Original Brightness Research Articles

Contrast limited fuzzy adaptive histogram equalization for enhancement of brain images

ABSTRACTContrast limited fuzzy adaptive histogram equalization (CLFAHE) is proposed to improve the contrast of MRI Brain images. The proposed method consists of three stages. First, the gray level intensities are transformed into membership plane and membership plane is modified with Contrast intensification operator. In the second stage, the contrast limited adaptive histogram equalization is applied to the modified membership plane to prevent excessive enhancement in contrast by preserving the original brightness. Finally, membership plane is mapped back to the gray level intensities. The performance of proposed method is evaluated and compared with the existing methods in terms of qualitative measures such as entropy, PSNR, AMBE, and FSIM. The proposed method provides enhanced results by giving better contrast enhancement and preserving the local information of the original image. © 2017 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 27, 98–103, 2017

Proporciones, alegorías, ángeles músicos y ejecución históricamente informada en los órganos de la catedral de México

Análisis estético de las cajas gemelas de los órganos de la Catedral de México. Correspondencia entre las proporciones arquitectónicas del barroco y las proporciones aritmético-musicales pitagóricas. La composición fónica de un retablo sonoro. Los cuerpos de flautados de fachada, los ecos internos, los flautados de nave y la trompetería horizontal. La expresión sonora de las calles, platabandas, cornisas y ventanas de las cajas de cedro y ayacahuite de los órganos de Catedral. Los dorados y rubicundos ángeles en instrumentos mudos. Iconografía organológica. Instrumentos prehispánicos, clásicos grecolatinos, góticos, renacentistas y barrocos; un despliegue enciclopédico. Disposición actual de los registros. Diseños de ambas fachadas.
 La composición original de los tubos. Resultado lumínico y cromático. Restauración del brillo original y de los figurones pintados en las bocas de las flautas de fachada. 
 Documentos en que debe apoyarse toda restauración; mantenimiento y cuidado para que estando en uso no se deteriore. Preservación y promoción del archivo musical de catedral. Función social y sentido cultural al restaurar un instrumento patrimonial único. 
 Uso litúrgico y académico para preservar y promover la cultura organística.
 El instrumento como fuente de investigación; la Ejecución Históricamente Informada (EHI).

An Improved Cuckoo Search based Optimal Ranged Brightness Preserved Histogram Equalization and Contrast Stretching Method

This paper is organized into two main parts. In the first part, two methods have been discussed to preserve the original brightness of the image which are Parameterized transformation function and a novel variant of modified Histogram Equalization (HE) method. In this study both methods have been formulated as optimization problems to increase the efficiency of the corresponding methods within reasonable time. In the second part, a novel modified version of Cuckoo Search (CS) algorithm has been devised by using chaotic sequence, population diversity information etc to solve those formulated optimization problems. A new Co-occurrence matrix's features based objective function is also devised to preserve the original brightness. Peak-signal to noise ratio (PSNR) acts as objective function to find optimal range of enhanced images. Experimental results prove the supremacy of the proposed CS over traditional CS algorithm.

Color-Space-Based Visual-MIMO for V2X Communication.

In this paper, we analyze the applicability of color-space-based, color-independent visual-MIMO for V2X. We aim to achieve a visual-MIMO scheme that can maintain the original color and brightness while performing seamless communication. We consider two scenarios of GCM based visual-MIMO for V2X. One is a multipath transmission using visual-MIMO networking and the other is multi-node V2X communication. In the scenario of multipath transmission, we analyze the channel capacity numerically and we illustrate the significance of networking information such as distance, reference color (symbol), and multiplexing-diversity mode transitions. In addition, in the V2X scenario of multiple access, we may achieve the simultaneous multiple access communication without node interferences by dividing the communication area using image processing. Finally, through numerical simulation, we show the superior SER performance of the visual-MIMO scheme compared with LED-PD communication and show the numerical result of the GCM based visual-MIMO channel capacity versus distance.

Reattachment of an Incompletely Fractured Anterior Tooth by a Conservative Approach

The major objectives of restoration dentistry are to restore teeth in a way that allies conservation of healthy dental tissue, esthetics, function, and durability. The ideal would be to attain restorations that are as strong as the natural teeth, which seems unnoticeable even to dentists and more demanding patients.3 Thus, in many clinical situations, the best option for fractured anterior teeth is reattachment of the tooth fragment because of the following reasons: • It reinstates the natural shape, contour, surface texture, and occlusal alignment. • Original color and brightness of the tooth are maintained. • Incisal edge of the tooth fragment wears at a similar rate to the adjacent teeth, whereas a composite restoration will likely wear more rapidly. • Less chair-side time is required so the reattachment is much more economical. Attachment of a tooth fragment can be achieved with good esthetic and functional results, even in more complex situations where pulp and/or the biologic width are involved.4-10 With the evolution of adhesive systems, offering excellent bonding to dentin,11,12 reattachment of dental fragment has been a noninvasive treatment offering good results,4,5,7,13-17 even when performed under challenging conditions.9 Bevels, chamfers, grooves, and undercuts apparently make no difference in the prognosis.9,18

Contrast Image Enhancement Using Multi-Histogram Equalization

Mean separated histogram equalization in order to preserve the original mean brightness has been proposed. To provide the minimum mean brightness error after the histogram modification, the input image's histogram is successively divided by the factor of 2 until the mean brightness error is satisfied the defined threshold. Then each divided group or sub-histogram will be independently equalized based on the proportional input mean. To provide the overall minimum mean brightness error, each group will be controlled by adding some certain pixels from the adjacent grey level of the next group for giving its mean near by the corresponding the divided mean. However, it still exists some little error which will be put into the next adjacent group. By successive dividing the original histogram, we found that the absolute mean brightness error is gradually decreased when the number of group is increased. Therefore, the error threshold is assigned in order to automatically dividing the original histogram for obtaining the desired absolute mean brightness error (AMBE). This process will be applied to the color image by treating each color independently.

Diversity Conserved Chaotic Artificial Bee Colony Algorithm based Brightness Preserved Histogram Equalization and Contrast Stretching Method

This study is organized into two parts. The first part introduces two image enhancement methods with the ability to preserve the original brightness of the image. These two methods are: optimal ranged brightness preserved contrast stretching (ORBPCS) method and weighted thresholded histogram equalization (WTHE) method. The efficiency of these two methods crucially depends on the method's associated parameters. To find the optimal values of the parameters Artificial Bee Colony (ABC) algorithm and a novel objective function have been employed in this study. The second part of this study mainly concentrates on the efficiency increment of ABC algorithm and to develop the proper objective functions to preserve the original brightness of the image. Some new mechanisms like population diversity measurement technique, use of chaotic sequence etc. are also introduced to enhance the efficiency of traditional ABC algorithm. The objective functions have been developed by using co-occurrence matrix and peak-signal to noise ratio (PSNR).

Wavelength-adaptive dehazing using histogram merging-based classification for UAV images.

Since incoming light to an unmanned aerial vehicle (UAV) platform can be scattered by haze and dust in the atmosphere, the acquired image loses the original color and brightness of the subject. Enhancement of hazy images is an important task in improving the visibility of various UAV images. This paper presents a spatially-adaptive dehazing algorithm that merges color histograms with consideration of the wavelength-dependent atmospheric turbidity. Based on the wavelength-adaptive hazy image acquisition model, the proposed dehazing algorithm consists of three steps: (i) image segmentation based on geometric classes; (ii) generation of the context-adaptive transmission map; and (iii) intensity transformation for enhancing a hazy UAV image. The major contribution of the research is a novel hazy UAV image degradation model by considering the wavelength of light sources. In addition, the proposed transmission map provides a theoretical basis to differentiate visually important regions from others based on the turbidity and merged classification results.

LOFAR sparse image reconstruction

Context. The LOw Frequency ARray (LOFAR) radio telescope is a giant digital phased array interferometer with multiple antennas distributed in Europe. It provides discrete sets of Fourier components of the sky brightness. Recovering the original brightness distribution with aperture synthesis forms an inverse problem that can be solved by various deconvolution and minimization methods Aims. Recent papers have established a clear link between the discrete nature of radio interferometry measurement and the "compressed sensing" (CS) theory, which supports sparse reconstruction methods to form an image from the measured visibilities. Empowered by proximal theory, CS offers a sound framework for efficient global minimization and sparse data representation using fast algorithms. Combined with instrumental direction-dependent effects (DDE) in the scope of a real instrument, we developed and validated a new method based on this framework Methods. We implemented a sparse reconstruction method in the standard LOFAR imaging tool and compared the photometric and resolution performance of this new imager with that of CLEAN-based methods (CLEAN and MS-CLEAN) with simulated and real LOFAR data Results. We show that i) sparse reconstruction performs as well as CLEAN in recovering the flux of point sources; ii) performs much better on extended objects (the root mean square error is reduced by a factor of up to 10); and iii) provides a solution with an effective angular resolution 2-3 times better than the CLEAN images. Conclusions. Sparse recovery gives a correct photometry on high dynamic and wide-field images and improved realistic structures of extended sources (of simulated and real LOFAR datasets). This sparse reconstruction method is compatible with modern interferometric imagers that handle DDE corrections (A- and W-projections) required for current and future instruments such as LOFAR and SKA

Contrast enhancement using real coded genetic algorithm based modified histogram equalization for gray scale images

ABSTRACTHistogram equalization is a well‐known technique used for contrast enhancement. The global HE usually results in excessive contrast enhancement because of lack of control on the level of contrast enhancement. A new technique named modified histogram equalization using real coded genetic algorithm (MHERCGA) is aimed to sweep over this drawback. The primary aim of this paper is to obtain an enhanced method which keeps the original brightness. This method incorporates a provision to have a control over the level of contrast enhancement and applicable for all types of image including low contrast MRI brain images. The basic idea of this technique is to partition the input image histogram into two subhistograms based on a threshold which is obtained using Otsu's optimality principle. Then, bicriteria optimization problem is formulated to satisfy the aforementioned requirements. The subhistograms are modified by selecting optimal contrast enhancement parameters. Finally, the union of the modified subhistograms produce a contrast enhanced and details preserved output image. While developing an optimization problem, real coded genetic algorithm is applied to determine the optimal value of contrast enhancement parameters. This mechanism enhances the contrast of the input image better than the existing contemporary HE methods. The quality of the enhanced brain image indicates that the image obtained after this method can be useful for efficient detection of brain cancer in further process like segmentation, classification, etc. The performance of the proposed method is well supported by the contrast enhancement quantitative metrics such as discrete entropy and natural image quality evaluator. © 2015 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 25, 24–32, 2015

Contrast Enhancement using Improved Adaptive Gamma Correction with Weighting Distribution Technique

ne of the important techniques in digital image processing is to enhance images. Contrast enhancement is a method that is used to enhance images for viewing process or for further analysis of images. Main idea behind contrast enhancement techniques is to increase contrast and to preserve original brightness of images. In this paper a contrast enhancement technique is proposed that first segments histogram of image recursively and then applies Adaptive Gamma Correction with Weighting Distribution (AGCWD) Technique. The proposed technique is basically an improvement over AGCWD technique and aims to get better contrast enhancement and brightness preservation than AGCWD technique.

Range Limited Quad-Histogram Equalization Method for Image Contrast Enhancement

equalization is a very popular technique for image contrast enhancement. Histogram equalization defines the clarity of picture and sometime improves brightness. But sometime it is not very good for consumer electronics, because of preserving the original brightness. Range limited bi-histogram equalization RLBHE applied for consumer electronics. This paper proposes novel extension of RLBHE referred to as range limited quad- histogram equalization RLQHE. This method is applied as first it divides the input histogram into two sub-images by a threshold. Then again two sub-images divide in to two sub- images by using another threshold that minimizes intra- class variance. All these sub-images separate the object from background. Then, Range means it calculate the minimum absolute mean brightness error between actual image and equalized image. The result shows that proposed method is better than previous method for image contrast enhancement. Proposed method preserves original brightness as actual image. It is very well suited for consumer electronics product.

A Comparative Analysis of Histogram Equalization based Techniques for Contrast Enhancement and Brightness Preserving

Histogram Equalization (HE) is a simple and effective image enhancement technique.But, it tends to change the mean brightness of the image to the middle level of the permitted range, and hence is not a very suitable for consumer product. While preserving the original brightness is essential to avoid annoying artefacts. To preserve brightness and to enhance contrast of images, numerous methods are introduced, but many of them present unwanted artefacts such as intensity saturation, over-enhancement and noise amplification. In the present paper, available histogram equalization based methods are reviewed and compared with image quality measurement (IQM)tools such as Absolute Mean Brightness Error (AMBE) to assess brightness preserving and Peak Signal-to-Noise Ratio (PSNR) to evaluate contrast enhancement.

Comparison Between GOES-East and -West for Land Surface Temperature Retrieval From a Dual-Window Algorithm

In this letter, land surface temperature (LST) is derived from Geostationary Operational Environmental Satellite (GOES)-East (GOES-E) and GOES-West (GOES-W) using a revised dual-window LST algorithm developed by Sun and Pinker in 2004. LST derived from GOES is also evaluated against ground observations. The results show that the LSTs from GOES-E are warmer than those from GOES-W in the morning but lower in the afternoon, while there is no big difference around noon and during night. It is found that the original brightness temperatures from GOES-E and GOES-W show similar patterns to LSTs over time. The discrepancy in LSTs is most probably due to the fact that the Earth surface is warmer in GOES-E than in GOES-W in the morning but cooler in the afternoon. Some other factors may include the difference in satellite viewing geometry, image navigation and registration, calibration, and spectral response functions. It is expected that these effects should be small as those demonstrated in nighttime difference. When evaluated against the ground observations, over the overlap region, the LST bias error is positive from GOES-E but negative from GOES-W in the morning, leading to a positive LST difference, while the bias from GOES-W is close to zero but negative from GOES-E in the afternoon, resulting in a negative LST difference. Nevertheless, the LST root-mean-square errors from GOES-E and GOES-W are very close and reach the maximum around noontime. To synergistically use LST from different satellite sensors, we suggest using nighttime data; further study is needed to best use daytime LSTs.

Study of Various Histogram Equalization Techniques

Histogram equalization (HE) works well on single channel images for contrast enhancement. However, the technique used is ineffective on multiple channel images. So, it is not suitable for consumer electronic products, where preserving the original brightness is necessary in order not to introduce unnecessary visual deterioration. Bi-histogram equalization (BHE) has been developed and it is analyzed mathematically.BHE separates the input image's histogram into two, based on its mean before equalizing them independently so that it can preserve the original brightness up to certain extends. Recursive Mean-Separate Histogram Equalization (RMSHE) is another technique to provide better and scalable brightness preservation for gray scale and color images. While the separation is done only once in BHE, RMSHE performs the separation recursively based on their respective mean. It is analyzed mathematically that the output images mean brightness will converge to the input images mean brightness as the number of recursive mean separation increases. The recursive nature of RMSHE also allows scalable brightness preservation, which is very useful in consumer electronics. Finally a comparative study was made to analyze all the above methods using gray scale and color images.

Ultrasound Tissue Characterization of the Normal Kidney

Ultrasound tissue characterization (USTC) is a precursor of ultrasound virtual histology (USVH), already applied to B-mode images of coronary, carotid, and peripheral arteries, as well as venous thrombosis. Elevated echogenicity has been described for a rejected transplanted kidney. We analyzed data from healthy young adults as reference for further renal USTC. Ultrasound kidney images of 10 volunteers were analyzed. Pixel brightness in the 0-to-255 range was rescaled to zero for black and 200 for fascia brightness before automatic classification into 14 ranges, including "blood-like" (0-4), "fat-like" (8-26), "hypoechoic muscle-like" (41-60), "hyperechoic muscle-like" (61-76), 4 ranges of "fiber-like" (112-196), "calcium-like" (211-255) and intermediary intervals. Nomenclature was readapted using nonechoic, hypoechoic I to IV, echoic I to IV, hyperechoic I to IV, and saturated echoes to avoid inference to actual kidney tissue. Descriptive and comparative statistics were based on percentages of pixels in specific brightness ranges. Eight women and 2 men, 26 ± 4 years (range, 22-34 years) old, were studied. Kidney length was 10.5 ± 0.9 cm (9.0-12.0 cm). Doppler US resistivity index was 0.67 ± 0.03 (0.62-0.71). Original fascia brightness converted to 200 value had a mean ± SD of 206 ± 16 (range, 181-236). Kidney grayscale median averaged 37 ± 6 (27-48). Most pixels were hypoechoic II to IV (8-60), averaging 78% ± 6% (66%-87%). Percentages for fat-like, intermediary fat/muscle-like, and hypoechoic muscle-like intervals averaged 25%, 28%, and 25%, respectively. A reference database for USTC/USVH of normal young kidneys was created for future comparisons with transplanted and abnormal kidneys. Normal renal echoes have low brightness. Hyperechoic pixels may represent abnormalities.

Range Limited Bi-Histogram Equalization for image contrast enhancement

Histogram equalization is a popular technique for enhancing image contrast. However, it tends to change the brightness of an image and hence, this technique is not very well suited to be implemented in consumer electronics, where preserving the original brightness is essential to avoid annoying artifacts. This paper proposes a novel extension of bi-histogram equalization referred to as Range Limited Bi-Histogram Equalization (RLBHE). First, RLBHE divides the input histogram into two independent sub-histograms by a threshold that minimizes the intra-class variance. This is done in order to effectively separate the objects from the background. Then, range of the equalized image is calculated to yield minimum absolute mean brightness error between the original image and the equalized one. The experimental results show that the proposed method has better performance than the existing methods, and preserve the original brightness quite well, so that it is possible to be utilized in consumer electronic products.

MRT letter: Extended depth from focus reconstruction method for stretch zone measurement in 15‐5PH steel

The stretch zone width (SZW) data for 15-5PH steel CTOD specimens fractured at -150°C to + 23°C temperature were measured based on focused images and 3D maps obtained by extended depth-of-field reconstruction from light microscopy (LM) image stacks. This LM-based method, with a larger lateral resolution, seems to be as effective for quantitative analysis of SZW as scanning electron microscopy (SEM) or confocal scanning laser microscopy (CSLM), permitting to clearly identify stretch zone boundaries. Despite the worst sharpness of focused images, a robust linear correlation was established to fracture toughness (K(C) ) and SZW data for the 15-5PH steel tested specimens, measured at their center region. The method is an alternative to evaluate the boundaries of stretched zones, at a lower cost of implementation and training, since topographic data from elevation maps can be associated with reconstructed image, which summarizes the original contrast and brightness information. Finally, the extended depth-of-field method is presented here as a valuable tool for failure analysis, as a cheaper alternative to investigate rough surfaces or fracture, compared to scanning electron or confocal light microscopes.

Eliminating the influence of attitude on brightness temperatures measurement for polarimetric microwave radiometer

In order to meet the requirement of accurate detection for polarimetric microwave radiometer, in this paper, we study on the influence of attitude on brightness temperatures received by the radiometer. Correction for brightness temperatures errors is also analyzed. The relationship between the misspecification of the attitude and the incidence angle together with polarization rotation angle is established. The variation of brightness temperatures with the change of incidence angle and polarization rotation angle is simulated. We simulate the original observational brightness temperatures of the radiometer. A method based on the radiative transfer model for compensating attitude offset to correct brightness temperatures errors is presented. Taking vertical brightness temperature and the third Stokes parameter brightness temperature for example, our method can eliminate the influence of attitude offset on the observation of brightness temperatures effectively, the result can satisfy the accuracy requirement of data preprocessing for polarimetric microwave radiometer.

Scotopic Foveal Afterimages

If, after being in the dark for many minutes, one views an extended surface under dim (scotopic) illumination, one fails to see any hint of the dark spot at the center of gaze that might be expected from the absence of rods in the fovea. Here we report that, if the surface is suddenly completely darkened, one sees for a few seconds a relatively bright spot, about 2 deg in size, at the point of fixation. If the surface is now restored to its original brightness, a dark spot of similar size appears where one fixates, that again lasts for several seconds. All this can be observed with no elaborate apparatus.