Unsupervised Diverse Colorization via Generative Adversarial Networks

Colorization of grayscale images has been a hot topic in computer vision. Previous research mainly focuses on producing a colored image to match the original one. However, since many colors share the same gray value, an input grayscale image could be diversely colored while maintaining its reality. In this paper, we design a novel solution for unsupervised diverse colorization. Specifically, we leverage conditional generative adversarial networks to model the distribution of real-world item colors, in which we develop a fully convolutional generator with multi-layer noise to enhance diversity, with multi-layer condition concatenation to maintain reality, and with stride 1 to keep spatial information. With such a novel network architecture, the model yields highly competitive performance on the open LSUN bedroom dataset. The Turing test of 80 humans further indicates our generated color schemes are highly convincible

NIR image colorization with graph-convolutional neural networks

Colorization of near-infrared (NIR) images is a challenging problem due to the different material properties at the infared wavelenghts, thus reducing the correlation with visible images. In this paper, we study how graph-convolutional neural networks allow exploiting a more powerful inductive bias than standard CNNs, in the form of non-local self-similiarity. Its impact is evaluated by showing how training with mean squared error only as loss leads to poor results with a standard CNN, while the graph-convolutional network produces significantly sharper and more realistic colorizations

Processing and Representation of Multispectral Images Using Deep Learning Techniques

This thesis has implemented innovative techniques in the field of computer vision using visible and near-infrared spectrum images, applying deep learning through convolutional networks, especially GANs' architectures, which are specialists in generating information and also includes meta techniques -learning to tackle the problem of determining the similarity of images of a different spectrum. In this research, with this type of convolutional networks, different supervised and unsupervised techniques have been created to solve challenging problems, like detect the similarity of patches of different spectra (visible-infrared), colorized images of the near-infrared spectrum, estimation of vegetation index (NDVI) and the haze removal present on RGB images using NIR images. For all these techniques different variants of the GAN's networks, such as standard, conditional, stacked, and cyclic have been used. Also, a metric-based meta-learning approach has been implemented. It should be mentioned that together with the implementation of adversarial network models, the use of multiple loss functions has been proposed to improve the generalization and increase the effectiveness of the models. The experiments were performed with paired and unpaired images, given the different supervised and unsupervised architectures implemented, respectively. The experimental results obtained in each of the approaches implemented in the doctoral work compared with the techniques of the state of the art were shown to be more effective