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Objective Quality Assessment of Image Enhancement Methods in Digital Mammography - A Comparative Study
摘要： Mammography is the primary and most reliable technique for detection of breast cancer. Mammograms are examined for the presence of malignant masses and indirect signs of malignancy such as micro calcifications, architectural distortion and bilateral asymmetry. However, Mammograms are X-ray images taken with low radiation dosage which results in low contrast, noisy images. Also, malignancies in dense breast are difficult to detect due to opaque uniform background in mammograms. Hence, techniques for improving visual screening of mammograms are essential. Image enhancement techniques are used to improve the visual quality of the images. This paper presents the comparative study of different pre-processing techniques used for enhancement of mammograms in mini-MIAS data base. Performance of the image enhancement techniques is evaluated using objective image quality assessment techniques. They include simple statistical error metrics like PSNR and human visual system (HVS) feature based metrics such as SSIM, NCC, UIQI, and Discrete Entropy
关键词： Adaptive median filter,HE,Contrast stretching,Wavelet transforms,CLAHE
更新于2025-09-23 15:23:52
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[Communications in Computer and Information Science] Advances in Computing and Data Sciences Volume 905 (Second International Conference, ICACDS 2018, Dehradun, India, April 20-21, 2018, Revised Selected Papers, Part I) || Two Stage Histogram Enhancement Schemes to Improve Visual Quality of Fundus Images
摘要： A fundus image plays a signi?cant role to analyze a wide variety of ophthalmic conditions. One of the major challenges faced by ophthalmologist in the analysis of fundus images is its low contrast nature. In this paper, two stage histogram enhancement schemes to improve the visual quality of fundus images are proposed. Fuzzy logic and Histogram Based Enhancement algorithm (FHBE) and Contrast Limited Adaptive Histogram Equalization (CLAHE) algorithm are cascaded one after the other to accomplish the two stage enhancement task. This results in two new enhancement schemes, namely FHBE-CLAHE and CLAHE-FHBE. The analysis of the results based on its visual quality shows that two stage enhancement schemes outperforms individual enhancement schemes.
关键词： Fundus images,FHBE,CLAHE,Image enhancement
更新于2025-09-23 15:23:52
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Comparative study of image enhancement techniques using histogram equalization on degraded images
摘要： Image Enhancement technique plays a vital role in digital image processing for making an image to be useful for various applications. This technique is used to improve the quality of degraded images. Usually, the degradation is not evenly spread throughout the image, but most of the time it varies from region to region. Our aim is to first identify the region where enhancement is required and improve that region without disturbing its neighbourhood which does not require any improvement.
关键词： Image Histogram,Contrast Limited Adaptive Histogram Equalization (CLAHE),Image Enhancement,Histogram Equalization (HE)
更新于2025-09-09 09:28:46
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Guidelines for Underwater Image Enhancement Based on Benchmarking of Different Methods
摘要： Images obtained in an underwater environment are often affected by colour casting and suffer from poor visibility and lack of contrast. In the literature, there are many enhancement algorithms that improve different aspects of the underwater imagery. Each paper, when presenting a new algorithm or method, usually compares the proposed technique with some alternatives present in the current state of the art. There are no studies on the reliability of benchmarking methods, as the comparisons are based on various subjective and objective metrics. This paper would pave the way towards the definition of an effective methodology for the performance evaluation of the underwater image enhancement techniques. Moreover, this work could orientate the underwater community towards choosing which method can lead to the best results for a given task in different underwater conditions. In particular, we selected five well-known methods from the state of the art and used them to enhance a dataset of images produced in various underwater sites with different conditions of depth, turbidity, and lighting. These enhanced images were evaluated by means of three different approaches: objective metrics often adopted in the related literature, a panel of experts in the underwater field, and an evaluation based on the results of 3D reconstructions.
关键词： automatic colour equalization,3D reconstruction,non-local dehazing,benchmark,lab,colour correction,screened poisson equation,CLAHE,underwater image enhancement,dehazing
更新于2025-09-09 09:28:46
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An Illumination Invariant Face Recognition Using 2D Discrete Cosine Transform and Clahe
摘要： Automatic face recognition performance is affected due to the head rotations and tilt, lighting intensity and angle, facial expressions, aging and partial occlusion of face using Hats, scarves, glasses etc.In this paper, illumination normalization of face images is done by combining 2D Discrete Cosine Transform and Contrast Limited Adaptive Histogram Equalization. The proposed method selects certain percentage of DCT coefficients and rest is set to 0. Then, inverse DCT is applied which is followed by logarithm transform and CLAHE. Thesesteps create illumination invariant face image, termed as ‘DCT CLAHE’ image. The fisher face subspace method extracts features from ‘DCT CLAHE’ imageand features are matched with cosine similarity. The proposed method is tested in AR database and performance measures like recognition rate, Verification rate at 1% FAR and Equal Error Rate are computed. The experimental results shows high recognition rate in AR database.
关键词： CLAHE,recognition rate,2D DCT,Facerecognition,AR,DCT CLAHE
更新于2025-09-04 15:30:14