Метрики качества медицинских изображений

Проблема определения качества медицинских изображений. Метрики, подходящие для определения качества: меры размытости, сегментации, энтропии изображения, резкости, уровня шумо

A no-reference video quality metric using a natural video statistical model

The demand for high quality multimedia content is increasing rapidly, which has resulted in service providers employing Quality of Service (QoS) strategies to monitor the quality of delivered content. However, the QoS parameters commonly used do not correlate well with the actual quality perceived by the end-users. Numerous objective video quality assessment (VQA) metrics have been proposed to address this problem. However, most of these metrics rely on the availability of additional information from the original undistorted video to perform adequately, which will increase the bandwidth required. This paper presents a No-Reference (NR) VQA algorithm, which extracts a Natural Video Statistical Model using both spatial and temporal features to model the quality experienced by the end-users without needing additional information from the transmitter. These features are based on the observation that the statistics of natural scenes are regular on pristine content but are significantly altered in the presence of distortion. The proposed method achieves a Spearman Rank Order Correlation Coefficient (SROCC) of 0.8161 with subjective data, which is statistically identical and sometimes superior to existing state-of-the-art full and reduced reference VQA metrics.peer-reviewe

System for artefacts monitoring in live video content

Potražnja za videom i aplikacijama kojima je osnova multimedijski sadržaj u velikom je porastu u zadnjih nekoliko godina. Zbog sve veće potražnje za multimedijom pogotovo video multimedijom postoji potreba za pouzdanim alatom s kojim će se procijeniti kvaliteta videa koji se distribuira do krajnjeg korisnika. Iako u znanstvenim krugovima, pitanje analize videa zauzima mnogo pažnje alati za analizu videa su još uvijek vrlo rijetki. U ovom radu predstavljena je aplikacija koja omogućava bez referentnu detekciju video artefakata u stvarnom vremenu i koja je namijenjena za korisnike koji rade na produkciji videa, distribuciji videa, proizvodnjom hardvera, odnosno pripadajućeg softvera i znanstvenim istraživanjima. Aplikacija ima mogućnost dodavanja i brisanja algoritamskih biblioteka koje se koriste za analizu videa. Omogućava analizu rezultata i zapis strukturiranog rezultata na disk koji se mogu koristiti u daljnjoj analizi videa i uređaja za reprodukciju video sadržajaThe demand for a wide range of video and multimedia applications is growing extremely fast in recent years. In such a diverse usage of digital video, there is a need for reliable tool for testing video quality by different parties involved in video content delivery to end users. While video quality methods are gaining quite considerable attention in scientific research, practical tools for video quality are still rare. This thesis presents an application for real-time no-reference video artifact detection that can be used in different scenarios like video equipment testing, network monitoring, video hardware/software development and scientific research. The application has some unique features allowing user customization in terms of used no-reference methods, giving the user deeper insight into the obtained results and easier usage when dealing with in field video equipment testing

Efficient and effective objective image quality assessment metrics

Acquisition, transmission, and storage of images and videos have been largely increased in recent years. At the same time, there has been an increasing demand for high quality images and videos to provide satisfactory quality-of-experience for viewers. In this respect, high dynamic range (HDR) imaging with higher than 8-bit depth has been an interesting approach in order to capture more realistic images and videos. Objective image and video quality assessment plays a significant role in monitoring and enhancing the image and video quality in several applications such as image acquisition, image compression, multimedia streaming, image restoration, image enhancement and displaying. The main contributions of this work are to propose efficient features and similarity maps that can be used to design perceptually consistent image quality assessment tools. In this thesis, perceptually consistent full-reference image quality assessment (FR-IQA) metrics are proposed to assess the quality of natural, synthetic, photo-retouched and tone-mapped images. In addition, efficient no-reference image quality metrics are proposed to assess JPEG compressed and contrast distorted images. Finally, we propose a perceptually consistent color to gray conversion method, perform a subjective rating and evaluate existing color to gray assessment metrics. Existing FR-IQA metrics may have the following limitations. First, their performance is not consistent for different distortions and datasets. Second, better performing metrics usually have high complexity. We propose in this thesis an efficient and reliable full-reference image quality evaluator based on new gradient and color similarities. We derive a general deviation pooling formulation and use it to compute a final quality score from the similarity maps. Extensive experimental results verify high accuracy and consistent performance of the proposed metric on natural, synthetic and photo retouched datasets as well as its low complexity. In order to visualize HDR images on standard low dynamic range (LDR) displays, tone-mapping operators are used in order to convert HDR into LDR. Given different depth bits of HDR and LDR, traditional FR-IQA metrics are not able to assess the quality of tone-mapped images. The existing full-reference metric for tone-mapped images called TMQI converts both HDR and LDR to an intermediate color space and measure their similarity in the spatial domain. We propose in this thesis a feature similarity full-reference metric in which local phase of HDR is compared with the local phase of LDR. Phase is an important information of images and previous studies have shown that human visual system responds strongly to points in an image where the phase information is ordered. Experimental results on two available datasets show the very promising performance of the proposed metric. No-reference image quality assessment (NR-IQA) metrics are of high interest because in the most present and emerging practical real-world applications, the reference signals are not available. In this thesis, we propose two perceptually consistent distortion-specific NR-IQA metrics for JPEG compressed and contrast distorted images. Based on edge statistics of JPEG compressed images, an efficient NR-IQA metric for blockiness artifact is proposed which is robust to block size and misalignment. Then, we consider the quality assessment of contrast distorted images which is a common distortion. Higher orders of Minkowski distance and power transformation are used to train a low complexity model that is able to assess contrast distortion with high accuracy. For the first time, the proposed model is used to classify the type of contrast distortions which is very useful additional information for image contrast enhancement. Unlike its traditional use in the assessment of distortions, objective IQA can be used in other applications. Examples are the quality assessment of image fusion, color to gray image conversion, inpainting, background subtraction, etc. In the last part of this thesis, a real-time and perceptually consistent color to gray image conversion methodology is proposed. The proposed correlation-based method and state-of-the-art methods are compared by subjective and objective evaluation. Then, a conclusion is made on the choice of the objective quality assessment metric for the color to gray image conversion. The conducted subjective ratings can be used in the development process of quality assessment metrics for the color to gray image conversion and to test their performance

Repousser les limites de l'identification faciale en contexte de vidéo-surveillance

Les systèmes d'identification de personnes basés sur le visage deviennent de plus en plus répandus et trouvent des applications très variées, en particulier dans le domaine de la vidéosurveillance. Or, dans ce contexte, les performances des algorithmes de reconnaissance faciale dépendent largement des conditions d'acquisition des images, en particulier lorsque la pose varie mais également parce que les méthodes d'acquisition elles mêmes peuvent introduire des artéfacts. On parle principalement ici de maladresse de mise au point pouvant entraîner du flou sur l'image ou bien d'erreurs liées à la compression et faisant apparaître des effets de blocs. Le travail réalisé au cours de la thèse porte donc sur la reconnaissance de visages à partir d'images acquises à l'aide de caméras de vidéosurveillance, présentant des artéfacts de flou ou de bloc ou bien des visages avec des poses variables. Nous proposons dans un premier temps une nouvelle approche permettant d'améliorer de façon significative la reconnaissance des visages avec un niveau de flou élevé ou présentant de forts effets de bloc. La méthode, à l'aide de métriques spécifiques, permet d'évaluer la qualité de l'image d'entrée et d'adapter en conséquence la base d'apprentissage des algorithmes de reconnaissance. Dans un second temps, nous nous sommes focalisés sur l'estimation de la pose du visage. En effet, il est généralement très difficile de reconnaître un visage lorsque celui-ci n'est pas de face et la plupart des algorithmes d'identification de visages considérés comme peu sensibles à ce paramètre nécessitent de connaître la pose pour atteindre un taux de reconnaissance intéressant en un temps relativement court. Nous avons donc développé une méthode d'estimation de la pose en nous basant sur des méthodes de reconnaissance récentes afin d'obtenir une estimation rapide et suffisante de ce paramètre.The person identification systems based on face recognition are becoming increasingly widespread and are being used in very diverse applications, particularly in the field of video surveillance. In this context, the performance of the facial recognition algorithms largely depends on the image acquisition context, especially because the pose can vary, but also because the acquisition methods themselves can introduce artifacts. The main issues are focus imprecision, which can lead to blurred images, or the errors related to compression, which can introduce the block artifact. The work done during the thesis focuses on facial recognition in images taken by video surveillance cameras, in cases where the images contain blur or block artifacts or show various poses. First, we are proposing a new approach that allows to significantly improve facial recognition in images with high blur levels or with strong block artifacts. The method, which makes use of specific noreference metrics, starts with the evaluation of the quality level of the input image and then adapts the training database of the recognition algorithms accordingly. Second, we have focused on the facial pose estimation. Normally, it is very difficult to recognize a face in an image taken from another viewpoint than the frontal one and the majority of facial identification algorithms which are robust to pose variation need to know the pose in order to achieve a satisfying recognition rate in a relatively short time. We have therefore developed a fast and satisfying pose estimation method based on recent recognition techniques.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF