In this paper, a powerful contrast enhancement algorithm based on the histogram equalization, called triple dynamic clipped histogram equalization (TDCHE) is introduced. The proposed method consists of four main processes including partitioning, clipping, mapping and equalization. At first, the input image histogram is partitioned into three portions with a same number of pixels. Next, the histogram clipping process is performed by comparing the clipped threshold level with the average intensities occurred on each sub-histogram. Then, each sub-histogram is mapped to a new dynamic range using simple calculations and finally, equalization process of each histogram is independently accomplished. The proposed TDCHE technique is presented to achieve multiple objectives of maximum average information content (entropy), enhancement ratio control and maintaining the reasonable brightness. In addition, this method leads to a natural enhancement in the output image by providing sharp images, while preserving maximum details far from unnatural phenomena such as intensity saturation and noise enhancement. Evaluation of the proposed TDCHE method performance in terms of information content as well as visual quality shows perceived superiority of the proposed algorithm in comparison to the previously presented methods based on histogram equalization.

Most intelligent underwater vehicles and remote control marine vehicles are usually equipped with optical cameras for underwater photography. However, due to water properties and its impurity, the quality of the images taken by these imaging equipment is not desirable, enough. Because, water reduces the light and by increasing the deep of water, the further light will diminish, which will result in the absorption of colors by water. Hence, image processing operations are crucial for underwater images .In this paper, a new method has been proposed to improve the contrast and quality of underwater images. In the proposed method, the two methods of contrast stretching and histogram equalization have been employed. In the histogram equalization phase, new methods have been introduced for thresholding and histogram clipping. The proposed method has been applied on a benchmark images dataset and the results have been compared with the results of common methods. The analysis of the proposed method results, compared to the Sathya et al., which is the best method compares to other rival methods, shows 40.16% increase in the contrast of the images, in the best case

Improved image contrast is one of the most important operations used in image processing and visual processing applications. Histogram equalization is one of the most powerful ways to increase the contrast and improve the quality of digital images. However, this method usually causes an excessive increase in contrast and a loss of part of the image details. Many problems have been resolved in the past two decades in order to overcome the many problems of histogram equalization. In this paper, we have reviewed, categorized and compared the methods proposed in the field of histogram equalization for twenty years.

The equalization of histograms is a simple and efficient process for contrast enhancement. This paper presents equalization of the bi-histogram with the level of the entropy-based plateau. In the first step, the input histogram is divided into two separate sub-histograms, using the mean brightness as a primary threshold of total image pixels. The mentioned threshold is updated in a way that it minimizes the different values of discrete entropy between each section. Then, based on the measured plateau value, these sub-histograms are clipped to prevent unnecessary enhancement. Finally, the image intensity is stretched based on the cumulative distribution function. Laboratory results show that this method gives better outcomes of enhancement, especially in the presence of noise, compared to some two-section methods of preserving of brightness of the histogram equalization.

The objective of this study was to determine the chronology of changes in blood pressure in renal hypertension induced by solid plexiglass clips in rats. Saw blades with the thickness of 0.21-0.22 mm were used to make clips sized 4 × 2 × 2 mm from a piece of 2-mm thick plexiglass. Rats were subjected to sham-operation or left renal arterial clipping, and 1, 2, 3 and 4 weeks later blood pressure, and heart and kidneys weights were determined. Relative to those of sham-operated rats, mean blood pressure of left renal artery-clipped rats were significantly higher at week 1 through 4 after clipping. Left renal artery clipping was also associated with significant increases in heart and right kidney weights and significant decrease in left kidney weight. The findings suggest that clipping of left renal artery using solid plexiglass clips resulted in changes in blood pressure, heart and left and right kidneys weights similar to reported changes in hypertension induced by silver clips.

There are several methods for the ligation of structures during minimally invasive operations. The hem-o-lok clip is a nonabsorbable polymer clip with a lock engagement feature. There are few reports about its use in minimally invasive general surgical procedures. In this report, we describe our experience with the hem-o-lok clip during basic, minimally invasive, general surgery procedures and the adverse events during application of the hem-o-lok.Patients and We retrospectively reviewed all laparoscopic appendectomies (LAs), cholecystectomies (LCs), and splenectomies (LSs), performed by 6 general surgeons at a university-affiliated hospital over 4 years. Clip failure was defined as intraoperative or postoperative bleeding due to clip malfunction that necessitated placement of another clip, conversion to an open procedure, or postoperative re-exploration. Leakage from the cystic duct and appendiceal stump was also considered clip failure. A search of the US Food and Drug Administration Manufacturer and User Facility Device Experience (MAUDE) database using the appropriate keywords was performed on July 7, 2011. This online resource contains reports of adverse events involving medical devices. Over a 4-year period, 856 laparoscopic operations, comprising 770 LC, 55 LS, and 31 LA, were performed. We did not observe any incidence of clip failure. There were 22 reports of hem-o-lok clip failure in the MAUDA database. Eighty-two percent (n = 18) of clip failures were reported during laparoscopic nephrectomy. There was no report of failure after LA. There were 2 reported clip failures after LC (with bile leakage) and 1 after LS (tearing of splenic vessels with intraoperative bleeding). There was also a report of migration of the hem-o-lok clip into the common bile duct, which occurred 4 years after a complicated LC. Hem-o-lok clips that are properly applied during basic laparoscopic procedures are a secure option for the ligation of the structures. Surgeons must be educated regarding the proper application technique.

Histogram Equalization technique is one of the basic methods in image contrast enhancement. Using this method, in the case of images with uniform gray levels (with narrow histogram), causes loss of image detail and the natural look of the image. To overcome this problem and to have a better image contrast enhancement, a new two-step method was proposed. In the first step, the image histogram is partitioned into some sub-histograms according to mean value and standard deviation, which will be controlled with PSNR measure. In the second step, each sub-histogram will be improved separately and locally with traditional histogram equalization. Finally, all sub-histograms will be combined to obtain the enhanced image. Experimental results shows that this method would not only keep the visual details of the histogram, but also enhance image contrast.

For assessing clipping (simulated grazing) effects on Stipa barbata as an important species, a half hectare exclosure field was established before 2007 growing season in Majidabad paddock. Inside the exclosure area, 40 plants were selected of which 10 replications were allocated to each specific treatment of ocular-estimated hand clipping of 25, 50 and 75 percent of annual growth. Ten replications were assigned as control (unclipped) plants. Clippings were done monthly during the three months of current grazing season. Monthly-clipped plant materials were dried in free air to calculate the accurate clipping intensity. In addition, the residues of all plants (also controls) were clipped and dried simultaneously at the end of growth season. The study was done for four years. A split plot in time was used as the statistical design and analysis. The results showed that the main effect of year and different clipping intensities and interactions effect of different clipping intensity and years were significant on forage production but no significant difference was found on final height and number of reproductive branches. Most and least amount of production were related to the years of 2007 and 2008 with 508 and 167 mm of rainfall, respectively and 75% treatment (severe clipping). As the overall conclusion, regarding the environmental and management variations of this species, it is adapted with light clipping (25%) and maximum allowable use of one third of the annual yield growth.

In this paper, a method is proposed to automatically select reference image in histogram matching. Histogram matching is one of the simplest spatial image enhancement methods which improves contrast of the initial image based on histogram of the reference image. In the conventional histogram matching methods, user should perform several experiments on various images to find a suitable reference image. This paper presents a new method to automatically select the reference image. In this method, images are converted from RGB to HSV, and the illumination (V) components are considered to select the reference image. The appropriate reference image is selected using a similarity measure via measuring the similarity between the histograms of the initial image and histograms of the images in the data base. Indeed, an image with similar histogram to the histogram of the original images is more appropriate to choose as the reference image for histogram matching. Results in this research indicate superiority of the proposed approach, compared to other existing approaches, in image enhancement via histogram matching. In addition, the user would have no concern in selecting an appropriate reference image for histogram matching in the proposed approach. This approach is applicable to both RGB and gray scale images.

This study aimed to evaluate effects of clipping on some growth characteristics of Panicum antidotale. A completely randomized design with 4 treatments including once a week (frequent), every two weeks (moderate), every four weeks (low) and control (unclipped) was carried out in 11 replicates. Shoots were clipped at a height of 7 cm in all treatments. The result showed no significant effects of clipping treatments on total biomass, above-ground and below ground biomass and also number of shoots and roots. Therefore, this species can be considered as tolerant to clipping.