, we previously demonstrated that formation of stable cell-to-cell bonds depends on actin cytoskeleton (F-actin) and small GTPases of the Rho family, most likely RhoA. In this study, we determined the apical as well as the basal distribution of these proteins by fluorescence confocal microscopy before and after binding of JAR spheroids. We focussed on changes in cytoplasmic organization with respect to apicobasal polarity of RL95-2 cells. Before binding of spheroids, significantly higher fluorescence signals of RhoA [37 ± 6 grey scale values (gsv)] and of F-actin (41 ± 3 gsv) were found in the basal region of RL95-2 cells as compared to the apical pole (RhoA: 24 ± 3 gsv, F-actin: 28 ± 2 gsv). After binding of JAR spheroids, this apicobasal asymmetry was inverted (RhoA: 55 ± 10 gsv apical vs. 25 ± 3 gsv basal; F-actin: 108 ± 17 gsv apical vs. 57 ± 7 gsv basal). Inactivation of Rho GTPases in RL95-2 cells by Clostridium difficile toxin A leads to a loss of their apical adhesion competence, as previously published. Here, we observed a uniform distribution of RhoA and F-actin between apical and basal region rather than an asymmetric one in toxin A-treated cells. These data suggest that activation of Rho GTPases and coordinated rearrangement of F-actin within uterine epithelial cells in response to trophoblast binding are part of a generalized structural and functional reorganization of the cytoplasm. This involves not only the immediate contact zone (apical) but also the opposite (basal) cell pole and may be a critical element of uterine epithelial reactions during transition between trophoblast adhesion and transmigration.

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Section: Laser Confocal Imaging Image Analysis and Processingmentioning

confidence: 99%

Human Uterine Epithelial RL95-2 Cells Reorganize Their Cytoplasmic Architecture with Respect to Rho Protein and F-Actin in Response to Trophoblast Binding

Heneweer

Adelmann

Kruse

et al. 2003

Cells Tissues Organs

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“…When surfaces are covered by haze or thin clouds, the illuminated components represent the solar radiation reflected by haze and the reflected components represent the solar radiation reflected by the planetary surface. The simplified concept is shown as follow (Fan and Zhang, 2011;Adelmann, 1998).…”

Section: Hf Algorithmmentioning

confidence: 99%

“…Generally, the image-based haze removal technique can be grouped into two algorithms：1) spatial filtering (i.e. wavelet analysis (Du et al, 2002), the homomorphic filtering (HF) (Fan and Zhang, 2011;Adelmann, 1998), and the improved HF (Cai et al, 2011)); 2) spectral transformation (i.e. Tasseled Cap (TC) transformation (Richter, 1996), haze optimized transformation (HOT) (Zhang et al, 2002), and advanced thin cloud optimized transformation (AHOT) (He et al, 2010;Liu et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

A Comparison of Haze Removal Algorithms and Their Impacts on Classification Accuracy for Landsat Imagery

et al. 2017

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Abstract:The quality of Landsat images in humid areas is considerably degraded by haze in terms of their spectral response pattern, which limits the possibility of their application in using visible and near-infrared bands. A variety of haze removal algorithms have been proposed to correct these unsatisfactory illumination effects caused by the haze contamination. The purpose of this study was to illustrate the difference of two major algorithms (the improved homomorphic filtering (HF) and the virtual cloud point (VCP)) for their effectiveness in solving spatially varying haze contamination, and to evaluate the impacts of haze removal on land cover classification. A case study with exploiting large quantities of Landsat TM images and climates (clear and haze) in the most humid areas in China proved that these haze removal algorithms both perform well in processing Landsat images contaminated by haze. The outcome of the application of VCP appears to be more similar to the reference images compared to HF. Moreover, the Landsat image with VCP haze removal can improve the classification accuracy effectively in comparison to that without haze removal, especially in the cloudy contaminated area. Keywords: haze contamination; HF; VCP; classification accuracy Resumo:A qualidade de imagens Landsat em áreas úmidas é consideravelmente degradada pela neblina em termos do seu padrão de resposta espectral, o que limita a possibilidade da sua aplicação usando as bandas do visível e infravermelho próximo. Uma variedade de algoritmos de remoção de neblina têm sido propostos para corrigir estes efeitos indesejados da iluminação, causados pela contaminação por neblina. O propósito deste estudo foi demonstrar a diferença entre os dois principais algoritmos (a filtragem homomórfica melhorada (HF) e a nuvem virtual de pontos (VCP)), considerando sua efetividade na solução da contaminação da neblina com variação espacial, e para avaliar os impactos da remoção da neblina na classificação da cobertura do solo. Um estudo de caso com utilização de grande quantidade de imagens Landsat TM e climáticas (claras e com neblina) em áreas muito úmidas da China comprovou que estes algoritmos de remoção têm bom desempenho no processamento das imagens contaminadas por neblina. O resultado da aplicação do filtro VCP parece ser mais similar às imagens de referência quando comparado ao filtro HF. Além disso, a imagem Landsat com a remoção de neblina por VCP pode efetivamente melhorar a acurácia da classificação em comparação àquelas sem a remoção da neblina, especialmente em áreas contaminadas por nuvens. Palavras-chave:Contaminação por neblina; HF; VCP; Acurácia da classificação.

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“…Homomorphic Filtering [12,13] improves brightness and contrast by modifying an image's illumination based on the assumption than an image's illumination varies slowly and that reflectance varies rapidly. It computes the Fast Fourier Transform (FFT) of an image's element-wise logarithm and then does high pass filtering to preserve reflectance while normalizing low-frequency brightness information.…”

Section: Homomorphic Filteringmentioning

confidence: 99%

Color Constancy Algorithms for Object and Face Recognition

Kanan

Flores

Cottrell

2010

Advances in Visual Computing

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Abstract. Brightness and color constancy is a fundamental problem faced in computer vision and by our own visual system. We easily recognize objects despite changes in illumination, but without a mechanism to cope with this, many object and face recognition systems perform poorly. In this paper we compare approaches in computer vision and computational neuroscience for inducing brightness and color constancy based on their ability to improve recognition. We analyze the relative performance of the algorithms on the AR face and ALOI datasets using both a SIFT-based recognition system and a simple pixel-based approach. Quantitative results demonstrate that color constancy methods can significantly improve classification accuracy. We also evaluate the approaches on the Caltech-101 dataset to determine how these algorithms affect performance under relatively normal illumination conditions.

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Butterworth equations for homomorphic filtering of images

Cited by 95 publications

References 1 publication

Human Uterine Epithelial RL95-2 Cells Reorganize Their Cytoplasmic Architecture with Respect to Rho Protein and F-Actin in Response to Trophoblast Binding

Human Uterine Epithelial RL95-2 Cells Reorganize Their Cytoplasmic Architecture with Respect to Rho Protein and F-Actin in Response to Trophoblast Binding

A Comparison of Haze Removal Algorithms and Their Impacts on Classification Accuracy for Landsat Imagery

Color Constancy Algorithms for Object and Face Recognition

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