Improving shape from shading with interactive Tabu search

Optimisation based shape from shading (SFS) is sensitive to initialization: errors in initialization are a significant cause of poor overall shape reconstruction. In this paper, we present a method to help overcome this problem by means of user interaction. There are two key elements in our method. Firstly, we extend SFS to consider a set of initializations, rather than to use a single one. Secondly, we efficiently explore this initialization space using a heuristic search method, tabu search, guided by user evaluation of the reconstruction quality. Reconstruction results on both synthetic and real images demonstrate the effectiveness of our method in providing more desirable shape reconstructions

A unified approach to the well-posedness of some non-Lambertian models in Shape-from-Shading theory

In this paper we show that the introduction of an attenuation factor in the %image irradiance brightness equations relative to various perspective Shape from Shading models allows to make the corresponding differential problems well-posed. We propose a unified approach based on the theory of viscosity solution and we show that the brightness equations with the attenuation term admit a unique viscosity solution. We also discuss in detail the possible boundary conditions that we can use for the Hamilton-Jacobi equations associated to these models

Classification of skin hyper-pigmentation lesions with multi-spectral images

According to clinical protocols, skin diseases are quantified by dermatologists throughout a treatment period, and then a statistical test on these measures allows to evaluate a treatment efficacy. The first step of this process it to classify pathological interest areas. This task is challenging due to the high variability of the images in one clinical data set. In this report, we first review algorithms that exist in the literature and adapt them to our problem. Then we choose the more appropriate algorithm to design a classification strategy. Thereby, we propose to use data reduction combined with SVM to do a first classification of the disease. Then we associate the obtained classification map with a segmentation map in an "interactive classification tool" in order to compromise between operator dependency and algorithm robustness

Occlusion handling in correlation-based matching

In binocular stereovision, the accuracy of the 3D reconstruction depends on the accuracy of matching results. Consequently, matching is an important task. Our first goal is to present a state of the art of matching methods. We define a generic and complete algorithm based on essential components to describe most of the matching methods. Occlusions are one of the most important difficulties and we also present a state of the art of methods dealing with occlusions. Finally, we propose matching methods using two correlation measures to take into account occlusions. The results highlight the best method that merges two disparity maps obtained with two different measures.En stéréovision binoculaire, la mise en correspondance est une étape cruciale pour réaliser la reconstruction 3D de la scène. De très nombreuses publications traitent ce problème. Ainsi, le premier objectif est de proposer un état de l'art des méthodes de mise en correspondance. Nous synthétisons cette étude en présentant un algorithme générique complet faisant intervenir des éléments constituants permettant de décrire les différentes étapes de la recherche de correspondances. Une des plus grandes difficultés, au cours de l'appariement, provient des occultations. C'est pourquoi le second objectif est de présenter un état de l'art des méthodes qui prennent en compte cette difficulté. Enfin, le dernier objectif est de présenter de nouvelles méthodes hybrides, dans le cadre des méthodes locales à base de corrélation. Nous nous appuyons sur l'utilisation de deux mesures de corrélation permettant de mieux prendre en compte le problème des occultations. Les résultats mettent en évidence la meilleure méthode qui consiste à fusionner deux cartes de disparités obtenues avec des mesures différentes

A PDE approach to Shape from Shading via Photometric Stereo

We present a new analytic and numerical approach to the shape from shading using photometric stereo technique. That is, we solve the problem to find the 3D surface of an object starting from its several 2D pictures taken from the same point of view, but changing, for every image, the direction of the light source

A Multiresolution Approach for Shape from Shading Coupling Deterministic and Stochastic Optimization,” technical report

Abstract—Shape from shading is an ill-posed inverse problem for which there is no completely satisfactory solution in the existing literature. In this paper, we address shape from shading as an energy minimization problem. We first show that the deterministic approach provides efficient algorithms in terms of CPU time, but reaches its limits since the energy associated with shape from shading can contain multiple deep local minima. We derive an alternative stochastic approach using simulated annealing. The obtained results strongly outperform the results of the deterministic approach. The shortcoming is an extreme slowness of the optimization. Therefore, we propose a hybrid approach which combines the deterministic and stochastic approaches in a multiresolution framework. Index Terms—Shape from shading, optimization, simulated annealing, multiresolution.