Hallucinating optimal high-dimensional subspaces

Linear subspace representations of appearance variation are pervasive in computer vision. This paper addresses the problem of robustly matching such subspaces (computing the similarity between them) when they are used to describe the scope of variations within sets of images of different (possibly greatly so) scales. A naive solution of projecting the low-scale subspace into the high-scale image space is described first and subsequently shown to be inadequate, especially at large scale discrepancies. A successful approach is proposed instead. It consists of (i) an interpolated projection of the low-scale subspace into the high-scale space, which is followed by (ii) a rotation of this initial estimate within the bounds of the imposed ``downsampling constraint''. The optimal rotation is found in the closed-form which best aligns the high-scale reconstruction of the low-scale subspace with the reference it is compared to. The method is evaluated on the problem of matching sets of (i) face appearances under varying illumination and (ii) object appearances under varying viewpoint, using two large data sets. In comparison to the naive matching, the proposed algorithm is shown to greatly increase the separation of between-class and within-class similarities, as well as produce far more meaningful modes of common appearance on which the match score is based.Comment: Pattern Recognition, 201

Face image super-resolution using 2D CCA

In this paper a face super-resolution method using two-dimensional canonical correlation analysis (2D CCA) is presented. A detail compensation step is followed to add high-frequency components to the reconstructed high-resolution face. Unlike most of the previous researches on face super-resolution algorithms that first transform the images into vectors, in our approach the relationship between the high-resolution and the low-resolution face image are maintained in their original 2D representation. In addition, rather than approximating the entire face, different parts of a face image are super-resolved separately to better preserve the local structure. The proposed method is compared with various state-of-the-art super-resolution algorithms using multiple evaluation criteria including face recognition performance. Results on publicly available datasets show that the proposed method super-resolves high quality face images which are very close to the ground-truth and performance gain is not dataset dependent. The method is very efficient in both the training and testing phases compared to the other approaches. © 2013 Elsevier B.V

A unified framework for subspace based face recognition.

Wang Xiaogang.Thesis (M.Phil.)--Chinese University of Hong Kong, 2003.Includes bibliographical references (leaves 88-91).Abstracts in English and Chinese.Abstract --- p.iAcknowledgments --- p.vTable of Contents --- p.viList of Figures --- p.viiiList of Tables --- p.xChapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Face recognition --- p.1Chapter 1.2 --- Subspace based face recognition technique --- p.2Chapter 1.3 --- Unified framework for subspace based face recognition --- p.4Chapter 1.4 --- Discriminant analysis in dual intrapersonal subspaces --- p.5Chapter 1.5 --- Face sketch recognition and hallucination --- p.6Chapter 1.6 --- Organization of this thesis --- p.7Chapter Chapter 2 --- Review of Subspace Methods --- p.8Chapter 2.1 --- PCA --- p.8Chapter 2.2 --- LDA --- p.9Chapter 2.3 --- Bayesian algorithm --- p.12Chapter Chapter 3 --- A Unified Framework --- p.14Chapter 3.1 --- PCA eigenspace --- p.16Chapter 3.2 --- Intrapersonal and extrapersonal subspaces --- p.17Chapter 3.3 --- LDA subspace --- p.18Chapter 3.4 --- Comparison of the three subspaces --- p.19Chapter 3.5 --- L-ary versus binary classification --- p.22Chapter 3.6 --- Unified subspace analysis --- p.23Chapter 3.7 --- Discussion --- p.26Chapter Chapter 4 --- Experiments on Unified Subspace Analysis --- p.28Chapter 4.1 --- Experiments on FERET database --- p.28Chapter 4.1.1 --- PCA Experiment --- p.28Chapter 4.1.2 --- Bayesian experiment --- p.29Chapter 4.1.3 --- Bayesian analysis in reduced PCA subspace --- p.30Chapter 4.1.4 --- Extract discriminant features from intrapersonal subspace --- p.33Chapter 4.1.5 --- Subspace analysis using different training sets --- p.34Chapter 4.2 --- Experiments on the AR face database --- p.36Chapter 4.2.1 --- "Experiments on PCA, LDA and Bayes" --- p.37Chapter 4.2.2 --- Evaluate the Bayesian algorithm for different transformation --- p.38Chapter Chapter 5 --- Discriminant Analysis in Dual Subspaces --- p.41Chapter 5.1 --- Review of LDA in the null space of and direct LDA --- p.42Chapter 5.1.1 --- LDA in the null space of --- p.42Chapter 5.1.2 --- Direct LDA --- p.43Chapter 5.1.3 --- Discussion --- p.44Chapter 5.2 --- Discriminant analysis in dual intrapersonal subspaces --- p.45Chapter 5.3 --- Experiment --- p.50Chapter 5.3.1 --- Experiment on FERET face database --- p.50Chapter 5.3.2 --- Experiment on the XM2VTS database --- p.53Chapter Chapter 6 --- Eigentransformation: Subspace Transform --- p.54Chapter 6.1 --- Face sketch recognition --- p.54Chapter 6.1.1 --- Eigentransformation --- p.56Chapter 6.1.2 --- Sketch synthesis --- p.59Chapter 6.1.3 --- Face sketch recognition --- p.61Chapter 6.1.4 --- Experiment --- p.63Chapter 6.2 --- Face hallucination --- p.69Chapter 6.2.1 --- Multiresolution analysis --- p.71Chapter 6.2.2 --- Eigentransformation for hallucination --- p.72Chapter 6.2.3 --- Discussion --- p.75Chapter 6.2.4 --- Experiment --- p.77Chapter 6.3 --- Discussion --- p.83Chapter Chapter 7 --- Conclusion --- p.85Publication List of This Thesis --- p.87Bibliography --- p.8

Diverse Image Generation with Very Low Resolution Conditioning

Traditionnellement, lorsqu’il s’agit de générer des images à haute résolution (HR) à partir d’images à basse résolution (LR), les méthodes proposées jusqu’à maintenant se sont principalement concentrées sur les techniques de super-résolution qui visent à récupérer l’image la plus probable à partir d’une image de basse qualité. En procédant de cette manière, on ignore le fait qu’il existe généralement de nombreuses versions valides d’images HR qui correspondent à une image LR donnée. L’objectif de ce travail est d’obtenir différentes versions d’images HR à partir d’une même image LR en utilisant un modèle adversarial génératif. On aborde ce problème sous deux angles différents. D’abord, on utilise des méthodes de super résolution, où en plus de l’image LR, le générateur peut être paramétré par une variable latente afin de produire différentes variations potentielles de l’image. Un tel conditionnement permet de moduler le générateur entre la récupération de l’image la plus proche de la vérité terrain et de variété d’images possibles. Les résultats démontrent notre supériorité en termes de reconstruction et de variété d’images hallucinées plausible par rapport à d’autres méthodes de l’état de l’art. La deuxième approche s’appuie sur les travaux de traduction d’image à image, en proposant une nouvelle approche où le modèle est conditionné sur une version LR du cible. Plus précisément, notre approche vise à transférer les détails fins d’une image source HR pour les adapter la structure générale, selon la version LR de celle-ci. On génère donc des images HR qui partagent les caractéristiques distinctives de l’image HR et qui correspond à l’image LR de la cible lors de la réduction d’échelle. Cette méthode diffère des méthodes précédentes qui se concentrent plutôt sur la traduction d’un style d’image donné en un contenu cible. Les résultats qualitatifs et quantitatifs démontrent des améliorations en termes de qualité visuelle, de diversité et de couverture par rapport aux méthodes de pointe telles que Stargan-v2.Traditionally, when it comes to generating high-resolution (HR) images from a low-resolution(LR) images, the methods proposed so far have mainly focused on super-resolution techniques that aim at recovering the most probable image from low-quality image. Doing so ignores the fact that there are usually many valid versions of HR images that match a given LR image. The objective of this work is to obtain different versions of HR images from the same LR imageusing a generative adversarial model. We approach this problem from two different angles. First, we use super-resolution methods, where in addition to the LR image, the generator can be parameterized by a latent variable to produce different potential variations of the image. Such a conditioning allows to modulate the generator between retrieving the closest image to the ground truth and a variety of possible images. The results demonstrate our superiority in terms of reconstruction and variety of plausible hallucinated images compared to other state-of-the-art methods. The second approach builds on the work of image-to-image translation, by proposing a new approach where the model is conditioned on a LR version of the target. More precisely, our approach aims at transferring the fine details of an HR source image to fit the general structure, according to the LR version of it. We therefore generate HR images that share the distinctive features of the HR image and match the LR image of the target duringdownscaling. This method differs from previous methods that focus instead on translatinga given image style into target content. Qualitative and quantitative results demonstrate improvements in visual quality, diversity, and coverage over state-of-the-art methods such asStargan-v2

Face Hallucination via Deep Neural Networks.

We firstly address aligned low-resolution (LR) face images (i.e. 16X16 pixels) by designing a discriminative generative network, named URDGN. URDGN is composed of two networks: a generative model and a discriminative model. We introduce a pixel-wise L2 regularization term to the generative model and exploit the feedback of the discriminative network to make the upsampled face images more similar to real ones. We present an end-to-end transformative discriminative neural network (TDN) devised for super-resolving unaligned tiny face images. TDN embeds spatial transformation layers to enforce local receptive fields to line-up with similar spatial supports. To upsample noisy unaligned LR face images, we propose decoder-encoder-decoder networks. A transformative discriminative decoder network is employed to upsample and denoise LR inputs simultaneously. Then we project the intermediate HR faces to aligned and noise-free LR faces by a transformative encoder network. Finally, high-quality hallucinated HR images are generated by our second decoder. Furthermore, we present an end-to-end multiscale transformative discriminative neural network (MTDN) to super-resolve unaligned LR face images of different resolutions in a unified framework. We propose a method that explicitly incorporates structural information of faces into the face super-resolution process by using a multi-task convolutional neural network (CNN). Our method not only uses low-level information (i.e. intensity similarity), but also middle-level information (i.e. face structure) to further explore spatial constraints of facial components from LR inputs images. We demonstrate that supplementing residual images or feature maps with additional facial attribute information can significantly reduce the ambiguity in face super-resolution. To explore this idea, we develop an attribute-embedded upsampling network. In this manner, our method is able to super-resolve LR faces by a large upscaling factor while reducing the uncertainty of one-to-many mappings remarkably. We further push the boundaries of hallucinating a tiny, non-frontal face image to understand how much of this is possible by leveraging the availability of large datasets and deep networks. To this end, we introduce a novel Transformative Adversarial Neural Network (TANN) to jointly frontalize very LR out-of-plane rotated face images (including profile views) and aggressively super-resolve them by 8X, regardless of their original poses and without using any 3D information. Besides recovering an HR face images from an LR version, this thesis also addresses the task of restoring realistic faces from stylized portrait images, which can also be regarded as face hallucination

Learnt quasi-transitive similarity for retrieval from large collections of faces

We are interested in identity-based retrieval of face sets from large unlabelled collections acquired in uncontrolled environments. Given a baseline algorithm for measuring the similarity of two face sets, the meta-algorithm introduced in this paper seeks to leverage the structure of the data corpus to make the best use of the available baseline. In particular, we show how partial transitivity of inter-personal similarity can be exploited to improve the retrieval of particularly challenging sets which poorly match the query under the baseline measure. We: (i) describe the use of proxy sets as a means of computing the similarity between two sets, (ii) introduce transitivity meta-features based on the similarity of salient modes of appearance variation between sets, (iii) show how quasi-transitivity can be learnt from such features without any labelling or manual intervention, and (iv) demonstrate the effectiveness of the proposed methodology through experiments on the notoriously challenging YouTube database.Postprin