A study of deep learning and its applications to face recognition techniques

El siguiente trabajo es el resultado de la tesis de maestría de Fernando Suzacq. La tesis se centró alrededor de la investigación sobre el reconocimiento facial en 3D, sin la reconstrucción de la profundidad ni la utilización de modelos 3D genéricos. Esta investigación resultó en la escritura de un paper y su posterior publicación en IEEE Transactions on Pattern Analysis and Machine Intelligence. Mediante el uso de iluminación activa, se mejora el reconocimiento facial en 2D y se lo hace más robusto a condiciones de baja iluminación o ataques de falsificación de identidad. La idea central del trabajo es la proyección de un patrón de luz de alta frecuencia sobre la cara de prueba. De la captura de esta imagen, nos es posible recuperar información real 3D, que se desprende de las deformaciones de este patrón, junto con una imagen 2D de la cara de prueba. Este proceso evita tener que lidiar con la difícil tarea de reconstrucción 3D. En el trabajo se presenta la teoría que fundamenta este proceso, se explica su construcción y se proveen los resultados de distintos experimentos realizados que sostienen su validez y utilidad. Para el desarrollo de esta investigación, fue necesario el estudio de la teoría existente y una revisión del estado del arte en este problema particular. Parte del resultado de este trabajo se presenta también en este documento, como marco teórico sobre la publicación

Octuplet Loss: Make Face Recognition Robust to Image Resolution

Image resolution, or in general, image quality, plays an essential role in the performance of today's face recognition systems. To address this problem, we propose a novel combination of the popular triplet loss to improve robustness against image resolution via fine-tuning of existing face recognition models. With octuplet loss, we leverage the relationship between high-resolution images and their synthetically down-sampled variants jointly with their identity labels. Fine-tuning several state-of-the-art approaches with our method proves that we can significantly boost performance for cross-resolution (high-to-low resolution) face verification on various datasets without meaningfully exacerbating the performance on high-to-high resolution images. Our method applied on the FaceTransformer network achieves 95.12% face verification accuracy on the challenging XQLFW dataset while reaching 99.73% on the LFW database. Moreover, the low-to-low face verification accuracy benefits from our method. We release our code to allow seamless integration of the octuplet loss into existing frameworks

Schizotypy and facial emotion processing

The ability to accurately interpret facial emotion is crucial to social being and our capacity to correctly interpret threat-related expressions has obvious adaptive value. Healthy individuals appear to process facial emotions rapidly, accurately and effortlessly, while individuals with schizophrenia often present with marked impairment in emotion processing. The hypothesis of continuity between schizophrenia and normal behaviour suggests that the signs and symptoms of the disorder also occur to varying, lesser degrees in the general population. This thesis presents a series of studies that explore the limits of facial emotion processing in healthy individuals, and its relationship with schizotypal personality traits. The first paper describes a set of three studies that use eye tracking techniques to explore the limits of rapid emotion processing. It is shown that we can quickly orient attention towards emotional faces even when the faces are task-irrelevant, presented for very brief intervals, and located well into peripheral vision. The remaining studies explore whether high schizotypes have similarities to individuals with schizophrenia in the way that they process facial emotion. High schizotypes were significantly less accurate at discriminating facial emotions and significantly more likely to misperceive neutral faces as angry, offering support for continuum models of visual hallucinatory experiences. A further study revealed that high relative to low schizoptypes feel as though they are exposed to angry faces for longer. It is argued that this experience itself may serve to maintain hypervigilance to social threat. Finally, laterality biases during face perception were explored. Contrary to the predictions of continuum models of schizophrenia, high schizotypes had an increased left side / right hemisphere bias for face processing. In summary, the thesis offers partial support for the hypothesis of continuity between the impairments in emotion discrimination observed in individuals with schizophrenia, and normal, healthy variation in facial emotion processing

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