Enhanced Characterness for Text Detection in the Wild

Text spotting is an interesting research problem as text may appear at any random place and may occur in various forms. Moreover, ability to detect text opens the horizons for improving many advanced computer vision problems. In this paper, we propose a novel language agnostic text detection method utilizing edge enhanced Maximally Stable Extremal Regions in natural scenes by defining strong characterness measures. We show that a simple combination of characterness cues help in rejecting the non text regions. These regions are further fine-tuned for rejecting the non-textual neighbor regions. Comprehensive evaluation of the proposed scheme shows that it provides comparative to better generalization performance to the traditional methods for this task

High Relief from Brush Painting

Relief is an art form part way between 3D sculpture and 2D painting. We present a novel approach for generating a texture-mapped high-relief model from a single brush painting. Our aim is to extract the brushstrokes from a painting and generate the individual corresponding relief proxies rather than recovering the exact depth map from the painting, which is a tricky computer vision problem, requiring assumptions that are rarely satisfied. The relief proxies of brushstrokes are then combined together to form a 2.5D high-relief model. To extract brushstrokes from 2D paintings, we apply layer decomposition and stroke segmentation by imposing boundary constraints. The segmented brushstrokes preserve the style of the input painting. By inflation and a displacement map of each brushstroke, the features of brushstrokes are preserved by the resultant high-relief model of the painting. We demonstrate that our approach is able to produce convincing high-reliefs from a variety of paintings(with humans, animals, flowers, etc.). As a secondary application, we show how our brushstroke extraction algorithm could be used for image editing. As a result, our brushstroke extraction algorithm is specifically geared towards paintings with each brushstroke drawn very purposefully, such as Chinese paintings, Rosemailing paintings, etc

Contributions to the Completeness and Complementarity of Local Image Features

Tese de doutoramento em Engenharia Informática apresentada à Faculdade de Ciências e Tecnologia da Universidade de CoimbraLocal image feature detection (or extraction, if we want to use a more semantically correct term) is a central and extremely active research topic in the field of computer vision. Reliable solutions to prominent problems such as matching, content-based image retrieval, object (class) recognition, and symmetry detection, often make use of local image features. It is widely accepted that a good local feature detector is the one that efficiently retrieves distinctive, accurate, and repeatable features in the presence of a wide variety of photometric and geometric transformations. However, these requirements are not always the most important. In fact, not all the applications require the same properties from a local feature detector. We can distinguish three broad categories of applications according to the required properties. The first category includes applications in which the semantic meaning of a particular type of features is exploited. For instance, edge or even ridge detection can be used to identify blood vessels in medical images or watercourses in aerial images. Another example in this category is the use of blob extraction to identify blob-like organisms in microscopic images. A second category includes tasks such as matching, tracking, and registration, which mainly require distinctive, repeatable, and accurate features. Finally, a third category comprises applications such as object (class) recognition, image retrieval, scene classification, and image compression. For this category, it is crucial that features preserve the most informative image content (robust image representation), while requirements such as repeatability and accuracy are of less importance. Our research work is mainly focused on the problem of providing a robust image representation through the use of local features. The limited number of types of features that a local feature extractor responds to might be insufficient to provide the so-called robust image representation. It is fundamental to analyze the completeness of local features, i.e., the amount of image information preserved by local features, as well as the often neglected complementarity between sets of features. The major contributions of this work come in the form of two substantially different local feature detectors aimed at providing considerably robust image representations. The first algorithm is an information theoretic-based keypoint extraction that responds to complementary local structures that are salient (highly informative) within the image context. This method represents a new paradigm in local feature extraction, as it introduces context-awareness principles. The second algorithm extracts Stable Salient Shapes, a novel type of regions, which are obtained through a feature-driven detection of Maximally Stable Extremal Regions (MSER). This method provides compact and robust image representations and overcomes some of the major shortcomings of MSER detection. We empirically validate the methods by investigating the repeatability, accuracy, completeness, and complementarity of the proposed features on standard benchmarks. Under these results, we discuss the applicability of both methods

Some Thermodynamical Aspects of String Theory

Thermodynamical aspects of string theory are reviewed and discussed.Comment: 22 Pages plain latex; based on contributions to Golfand Memorial Volume and Englertfest by E.Rabinovic

Lovelock gravity, black holes and holography

Lovelock theory is the natural extension of General Relativity to higher di- mensions and can also be thought of as a toy model for ghost-free higher curvature gravity. These gravity theories capture some of the de ning fea- tures of higher curvature gravities, namely the existence of more than one (A)dS vacuum and an intricate dynamics, more general black hole solutions and instabilities; while avoiding some of their problems. In particular, Love- lock gravities yield second order eld equations so that they can be considered beyond the perturbative regime and are free of higher derivative ghosts. This provides an appealing arena to explore di erent gravitational and holographic aspects of higher curvature gravity. Most of the vacua of the theory support black holes that display inter- esting features. Besides, black holes with maximally symmetric horizons are subject to a version of Birkho 's theorem and their solutions can be found analytically. Most e orts in the literature have been devoted however to one particular branch of solutions, often restricted to a speci c combination of the Lovelock couplings. The branch usually chosen for the analysis is the so- called EH-branch, as it actually reduces to the general relativistic solution as we turn o the higher order couplings. In this thesis we have presented some tools that allow for the description of Lovelock black holes for arbitrary values of the whole set of couplings, dimensionality and order of the theory. Despite the fact of the solution being implicit, it is possible to extract most relevant information and discuss all possible cases in the general situation, analyze the number of horizons, the thermodynamic stability of the solution, phase transitions, etc. Furthermore, this approach has been generalized to the case of charged and cosmological solutions, and also to the so called quasi-topological gravities, that share the same functional form of the black hole solutions with the Lovelock family while being lower dimensional. Our method is very useful to gain intuition about physical processes in- volving black holes. One can easily visualize the evolution of the position and number of horizons as the mass of the solution varies, this providing crucial information about, for instance, the possible appearance of naked singulari- ties or the violation of the third law of thermodynamics. We have seen that the rigid symmetry imposed on the solution naively allows such problematic behavior which is avoided once the stability of the solution is taken into full consideration

Localized Backreacted Flavor Branes in Holographic QCD

We investigate the perturbative (in $g_s N_{D8}$) backreaction of localized D8 branes in D4-D8 systems including in particular the Sakai Sugimoto model. We write down the explicit expressions of the backreacted metric, dilaton and RR form. We find that the backreaction remains small up to a radial value of $u \ll \ell_s/(g_s N_{D8})$, and that the background functions are smooth except at the D8 sources. In this perturbative window, the original embedding remains a solution to the equations of motion. Furthermore, the fluctuations around the original embedding, describing scalar mesons, do not become tachyonic due to the backreaction in the perturbative regime. This is is due to a cancelation between the DBI and CS parts of the D8 brane action in the perturbed background.Comment: 1+48 pages (7 figures) + 15 pages, citations added & minor correction