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1

Contrast enhancement of scanning electron microscopy images using a noncomplex multiphase algorithm

Alsaygh Zaid, Al-Ameen Zohair

Applied Computer Science

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2022

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Vol. 18, no 2

28--42

EN

Microscopic technology has recently flourished, allowing unparalleled viewing of microscopic elements invisible to the normal eye. Still, the existence of unavoidable constraints led on many occasions to have low contrast scanning electron microscopic (SEM) images. Thus, a noncomplex multiphase (NM) algorithm is proposed in this study to provide better contrast for various SEM images. The developed algorithm contains the following stages: first, the intensities of the degraded image are modified using a two-step regularization procedure. Next, a gamma-corrected cumulative distribution function of the logarithmic uniform distribution approach is applied for contrast enhancement. Finally, an automated histogram expansion technique is used to redistribute the pixels of the image properly. The NM algorithm is applied to natural-contrast distorted SEM images, as well as its results are compared with six algorithms with different processing notions. To assess the quality of images, three modern metrics are utilized, in that each metric measures the quality based on unique aspects. Extensive appraisals revealed the adequate processing abilities of the NM algorithm, as it can process many images suitably and its performances outperformed many available contrast enhancement algorithms in different aspects.

2

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.

3

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.

4

Automatic contrast enhancement of brain MR images using Average Intensity Replacement based on Adaptive Histogram Equalization (AIR-AHE)

Isa I. S., Sulaiman S. N., Mustapha M., Karim N. K. A.

Biocybernetics and Biomedical Engineering

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2017

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Vol. 37, no. 1

24--34

EN

Medical imaging is the most established technique of visualizing the interior of the human body without the risk of the non-invasive effect. This technology is designed to produce images, and it is also capable of representing information about the screening location. In MRI imaging, the poor image quality particularly the low contrast image may provide insufficient data for the visual interpretation of such affected locations. Therefore, the need of image enhancement arises to improve image visions and also to computationally support the image processing technique. In general, conventional contrast enhancement methods may work well for some images. However, in MRI brain image, there are often more complex situations where the WMH signal is high but it may mistakenly be considered as other brain tissues such as CSF. With the motivation to classify the most possible WMH regions, this paper proposes a novel image contrast algorithm of WMH enhancement for MRI image. This algorithm is also known as the Average Intensity Replacement – Adaptive Histogram Equalization (AIR-AHE). The proposed algorithm is applied to the FLAIR image based on the intensity adjustment and contrast mapping techniques. The proposed algorithm for the image enhancement is superior to the existing methods by using image evaluation quantitative methods of PSNR, average gradient values and MSE. Furthermore, the edge information pertaining to the potential WMH regions can effectively increase the accuracy of the results.

5

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.

6

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.

7

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.

8

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.

9

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

10

Wykorzystanie metod kontrastu lokalnego do wykrywania krawędzi w obrazie

Vorobel R., Stobińska M., Przybyszewski K.

Automatyka / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

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2009

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T. 13, z. 3/1

1033-1041

PL

Wykorzystując metody kontrastu lokalnego, zdefiniowaliśmy prostą metodę wykrywania krawędzi, charakteryzującą się zwiększoną czułością względem poziomu różnicy jasności. Umożliwia ona wykrycie krawędzi, gdy różnica jasności jest minimalna, ze względu na zwiększona czułość metody obliczania pochodnej wykorzystującej różnice względne. Opisaną metodę wykrywania krawędzi możemy stosować w bardziej skomplikowanych obliczeniowo metodach wykrywania krawędzi, jaką jest na przykład metoda Canny'ego, zamiast metody Sobela. Stwarza to nowe możliwości zwiększenia precyzyjności metod wykrywania krawędzi.

EN

A simple method of edges detection have been described. It is based on the method of local contrast enhancement and it is distinguished by increased sensitivity of the brightness difference. It enables the edges detection even for a minimal brightness difference because of a more sensitivity method of the derivative calculations based on the relative differences between brightness levels. It is possible to use that method instead another ones, as Stobel's one for example, in more complicated calculations, as Canny's method, for example. These create a new possibility to increase a sensitivity of the edges detection methods.

11

Uogólniona lokalna metoda poprawy kontrastu obrazów cyfrowych

Bal A.

Zeszyty Naukowe. Automatyka / Politechnika Śląska

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2008

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z. 150

121-127

PL

Praca dotyczy zagadnienia poprawy kontrastu achromatycznych obrazów cyfrowych. Na tle prezentowanych w literaturze metod poprawy kontrastu obrazów przedstawiono ważoną lokalną metodę poprawy kontrastu będącą uogólnieniem pewnej klasy znanych lokalnych metod poprawy kontrastu.

EN

In this paper the problem of contrast enhancement of gray-level images is analyzed. On the background of the methods described in literature novel weighted local contrast enhancement method, which is a generalization of a certain class of local contrast enhancement method, is presented.

12

Wzmacnianie kontrastu obrazu jako jeden ze sposobów poprawy jego jakości

Vorobel R., Przybyszewski K.

Automatyka / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

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2008

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T. 12, z. 3

723-731

PL

W pracy przedstawiono analizę znanych podejść do poprawy jakości obrazów przez wzmacnianie ich kontrastu z wykorzystaniem przekształceń globalnych poziomów jakości. Autorzy zaproponowali oryginalną metodę dwuparametrycznego przetwarzania poziomów jasności obrazu, która wykorzystuje do obliczeń kontrastu elementu obrazu poziom subiektywnej adaptacji obserwatora do jasności. W połączeniu z metodami wzmacniania kontrastu lokalnego zapewnia ona poprawę jakości obrazu. Efektywność metod została zilustrowana przykładami.

EN

The analysis of known approaches to image quality enhancement with contrast amplification by global transformation is carried out. The original biparametric method for image gray level transformation, which uses pixel contrast evaluation with respect to fixed adaptation gray level, has been proposed. In association with local contrast transformation it provides image quality enhancement. The effectiveness of proposed approach is illustrated with examples.

13

Helmet mounted display based system for stereoscopic visualization supporting inner ear operation

Kucharski T., Kujawińska M., Leśniewski M., Niemczyk K., Bruzgielewicz A.

Elektronika : konstrukcje, technologie, zastosowania

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2004

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Vol. 45, nr 8-9

120-122

EN

In this paper authors present a system consisting of operational stereoscopic microscope with two image acquisition channels, data processing unit and Helmet Mounted Display (HMD) for stereoscopic of visualization field. Special attention is paid to the development of automatic image low contrast enhancement. The algorithms are optimized for stereo visualization of biological micro-structures of inner ear. Some of those structures have quasi-phase nature and are almost invisible by human eye. The tests performed at the images captured during operation have been positively evaluated by surgeons. The performance of the system presented ascertained that quality of inner ear processed images guaranties safety carrying of operations not undertaken so far.

PL

Autorzy prezentują system zawierający operacyjny mikroskop stereoskopowy obsługujący dwa kanały rejestrujące, program przetwarzający dane oraz hełm optyczny (HMD) służący do stereoskopowej wizualizacji wzbogaconego obrazu pola operacyjnego. W pracy poświęcono uwagę wzbogaceniu obrazu oryginalnego tkanek ucha wewnętrznego. Tkanki te posiadają quasi-fazową naturę i są trudno rozróżnialne przez ludzkie zmysły. Testy przeprowadzone podczas operacji zostały pozytywnie ocenione przez chirurgów. Projekt udowodnił, że jakość przetworzonych umożliwia podjąć się operacji zaniechanych jak dotąd.