Speeded up robust features for efficient iris recognition

This paper presents a comparative analysis of fundus image enhancement techniques to detect diabetic retinopathy (DR). Medical images frequently suffers from non-uniform illumination, poor contrast and noise, thus these images have to go through pre-processing stage. For image enhancement many techniques are proposed based on spatial domain (histogram). However, these methods usually decline to produce suitable consequences for non-uniform illumination and wide-ranging of low-contract. The comparative analysis and performance evaluation of various enhancement techniques will help in choosing most suitable technique which may significantly improve the detection of diabetic retinopathy. In this paper histogram equalization (HE), adaptive histogram equalization (ADHE), contrast limited adaptive histogram equalization (CLAHE) and exposure based sub-image histogram equalization (ESIHE) techniques are compared for pre-processing of fundus image for detecting DR. For fair analysis of these techniques, histogram, SNR, entropy, absolute mean brightness error and peak signal-to-noise ratio (PSNR) of fundus images are analyzed by using MATLAB.

Adaptive histogram equalization (AHE) is a method for adaptive contrast enhancement of digital images. It is an automatic, reproducible method for the simultaneous viewing of contrast within a digital image with a large dynamic range. Recent experiments have shown that in specific cases, there is no significant difference in the ability of AHE and linear intensity windowing to display gray-scale contrast. More recently, a variant of AHE which limits the allowed contrast enhancement of the image has been proposed. This contrast-limited adaptive histogram equalization (CLAHE) produces images in which the noise content of an image is not excessively enhanced, but in which sufficient contrast is provided for the visualization of structures within the image. Images processed with CLAHE have a more natural appearance and facilitate the comparison of different areas of an image. However, the reduced contrast enhancement of CLAHE may hinder the ability of an observer to detect the presence of some significant gray-scale contrast. In this report, a psychophysical observer experiment was performed to determine if there is a significant difference in the ability of AHE and CLAHE to depict gray-scale contrast. Observers were presented with computed tomography (CT) images of the chest processed with AHE and CLAHE. Subtle artificial lesions were introduced into some images. The observers were asked to rate their confidence regarding the presence of the lesions; this rating-scale data was analyzed using receiver operating characteristic (ROC) curve techniques. These ROC curves were compared for significant differences in the observers' performances. In this report, no difference was found in the abilities of AHE and CLAHE to depict contrast information.

A contrast enhancement method for improving the segmentation of breast lesions on ultrasonography

The identification of COVID-19 using chest X-ray (CXR) images plays a critical role in managing the pandemic by providing a rapid, non-invasive, and accessible diagnostic tool. This study evaluates the impact of different image preprocessing techniques on the performance of deep learning models for COVID-19 classification based on COVID-19 Radiography Database, which includes 10,192 normal CXR images, 6012 lung opacity (non-COVID lung infection) images, and 1345 viral pneumonia images. Along with the images, corresponding lung masks are also included to aid in the segmentation and analysis of lung regions. Specifically, three convolutional neural network (CNN) models were developed, each using a distinct preprocessing method: Contrast Limited Adaptive Histogram Equalization (CLAHE), traditional histogram equalization, and no preprocessing. The results revealed that while the CLAHE-enhanced model achieved the highest training accuracy (93.26%) and demonstrated superior stability during training, it showed lower performance in the validation phase, with validation accuracy of 91.31%. In contrast, the model with no preprocessing, which exhibited slightly lower training accuracy (92.98%), outperformed the CLAHE model during validation, achieving the highest validation accuracy of 91.50% and the lowest validation loss. The histogram equalization model demonstrated performance similar to that of CLAHE but with slightly higher validation loss and accuracy compared to the unprocessed model. These findings suggest that while CLAHE excels in enhancing image details during training, it may lead to overfitting and reduced generalization ability. In contrast, the model without preprocessing showed the best generalization and stability, indicating that preprocessing techniques should be chosen carefully to balance feature enhancement with the need for generalization in real-world applications. This study underscores the importance of selecting appropriate image preprocessing techniques to enhance deep learning models' performance in medical image classification, particularly for COVID-19 detection. Histogram Equalization The results contribute to ongoing efforts to optimize diagnostic tools using AI and image processing.

Mammography is a technique which uses X-rays to take mammographic images of the breast, but identifying abnormalities from a mammogram is a challenging task. Many Computer-Aided Diagnosis (CAD) systems are developed to aid the classification of mammograms, as they search in digitized mammographic images for any abnormalities like masses, microcalcification which is difficult to identify especially in dense breasts. The first step in designing a CAD system is preprocessing. It is the process of improving the quality of the image. This paper focuses on the techniques involved in preprocessing the mammogram images to improve its quality for early diagnosis. Preprocessing involves filtering the image, applying image enhancement techniques like Histogram Equalization (HE), Adaptive Histogram Equalization (AHE), Contrast-Limited Adaptive Histogram Equalization (CLAHE), Contrast Stretching, and Bit-plane slicing; filtering techniques like mean, median, Gaussian and Wiener filters are also applied to the mammogram images. The performance of these image enhancement techniques are evaluated using quality metrics, namely Mean Square Error (MSE), Peak Signal-to-Noise Ratio (PSNR), and Contrast-to-Noise Ratio.

In this paper we present a generalized algorithm for unsharp masking of medical images which takes as one of its inputs a high contrast image underwent local adaptive contrast enhancement. Selection of optimal values of the number of histogram bins, processing window size and intensity lower and upper limits in iterative manner is part of applying Contrast Limited Adaptive Histogram Equalization (CLAHE). Experimental results reveal higher quality of the output images both in terms of root mean square contrast and sharpness. Achieved quality, both visually and quantitatively, is compared to that from the Adaptive Histogram Equalization (AHE) algorithm, limited histogram stretching and ordinary histogram equalization which proves its applicability. The algorithm is considered appropriate for processing a number of types of images, such as CT, X-ray, etc.

With the advancement of technology and its implementation in the medical field, a lot of new methods and techniques are created to solve complex real-life problems. Breast cancer is a major issue in women and corresponds to a quarter of deaths related to it. In this paper, we have used the MIAS dataset which consists of 322 mammograms (161 pairs). Mammograms are cheap and easy to understand. For contrast enhancement, we have used contrast limited adaptive histogram equalization (CLAHE) with a clip size of 0.2. We have compared the PSNR of histogram equalization (HE), CLAHE, minimum mean brightness error bi-histogram equalization (MMBEBHE), and recursive mean-separate histogram equalization (RMSHE). We found that CLAHE and RMSHE perform better than MMBHBHE and HE. A convolutional neural network (CNN) architecture is created for feature extraction, and a total of 2115 features is provided for classification. SVM, decision tree, and random forest are used as classifiers. The accuracy achieved by SVM, decision tree, and random forest is 92.30, 94.03, and 95.05%, while using decision fusion (SVM, decision tree, and random forest), the highest accuracy of 96.12% is achieved.KeywordsBreast cancerCLAHEImage fusionMachine learning

In the field of image processing, improving low-contrast images is essential for enhancing the visibility of features that may be hard to see due to slight intensity variations. This issue often arises with images captured in poor lighting or unfavorable conditions, which can impede tasks such as feature extraction, object recognition, and edge detection. This paper presents an algorithm that employs fuzzy techniques to enhance low-contrast images. The approach utilizes a Pythagorean fuzzy set, which is an advanced version of a fuzzy set. The Pythagorean fuzzy set, by integrating membership and non−membership degrees, offers a more precise representation of image uncertainty. The proposed method constructs an increasing function to calculate the degree of non−membership, thereby amplifying the effectiveness of the enhanced image. By integrating this method with contrast limited adaptive histogram equalization, alongside a color restoration technique and brightness-preserving dynamic histogram equalization, the brightness and natural appearance of the original low-contrast image are maintained. We compare our approach to other methods, including conventional histogram equalization, intuitionistic fuzzy generators, interval−valued intuitionistic fuzzy generators, interval−valued intuitionistic fuzzy with contrast limited adaptive histogram equalization, LightNet, and FlightNet. Experimental results indicate that our method surpasses the techniques currently utilized in terms of visibility and color accuracy. Performance evaluation is performed using metrics such as the absolute mean brightness error, contrast improvement index, and structural similarity index.

Chest radiography is a common diagnostic imaging test, which contains an enormous amount of information about a patient. However, its interpretation is highly challenging. The accuracy of the diagnostic process is greatly influenced by image processing algorithms; hence enhancement of the images is indispensable in order to improve visibility of the details. This paper aims at improving radiograph parameters such as contrast, sharpness, noise level, and brightness to enhance chest radiographs, making use of a triangulation method. Here, contrast limited adaptive histogram equalization technique and noise suppression are simultaneously performed in wavelet domain in a new scheme, followed by morphological top-hat and bottom-hat filtering. A unique implementation of morphological filters allows for adjustment of the image brightness and significant enhancement of the contrast. The proposed method is tested on chest radiographs from Japanese Society of Radiological Technology database. The results are compared with conventional enhancement techniques such as histogram equalization, contrast limited adaptive histogram equalization, Retinex, and some recently proposed methods to show its strengths. The experimental results reveal that the proposed method can remarkably improve the image contrast while keeping the sensitive chest tissue information so that radiologists might have a more precise interpretation.

A new technique for image contrast enhancement is proposed in this paper. The technique is based on the variational mode decomposition (VMD) of image and various histogram equalization approaches. The original image is decomposed into different sub-images or modes using VMD. The histogram equalization approaches such as the conventional histogram equalization, the contrast limited adaptive histogram equalization are applied to the mode1 of the original image. For obtaining the enhanced image, a weighting scheme is introduced to combine the processed mode1 image and the original image. The proposed technique is evaluated using various images including the medical image. The experimental results demonstrate that the proposed technique outperforms the existing methods for image enhancement. For medical images, the PSNR and the image quality index values improve by using the proposed technique over various HE approaches.

Image upgrade is essential for giving improved data to other image handling methods. Also, the requirement for differentiation improvement to all-encompassing image is a usually performed examination by dental specialists and oral specialists in regular practice and is a critical indicative apparatus. It covers a more extensive zone than a traditional intraoral x-beam and, subsequently, gives important data about the maxillary sinuses, tooth situating and other bone variations from the norm. Thusly, it is anything but difficult to distinguish and perceive valuable data. In this pursuit was utilized the calculation of Principle Component Analysis (PCA) to upgrade the subtle elements of images and enhance the quality the image, by its joining with strategy for difference improvement, and highlights extraction that take from the upgrade technique to limit mistakes in images, along these lines enhance the execution of the framework, image upgrade strategies used to deliver more reasonable images for identification and extraction. Three principle computerized image process strategies: Contrast Stretching, Histogram Equalization and, Contrast Limited Adaptive Histogram Equalization , were considered to build the improvement image, and evacuate clamor, separately however low quality and the image is light angle in hues and less clear . In this exploration we will, pre-prepared images were assessed utilizing current image recognition and highlight extraction techniques Speeded Up Robust Features (SURF) calculations after go in improvement strategies. After that PCA embed the yield vector from SURF. Gotten results demonstrated that upgrade image expanded after number of separated highlights and diminished mistakes amid info image in PCA. Therefore, the impacts of various pre-process procedures were thought about in the paper and the assessment parameters are figured which demonstrate that proposed work gives better execution from the image broke down under PSNR to enhance the dependability of proposed strategy from the outcomes.

Road crack detection is a crucial safety measure for any country, especially in regions with complex road networks. In India, most roads are well-connected to cities and urban areas. However, urban roads often suffer frequent damage due to various factors. This study focuses on detecting road damage in Indian urban areas using a Deep Convolutional Neural Network (DCNN). We have developed a model specifically designed for identifying cracks in Indian urban roads. To evaluate the proposed model, we collected over 700 images of damaged roads from different urban locations across Tamil Nadu. In this work, we employed the DCNN algorithm for road crack detection, which has proven to be an efficient approach. The proposed method incorporates Histogram Equalization (HE) and Contrast Limited Adaptive Histogram Equalization (CLAHE) to enhance the contrast of road images. This is the first initiative aimed at developing a road damage detection system tailored to urban roadways in India. A comparative analysis was conducted during the preprocessing stage by applying both HE and CLAHE techniques. The model was trained using 5,000 roadside images, including both cracked and non-cracked surfaces. During training, image enhancement was performed using HE and CLAHE, and the processed images were then used to train DCNN. For testing, 700 roadside images (with and without cracks) were utilized, following the same preprocessing steps. The model's accuracy was determined based on its ability to correctly identify road cracks. Results indicate that the proposed model performs effectively for crack detection on CLAHE-enhanced images of Indian urban roads. Additionally, the proposed model's performance was compared with existing models such as ResNet, VGG16, and VGG19 using the same dataset. Evaluation metrics including accuracy, precision, recall, and F1-score were used. The proposed model achieved 98.6% accuracy, 98.5% precision, 99.6% recall, and a 99% F1-score.

Images captured in the sand–dust weather often suffer from serious colour cast and poor contrast, and this has serious implications for outdoor computer vision systems. To address these problems, a normalised gamma transformation‐based contrast‐limited adaptive histogram equalisation (CLAHE) with colour correction in Lab colour space for sand–dust image enhancement is proposed in this study. This method consists of image contrast enhancement and image colour correction. To avoid producing new colour deviation, the input sand–dust images are first transformed from red, green, and blue colour space into Lab colour space. Then, the contrast of the lightness component (L channel) of the sand–dust image is enhanced using CLAHE. To avoid unbalanced contrast, as well as to reduce the overincreased brightness caused by CLAHE, a normalised gamma correction function is introduced to CLAHE. After that, the a and b chromatic components are recovered by a grey‐world‐based colour correction method. Experiments on real sand–dust images demonstrate that the proposed method can obtain the highest percentage of new visible edges for all testing images. The contrast restoration exhibits good colour fidelity and proper brightness.

The retinal blood vessels segmentation algorithm is a powerful tool for the early detection of ophthalmic and cardiovascular diseases and biometrics of the automatic tracking system. Accurate segmentation of blood vessels from a retinal image plays a significant role in the prudent examination of the vessels. Therefore, a combined algorithm of a supervised generalized linear model and an unsupervised contrast limited adaptive histogram equalization is proposed in this paper. Using a generalized linear model integrated with multi-scale information by Gabor wavelet transform, the proposed supervised process can extract more prominent features of retinal blood vessels. Besides, the contrast limited adaptive histogram equalization uses the local histogram equalization, which can handle the illumination variation and adjust the enlargement of details. The method is evaluated on a publicly available DRIVE dataset, as it contains ground truth images precisely marked by experts. The segmentation results show that the proposed method can segment the blood vessels accurately.

Speeded Up Robust Features (SURF) algorithm is a fast robust local feature matching method. Because of the advantage of invariance of scale and rotation, the SURF algorithm has been widely used in the image registration. However, due to the acquired angle, imaging mode, different resolution, SURF algorithm becomes quite difficult in the image registration. This paper presents a normalized SURF algorithm which can reduce the impact of hue difference between remote sensing images. Combined with the idea of two-way matching, the normalized SURF is able to improve the accuracy of the image registration. The experimental results show the normalized SURF algorithm can keep greater accuracy and relatively higher speed of matching than the original SURF algorithm.