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1
Content available remote A novel brightness preserving joint histogram equalization technique for contrast enhancement of brain MR images
Mishro Pranaba K, Agrawal Sanjay, Panda Rutuparna, Abraham Ajith
Biocybernetics and Biomedical Engineering
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2021
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Vol. 41, no. 2
540--553
EN
Low contrast is a challenging factor in brain magnetic resonance (MR) images due to its structural complexity. Histogram equalization (HE) approach is often used in enhancing the contrast in brain MR images. However, the spatial information is not taken into account in this approach. Further, the problem of preserving structural details while retaining the brightness is also an important concern. To solve these, we suggest a novel stationary wavelet transform based brightness preserving joint histogram equalization (SWT-BPJHE) scheme for brain MR image contrast enhancement. Our contributions are – i) use of SWT to extract the low sub-band wavelength coefficients from the low contrast input image for enhancement, ii) to isolate the high frequency wavelength coefficients from enhancement, retaining the structural details, iii) to preserve brightness. The suggested scheme is experimented with synthetic brain MR images from BrainWeb and clinical images from Howard Whole Atlas databases. The performance is evaluated in terms of several validation indices followed by statistical analysis. The outcomes reveal the superiority of the suggested scheme in comparison to state-of-the-art methods.
2
Content available remote A hybrid feature preservation technique based on luminosity and edge based contrast enhancement in color fundus images
Palanisamy Gopinath, Shankar Natarajan B., Ponnusamy Palanisamy, Gopi Varun P.
Biocybernetics and Biomedical Engineering
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2020
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Vol. 40, no. 2
752--763
EN
Color fundus image analysis for detecting the retinal abnormalities requires an improved visualization of image attributes with sufficient luminosity, contrast and accurate edge details. A hybrid technique based on singular value equalization using shearlet transform and adaptive gamma correction, followed by contrast limited adaptive histogram equalization (CLAHE) is proposed for the enhancement of luminosity and contrast in color fundus images. The low frequency components of the original and adaptive gamma transformed value channel in HSV color space obtained by applying shearlet transform are considered for singular value equalization. The high frequency components of the unchanged value channel, denoised using soft thresholding are applied while performing inverse shearlet transform. Luminosity component in Lab colorspace is considered for performing CLAHE on the singular value equalized image. Subjective analysis is done based on visualization of the image attributes and the objective analysis is carried out based on the parameters such as Peak signal to noise ratio, entropy, feature similarity index, edge-based contrast measure, quality index and noise suppression measure. The simulation results evince superior noise performance, sufficient luminosity adjustment and improved contrast along with excellent edge detail preservation when compared with the existing state-of-the-art techniques.
3
Content available Problem of the objects detection on low quality 3D image – example solution
Gądek-Moszczak A.
Zeszyty Naukowe. Quality. Production. Improvement
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2017
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No. 1 (6)
134--141
EN
Precise detection of analyzed objects is crucial and the most important task in quantitative and qualitative image of the microstructure analysis. The most common image distortion is noise, artefacts and low contrast. In the paper, author on the example of poor quality image of the polyurethane-polystyren composite structure, obtained with the X-ray microtomograph, presented possible methods of noise reduction, contrast enhancement, and correction of detection errors on the binary image.
4
Content available Adaptacyjna metoda poprawy kontrastu dla cyfrowych obrazów rozmazów cytologicznych
Oszutowska-Mazurek D. A., Waker-Wójciuk G, Sycz K.
Problemy Nauk Stosowanych
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2016
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T. 5
163--170
PL
Wstęp i cel: Zwiększenie kontrastu między jądrem komórkowym a cytoplazmą zapewnia poprawę wizualizacji cytologicznych cech komórki. Celem pracy jest poprawa wizualizacji jądra komórkowego. Materiał i metody: Automatyzacja doboru progu z wykorzystaniem algorytmu adaptacyjnego progowania dla rozkładów dwumodalnych została przeprowadzona dla obrazów rozmazów cytologicznych. Wyniki: Uzyskano zwiększony kontrast dla jądra komórkowego, dzięki czemu osiągnięto poprawę wizualizacji struktury chromatyny. Wniosek: Adaptacyjna metoda poprawy kontrastu może być użyteczna w diagnostyce cytologicznej, ale potrzebna jest weryfikacja w oparciu o większą bazę danych obrazów cytologicznych.
EN
Introduction and aim: Contrast enhancement between nucleus and cytoplasm ensures improvement of cytological features visualisation. The aim of study is improvement of nucleus visualisation. Material and methods: Automation of threshold estimation with the use of adaptive tresholding algorithm for bimodal distributions was provided for images of cytological smears. Results: Improved contrast for cell nuclei was obtained and therefore the enhancement of chromatine structure visualisation is achieved. Conclusion: Adaptive method of contrast enhancement could be useful in cytological diagnosis, but requires verification with the use of large database of cytological images.
5
Content available Comparison of global methods for the image contrast enhancement based on biometric images
Smorawa D., Kubanek M.
Journal of Applied Mathematics and Computational Mechanics
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2016
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Vol. 15, nr 2
137--146
EN
This work presents the methods of improvement of biometric images contrast, and it corresponds to one of the main parts of the biometric system that verify identities based on distribution of the blood vessels in a hand. The acquisition of the palm blood vessel pattern causes noises that can prevent the right verification. To solve this problem, we investigate four different methods of contrast enhancement, and provide an evaluation of their performance by using four different quantitative contrast measurement methods.
6
Content available remote Automatyczne wykrywanie osób w nagraniach uzyskanych przy niedostatecznym oświetleniu
Konieczka A., Chmielewska A., Balcerek J.
Przegląd Elektrotechniczny
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2015
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R. 91, nr 9
101-104
PL
Artykuł przedstawia system do detekcji osób na nagraniach pochodzących z monitoringu miejskiego na otwartej przestrzeni. Proponowany system został przetestowany w trudnych, nocnych warunkach oświetlenia. W celu polepszenia jakości zarejestrowanych sekwencji wideo zaproponowano algorytm lokalnej poprawy kontrastu. Dzięki niemu detekcja obiektów ruchomych za pomocą GMM (Gaussian mixture model) oraz analizy BLOB (binary large object) jest bardziej precyzyjna. Dodatkowo ruchome obiekty wykryte w obrazie binarnym są śledzone przy użyciu filtru Kalmana, co zwiększa skuteczność algorytmu wykrywającego osoby. W artykule omówiono również dobór parametrów programu oraz sposób akwizycji obrazów.
EN
The article presents the issue related to the intelligent analysis of video sequences, which are obtained from the city monitoring. Analysis of people detection, who passed under the camera in the outdoor scenes, has been tested in low lighting conditions (during the night). In order to improve the quality of acquired video sequences, local contrast enhancement algorithm was used. Thanks to this, detection of moving objects with the use of the GMM (Gausian mixture model) and BLOB (binary large object) analysis is more precise. In addition, detected moving objects in the binary image are tracked with the use of Kalman filter, which increases the efficiency of people detection. Selection of algorithm parameters and video acquisition method were also discussed.
7
Content available Porównanie wybranych miar kontrastu obrazów achromatycznych
Bal A.
Pomiary Automatyka Kontrola
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2010
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R. 56, nr 11
1359-1353
PL
W pracy poruszono zagadnienie oceny kontrastu achromatycznych obrazów cyfrowych. Przedstawiono porównanie wyników oceny kontrastu obrazów przy wykorzystaniu, zarówno znanych z literatury jak i nowych, miar kontrastu. Zaproponowane nowe miary bazują na lokalnej realizacji pewnych znanych z literatury globalnych miar kontrastu. Badania przeprowadzono dla kilkudziesięciu obrazów testowych. Przedstawiono także problemy związane z doborem miar kontrastu do danego zastosowania.
EN
The paper deals with the problem of gray level image contrast evaluation. Comparison of several, both known from the literature and new, image contras evaluation methods are presented. Methods taken into consideration are: (1) and (2)-two methods based on Weber-Fechner law, (3) and (4)-variance based methods, method (5) with its modifications-based on difference between gray-level values of neighboring pixels, (6)-image energy based method, (7)- method based on Shannon entropy information theory, (8)-(11)-group of new methods based on the idea of aggregating of local contrast evaluation value obtained for neighborhood of pixel for all pixels in image. The comparison was performed on the set of 48 test images obtained as a result of contrast enhancement of 8 images (Fig. 1) using 5 contrast enhancement methods. The results of contrast evaluation of all images are given in Table 1. In order to compare the numerical contrast evaluation with visual judgment, two subsets of test images are presented (Figs. 2 and 3) together with charts of the contrast values (Fig. 4). The obtained results are analysed in Section 4, where on the example of two different applications of contrast enhancement the difficulties with contrast evaluation and selection of the best contrast evaluation method are discussed. It is not possible to choose the best contrast evaluation method basing on the obtained results and taking into consideration different purposes of image contrast enhancement. Because of this, a contrast evaluation method should be chosen for each application individually.
8
Content available Porównanie wybranych metod oceny kontrastu achromatycznych obrazów cyfrowych
Bal A.
Pomiary Automatyka Kontrola
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2009
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R. 55, nr 7
501-503
PL
Praca dotyczy zagadnienia oceny kontrastu achromatycznych obrazów cyfrowych. Przedstawiono i porównano znane z literatury metody oceny kontrastu obrazów, a także zaproponowano nowe rozwiązania bazujące na określeniu różnic poziomów szarości sąsiadujących ze sobą pikseli. Ocena przydatności poszczególnych metod została dokonana na przykładzie zadania wyboru najlepszej wersji obrazu pod kątem jego dalszej analizy. Przeprowadzona analiza wyników oceny kontrastu obrazów wskazuje, że dla przyjętych warunków porównania najlepszą metodą oceny kontrastu jest jedna z nowych metod.
EN
This paper deals with the gray-level image contrast evaluation problem. In the paper some methods of contrast evaluation are considered, namely: (1) and (2) - two methods based on Weber-Fechner law ((2) is a Michelson contrast), next two methods (3) and (4) are based on variance of gray-level values in the image, and the last two (5) and (6) are new methods in which the difference between gray-level values of neighbouring pixels is used for calculating the image contrast ratio. The evaluation of the described methods has been made for one of the standard usage cases of the contrast evaluation method, i.e. evaluation of images after contrast enhancement for choosing the best of them for its visual analysis. The investigations have been performed on the example of aerial image AERIAL (Fig. 1). The contrast enhancement of this image gives the set of test images (a)-(j) (Fig. 1). Table 1 presents the contrast enhancement methods and their parameters used for obtaining test images. The contrasts evaluation values of the test images obtained by use of the methods (1)-(6) are given in Table 2. Table 3 shows the ranking of the images (a)-(j) obtained by sorting in descending order the contrast ratio of test images independently for each evaluation method. It is difficult to indicate the best evaluation method but it seems that, basing on the comparison, the new method (5) is the best image contrast evaluation method
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