Comparative analysis and implementation of structured edge active contour

This paper proposes modified chanvese model which can be implemented on image for segmentation. The structure of paper is based on Linear structure tensor (LST) as input to the variant model. Structure tensor is a matrix illustration of partial derivative information. In the proposed model, the original image is considered as information channel for computing structure tensor. Difference of Gaussian (DOG) is featuring improvement in which we can get less blurred image than original image.In this paper LST is modified by adding intensity information to enhance orientation information. Finally Active Contour Model (ACM) is used to segment the images. The proposed algorithm is tested on various images and also on some images which have intensity inhomogeneity and results are shown. Also, the results with other algorithms like chanvese, Bhattacharya, Gabor based chanvese and Novel structure tensor based model are compared.It is verified that accuracy of proposed model is the best. The biggest advantage of proposed model is clear edge enhancement

CM-GAN: Image Inpainting with Cascaded Modulation GAN and Object-Aware Training

Recent image inpainting methods have made great progress but often struggle to generate plausible image structures when dealing with large holes in complex images. This is partially due to the lack of effective network structures that can capture both the long-range dependency and high-level semantics of an image. To address these problems, we propose cascaded modulation GAN (CM-GAN), a new network design consisting of an encoder with Fourier convolution blocks that extract multi-scale feature representations from the input image with holes and a StyleGAN-like decoder with a novel cascaded global-spatial modulation block at each scale level. In each decoder block, global modulation is first applied to perform coarse semantic-aware structure synthesis, then spatial modulation is applied on the output of global modulation to further adjust the feature map in a spatially adaptive fashion. In addition, we design an object-aware training scheme to prevent the network from hallucinating new objects inside holes, fulfilling the needs of object removal tasks in real-world scenarios. Extensive experiments are conducted to show that our method significantly outperforms existing methods in both quantitative and qualitative evaluation.Comment: 32 pages, 18 figure

Von Pixeln zu Regionen: Partielle Differentialgleichungen in der Bildanalyse

This work deals with applications of partial differential equations in image analysis. The focus is thereby on applications that can be used for image segmentation. This includes, among other topics, nonlinear diffusion, motion analysis, and image segmentation itself. From each chapter to the next, the methods are directed more and more to image segmentation. While Chapter 2 presents general denoising and simplification techniques, Chapter 4 already addresses the somewhat more special task to extract texture and motion from images. This is in order to employ the resulting features to the partitioning of images finally in Chapter 5. Thus, in this work, one can clearly make out the thread from the raw image data, the pixels, to the more abstract descriptions of images by means of regions. The fact that image processing techniques can also be useful in research areas besides conventional images is shown in Chapter 3. They are used here in order to improve numerical methods for conservation laws in physics. The work conceptually focuses on using as many different features as possible for segmentation. This includes besides image-driven features like texture and motion the knowledge-based information of a three-dimensional object model. The basic idea of this concept is to provide a preferably wide basis of information for separating object regions and thus increasing the number of situations in which the method yields satisfactory segmentation results. A further basic concept pursued in this thesis is to employ coarse-to-fine strategies. They are used both for motion estimation in Chapter 4 and for segmentation in Chapter 5. In both cases one has to deal with optimization problems that contain many local optima. Conventional local optimization therefore usually leads to results the quality of which heavily depends on the initialization. This situation can often be eased, if the optimization problem is first significantly simplified. One then tries to solve the original problem by continuously increasing the problem complexity. Apart from this, the work contains several essential technical novelties. In Chapter 2, nonlinear diffusion with unbounded diffusivities is considered. This also includes total variation flow(TV flow). A thorough analysis of TV flow thereby leads to an analytic solution that allows to show that TV flow is in the space-discrete, one-dimensional setting exactly identical to the corresponding variational approach called TV regularization. Moreover, various different numerical methods are investigated in order to determine their suitability for diffusion filters with unbounded diffusivities. TV flow can be regarded as an alternative to Gaussian smoothing, though there is the significant difference of TV flow being discontinuity preserving. By replacing Gaussian smoothing by TV flow, one can develop new discontinuity preserving versions of well-known operators such as the structure tensor. TV flow is also employed in Chapter 3 where the goal is to improve numerical schemes for the approximation of hyperbolic conservation laws by means of image processing techniques. The role of TV flow in this scope is to remove oscillations of a second order method. In an alternative approach, the approximation performance of a first order method is improved by a nonlinear inverse diffusion filter. The underlying concept is to remove exactly the amount of numerical diffusion that actually stabilizes the scheme. By means of an appropriate stabilization of the inverse diffusion process it is possible to preserve the positive stability properties of the original method. III IV Abstract Chapter 4 is separated into two parts. The first part deals with the extraction of texture features, whereas the second part focuses on motion estimation. Goal of the texture extraction method is to derive a feature space that is as low-dimensional as possible but still provides very good discrimination properties. The basic framework of this feature space is the structure tensor based on TV flow presented earlier in Chapter 2. It contains the orientation, magnitude, and homogeneity of a texture and therefore provides already very important features for texture discrimination. Additionally, a region based local scale measure is developed that supplements the size of texture elements to the feature space. This feature space is used later in Chapter 5 for texture segmentation. Two motion estimation methods are introduced in Chapter 4. One of them is based on the structure tensor from Section 2 and improves existing local methods. The other technique is based on a global variational approach. It differs from usual variational approaches by the use of a gradient constancy assumption. This assumption provides the method with the capability to yield good estimation results even in the presence of small local or global variations of illumination. Besides this novelty, the combination of non-linearized constancy assumptions and a coarse-to-fine strategy yields a numerical scheme that provides for the first time a well founded theory for the very successful warping methods. The described technique leads to results that are generally more accurate than all results presented in literature so far. As already mentioned, goal of the image segmentation approach in Chapter 5 is mainly to integrate the features derived in Chapter 4 and to utilize a coarse-to-fine strategy. This is done in the framework of region based, implicit active contour models which are set up on the concept of level sets. The involved region models are extended by nonparametric as well as local region statistics. A further novelty is the extension of the level set concept to multiple regions. The optimum number of regions is thereby estimated by a hierarchical approach. This is a considerable extension of conventional active contour models, which are usually restricted to two regions. Moreover, the idea to use three-dimensional object knowledge for segmentation is presented. The proposed method uses the extracted contour for estimating the pose of the object, while in return the projected object model supports the segmentation. The implementation of this idea as described in this thesis is only at an early stage. Plenty of interesting aspects can be derived from this concept that are to be investigated in the future.Die vorliegenden Arbeit beschäftigt sich mit Anwendungen partieller Differentialgleichungen in der Bildanalyse. Dabei stehen Anwendungen im Vordergrund, die sich zur Bildsegmentierung verwenden lassen. Dies schließt unter anderem nichtlineare Diffusion, Bewegungsschätzung und die Bildsegmentierung selbst ein. Von Kapitel zu Kapitel werden die verwendeten Methoden dabei mehr und mehr auf die Bildsegmentierung ausgerichtet. Werden in Kapitel 2 noch allgemeine Entrauschungs- und Bildvereinfachungsoperationen vorgestellt, behandelt Kapitel 4 die schon etwas speziellere Aufgabe, Textur und Bewegung aus Bildern zu extrahieren, um entsprechende Merkmale schließlich in Kapitel 5 zur Segmentierung von Bildern verwenden zu können. Dabei zieht sich der Weg von den rohen Bilddaten, den Pixeln, hin zur abstrakteren Beschreibung von Bildern mit Hilfe von Regionen als roter Faden durch die gesamte Arbeit. Dass sich Bildverarbeitungstechniken auch in Forschungsgebieten fern herkömmlicher Bilder als nützlich erweisen können, zeigt Kapitel 3. Hier werden Bildverarbeitungstechniken zur Verbesserung numerischer Verfahren für Erhaltungsgleichungen der Physik verwendet. Konzeptionell legt diese Arbeit Wert darauf, möglichst viele verschiedene Merkmale zur Segmentierung zu verwenden. Darunter fallen neben den bildgestützten Merkmalen wie Textur und Bewegung auch die wissensbasierte Information eines dreidimensionalen Oberflächenmodells. Die prinzipielle Idee hinter diesem Konzept ist, die Entscheidungsgrundlage zur Trennung von Objektregionen auf eine möglichst breite Informationsbasis zu stellen und somit die Anzahl der Situationen, in denen das Verfahren zufriedenstellende Segmentierungsergebnisse liefert, zu erhöhen. Ein weiteres Grundkonzept, das in dieser Arbeit verfolgt wird, ist die Verwendung von Coarse- To-Fine-Strategien. Sie kommen sowohl bei der Bewegungsschätzung in Kapitel 4 als auch in der Segmentierung in Kapitel 5 zum Einsatz. In beiden Fällen hat man es mit Optimierungsproblemen zu tun, die viele lokale Optima aufweisen. Herkömmliche lokale Optimierung führt daher meist zu Ergebnissen, deren Qualität stark von der Initialisierung abhängt. Diese Situation lässt sich häufig entschärfen, wenn man das entsprechende Optimierungsproblem zunächst deutlich vereinfacht und erst nach und nach das ursprüngliche Problem zu lösen versucht. Daneben enthält diese Arbeit viele wesentliche technische Neuerungen. In Kapitel 2 wird nichtlineare Diffusion mit unbeschränkten Diffusivitäten betrachtet, was auch Total-Variation- Flow (TV-Flow) mit einschließt. Eine genaue Analyse von TV-Flow führt dabei zu einer analytischen Lösung, mit Hilfe derer man zeigen kann, dass TV-Flow im diskreten, eindimensionalen Fall exakt identisch mit dem ensprechenden Variationsansatz der TV-Regularisierung ist. Desweiteren werden verschiedene numerische Verfahren in Bezug auf ihre Eignung für Diffusionsfilter mit unbeschränkten Diffusivitäten untersucht. Man kann TV-Flow als eine Alternative zur Gaußglättung ansehen, mit dem entscheidenden Unterschied, dass TV-Flow kantenerhaltend ist. Durch Ersetzen von Gaußglättung durch TV-Flow lassen sich so diskontinuitätserhaltende Varianten bekannter Operatoren wie etwa des Strukturtensors entwickeln. Auch in Kapitel 3 kommt TV-Flow zum Einsatz, wenn es darum geht, numerische Verfahren zur Approximation hyperbolischer Erhaltungsgleichungen durch Bildverarbeitungsmethoden zu verbessern. TV-Flow fällt dabei die Rolle zu, Oszillationen eines Verfahrens zweiter Ordnung zu beseitigen. In einem alternativen Ansatz werden die Approximationseigenschaften eines Verfahrens erster Ordnung durch einen nichtlinearen Rückwärtsdiffusionsfilter verbessert, indem die numerische Diffusion, die das Verfahren eigentlich stabilisiert, gezielt wieder entfernt wird. Dabei gelingt es durch eine geeignete Stabilisierung der Rückwärtsdiffusion, die positiven Stabilitätseigenschaften des Originalverfahrens zu erhalten. Kapitel 4 spaltet sich in zwei Teile auf, wobei der erste Teil von der Extrahierung von Texturmerkmalen handelt, während sich der zweite Teil auf Bewegungsschätzung konzentriert. Bei den Texturmerkmalen besteht dabei das Ziel, einen möglichst niederdimensionalen Merkmalsraum zu kreieren, der dennoch sehr gute Diskriminierungseigenschaften besitzt. Das Grundgerüst dieses Merkmalsraums stellt dabei der in Kapitel 2 vorgestellte, auf TV-Flow basierende Strukturtensor dar. Er beschreibt mit der Orientierung, Stärke und Homogenität der Texturierung bereits sehr wichtige Merkmale einer Textur. Daneben wird ein regionenbasiertes, lokales Skalenmaß entwickelt, das zusätzlich die Größe von Texturelementen als Merkmal einbringt. Diese Texturmerkmale werden später in Kapitel 5 zur Textursegmentierung verwendet. Zur Bewegungsschätzung werden zwei Verfahren vorgestellt. Das eine basiert auf dem in Kapitel 2 eingeführten Strukturtensor und stellt eine Verbesserung vorhandener lokaler Methoden dar. Das andere Verfahren basiert auf einem globalen Variationsansatz und unterscheidet sich von üblichen Variationsansätzen durch die Verwendung einer Gradientenkonstanzannahme. Diese stattet das Verfahren mit der Fähigkeit aus, auch beim Vorhandensein kleinerer lokaler oder globaler Helligkeitsschwankungen gute Schätzergebnisse zu liefern. Daneben ergibt sich aus der Kombination von nicht-linearisierten Konstanzannahmen und einer Coarse-To-Fine-Strategie ein numerisches Schema, das erstmals eine fundierte Theorie zu den sehr erfolgreichen Warping-Verfahren zur Verfügung stellt. Mit der beschriebenen Technik werden Ergebnisse erzielt, die grundsätzlich präziser sind als alles was bisher in der Literatur vorgestellt wurde. Bei der eigentlichen Bildsegmentierung in Kapitel 5 geht es schließlich, wie bereits erwähnt, hauptsächlich um die Einbringung der in Kapitel 4 entwickelten zusätzlichen Merkmale und um die Verwendung einer Coarse-To-Fine-Strategie. Dies geschieht im Rahmen von regionenbasierten, impliziten Aktiv-Kontur-Modellen, die auf dem Konzept der Level-Sets aufbauen. Dabei werden die Regionenmodelle um nichtparametrische und lokale Beschreibungen der Regionenstatistik erweitert. Eine weitere Neuerung ist die Erweiterung des Level-Set-Konzepts auf mehrere Regionen. In einem teils hierarchischen Ansatz wird dabei auch die optimale Anzahl der Regionen geschätzt, was eine erhebliche Erweiterung im Vergleich zu herkömmlichen Aktiv-Kontur- Modellen darstellt. Außerdem wird die Idee vorgestellt, dreidimensionales Objektwissen in der Segmentierung zu verwenden, indem anhand der Segmentierung die Lage des Objekts geschätzt wird und umgekehrt wiederum das projizierte Objektmodell die Segmentierung unterstützt. Die Umsetzung dieser Idee, wie sie in dieser Arbeit beschrieben wird, steht dabei erst am Anfang. Für die Zukunft ergeben sich hieraus noch viele interessanter Aspekte, die es zu untersuchen gilt

Deformable models for adaptive radiotherapy planning

Radiotherapy is the most widely used treatment for cancer, with 4 out of 10 cancer patients receiving radiotherapy as part of their treatment. The delineation of gross tumour volume (GTV) is crucial in the treatment of radiotherapy. An automatic contouring system would be beneficial in radiotherapy planning in order to generate objective, accurate and reproducible GTV contours. Image guided radiotherapy (IGRT) acquires patient images just before treatment delivery to allow any necessary positional correction. Consequently, real-time contouring system provides an opportunity to adopt radiotherapy on the treatment day. In this thesis, freely deformable models (FDM) and shape constrained deformable models (SCDMs) were used to automatically delineate the GTV for brain cancer and prostate cancer. Level set method (LSM) is a typical FDM which was used to contour glioma on brain MRI. A series of low level image segmentation methodologies are cascaded to form a case-wise fully automatic initialisation pipeline for the level set function. Dice similarity coefficients (DSCs) were used to evaluate the contours. Results shown a good agreement between clinical contours and LSM contours, in 93% of cases the DSCs was found to be between 60% and 80%. The second significant contribution is a novel development to the active shape model (ASM), a profile feature was selected from pre-computed texture features by minimising the Mahalanobis distance (MD) to obtain the most distinct feature for each landmark, instead of conventional image intensity. A new group-wise registration scheme was applied to solve the correspondence definition within the training data. This ASM model was used to delineated prostate GTV on CT. DSCs for this case was found between 0.75 and 0.91 with the mean DSC 0.81. The last contribution is a fully automatic active appearance model (AAM) which captures image appearance near the GTV boundary. The image appearance of inner GTV was discarded to spare the potential disruption caused by brachytherapy seeds or gold markers. This model outperforms conventional AAM at the prostate base and apex region by involving surround organs. The overall mean DSC for this case is 0.85

Beyond imaging with coherent anti-Stokes Raman scattering microscopy

La microscopie optique permet de visualiser des échantillons biologiques avec une bonne sensibilité et une résolution spatiale élevée tout en interférant peu avec les échantillons. La microscopie par diffusion Raman cohérente (CARS) est une technique de microscopie non linéaire basée sur l’effet Raman qui a comme avantage de fournir un mécanisme de contraste endogène sensible aux vibrations moléculaires. La microscopie CARS est maintenant une modalité d’imagerie reconnue, en particulier pour les expériences in vivo, car elle élimine la nécessité d’utiliser des agents de contraste exogènes, et donc les problèmes liés à leur distribution, spécificité et caractère invasif. Cependant, il existe encore plusieurs obstacles à l’adoption à grande échelle de la microscopie CARS en biologie et en médecine : le coût et la complexité des systèmes actuels, les difficultés d’utilisation et d’entretient, la rigidité du mécanisme de contraste, la vitesse de syntonisation limitée et le faible nombre de méthodes d’analyse d’image adaptées. Cette thèse de doctorat vise à aller au-delà de certaines des limites actuelles de l’imagerie CARS dans l’espoir que cela encourage son adoption par un public plus large. Tout d’abord, nous avons introduit un nouveau système d’imagerie spectrale CARS ayant une vitesse de syntonisation de longueur d’onde beaucoup plus rapide que les autres techniques similaires. Ce système est basé sur un laser à fibre picoseconde synchronisé qui est à la fois robuste et portable. Il peut accéder à des lignes de vibration Raman sur une plage importante (2700–2950 cm-1) à des taux allant jusqu’à 10 000 points spectrales par seconde. Il est parfaitement adapté pour l’acquisition d’images spectrales dans les tissus épais. En second lieu, nous avons proposé une nouvelle méthode d’analyse d’images pour l’évaluation de la structure de la myéline dans des images de sections longitudinales de moelle épinière. Nous avons introduit un indicateur quantitatif sensible à l’organisation de la myéline et démontré comment il pourrait être utilisé pour étudier certaines pathologies. Enfin, nous avons développé une méthode automatisé pour la segmentation d’axones myélinisés dans des images CARS de coupes transversales de tissu nerveux. Cette méthode a été utilisée pour extraire des informations morphologique des fibres nerveuses dans des images CARS de grande échelle.Optical-based microscopy techniques can sample biological specimens using many contrast mechanisms providing good sensitivity and high spatial resolution while minimally interfering with the samples. Coherent anti-Stokes Raman scattering (CARS) microscopy is a nonlinear microscopy technique based on the Raman effect. It shares common characteristics of other optical microscopy modalities with the added benefit of providing an endogenous contrast mechanism sensitive to molecular vibrations. CARS is now recognized as a great imaging modality, especially for in vivo experiments since it eliminates the need for exogenous contrast agents, and hence problems related to the delivery, specificity, and invasiveness of those markers. However, there are still several obstacles preventing the wide-scale adoption of CARS in biology and medicine: cost and complexity of current systems as well as difficulty to operate and maintain them, lack of flexibility of the contrast mechanism, low tuning speed and finally, poor accessibility to adapted image analysis methods. This doctoral thesis strives to move beyond some of the current limitations of CARS imaging in the hope that it might encourage a wider adoption of CARS as a microscopy technique. First, we introduced a new CARS spectral imaging system with vibrational tuning speed many orders of magnitude faster than other narrowband techniques. The system presented in this original contribution is based on a synchronized picosecond fibre laser that is both robust and portable. It can access Raman lines over a significant portion of the highwavenumber region (2700–2950 cm-1) at rates of up to 10,000 spectral points per second and is perfectly suitable for the acquisition of CARS spectral images in thick tissue. Secondly, we proposed a new image analysis method for the assessment of myelin health in images of longitudinal sections of spinal cord. We introduced a metric sensitive to the organization/disorganization of the myelin structure and showed how it could be used to study pathologies such as multiple sclerosis. Finally, we have developped a fully automated segmentation method specifically designed for CARS images of transverse cross sections of nerve tissue.We used our method to extract nerve fibre morphology information from large scale CARS images

FlowLens: Seeing Beyond the FoV via Flow-guided Clip-Recurrent Transformer

Limited by hardware cost and system size, camera's Field-of-View (FoV) is not always satisfactory. However, from a spatio-temporal perspective, information beyond the camera's physical FoV is off-the-shelf and can actually be obtained "for free" from the past. In this paper, we propose a novel task termed Beyond-FoV Estimation, aiming to exploit past visual cues and bidirectional break through the physical FoV of a camera. We put forward a FlowLens architecture to expand the FoV by achieving feature propagation explicitly by optical flow and implicitly by a novel clip-recurrent transformer, which has two appealing features: 1) FlowLens comprises a newly proposed Clip-Recurrent Hub with 3D-Decoupled Cross Attention (DDCA) to progressively process global information accumulated in the temporal dimension. 2) A multi-branch Mix Fusion Feed Forward Network (MixF3N) is integrated to enhance the spatially-precise flow of local features. To foster training and evaluation, we establish KITTI360-EX, a dataset for outer- and inner FoV expansion. Extensive experiments on both video inpainting and beyond-FoV estimation tasks show that FlowLens achieves state-of-the-art performance. Code will be made publicly available at https://github.com/MasterHow/FlowLens.Comment: Code will be made publicly available at https://github.com/MasterHow/FlowLen

New PDE models for imaging problems and applications

Variational methods and Partial Differential Equations (PDEs) have been extensively employed for the mathematical formulation of a myriad of problems describing physical phenomena such as heat propagation, thermodynamic transformations and many more. In imaging, PDEs following variational principles are often considered. In their general form these models combine a regularisation and a data fitting term, balancing one against the other appropriately. Total variation (TV) regularisation is often used due to its edgepreserving and smoothing properties. In this thesis, we focus on the design of TV-based models for several different applications. We start considering PDE models encoding higher-order derivatives to overcome wellknown TV reconstruction drawbacks. Due to their high differential order and nonlinear nature, the computation of the numerical solution of these equations is often challenging. In this thesis, we propose directional splitting techniques and use Newton-type methods that despite these numerical hurdles render reliable and efficient computational schemes. Next, we discuss the problem of choosing the appropriate data fitting term in the case when multiple noise statistics in the data are present due, for instance, to different acquisition and transmission problems. We propose a novel variational model which encodes appropriately and consistently the different noise distributions in this case. Balancing the effect of the regularisation against the data fitting is also crucial. For this sake, we consider a learning approach which estimates the optimal ratio between the two by using training sets of examples via bilevel optimisation. Numerically, we use a combination of SemiSmooth (SSN) and quasi-Newton methods to solve the problem efficiently. Finally, we consider TV-based models in the framework of graphs for image segmentation problems. Here, spectral properties combined with matrix completion techniques are needed to overcome the computational limitations due to the large amount of image data. Further, a semi-supervised technique for the measurement of the segmented region by means of the Hough transform is proposed

Computational imaging and automated identification for aqueous environments

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2011Sampling the vast volumes of the ocean requires tools capable of observing from a distance while retaining detail necessary for biology and ecology, ideal for optical methods. Algorithms that work with existing SeaBED AUV imagery are developed, including habitat classi fication with bag-of-words models and multi-stage boosting for rock sh detection. Methods for extracting images of sh from videos of longline operations are demonstrated. A prototype digital holographic imaging device is designed and tested for quantitative in situ microscale imaging. Theory to support the device is developed, including particle noise and the effects of motion. A Wigner-domain model provides optimal settings and optical limits for spherical and planar holographic references. Algorithms to extract the information from real-world digital holograms are created. Focus metrics are discussed, including a novel focus detector using local Zernike moments. Two methods for estimating lateral positions of objects in holograms without reconstruction are presented by extending a summation kernel to spherical references and using a local frequency signature from a Riesz transform. A new metric for quickly estimating object depths without reconstruction is proposed and tested. An example application, quantifying oil droplet size distributions in an underwater plume, demonstrates the efficacy of the prototype and algorithms.Funding was provided by NOAA Grant #5710002014, NOAA NMFS Grant #NA17RJ1223, NSF Grant #OCE-0925284, and NOAA Grant #NA10OAR417008