Despite the remarkable success of modern monocular depth estimation methods, the accuracy achievable from a single image is limited, making it is practically useful to incorporate other sources of depth information. Currently, depth estimation from different combinations of sources are treated as different applications, and solved via separate networks trained to use the set of available sources as input for each application. In this paper, we propose a common versatile model that outputs a probability distribution over scene depth given an input color image, as a sample approximation using outputs from a conditional GAN. This distributional output is useful even in the monocular setting, and can be used to estimate depth, pairwise ordering, etc. More importantly, these outputs can be combined with a variety of other depth cues---such as user guidance and partial measurements---for use in different application settings, without retraining. We demonstrate the efficacy of our approach through experiments on the NYUv2 dataset for a number of tasks, and find that our results from a common model, trained only once, are comparable to those from state-of-the-art methods with separate task-specific models.
In this work, we use a more general form for the conditional joint distribution of depth values in local regions. We train a conditional GAN @cite_26 @cite_2 to produce multiple estimates of depth in local patches from an image input. Conditional GANs have been used to produce outputs that are more natural'' than those from networks trained with regression loss alone @cite_36 . In our case, we run our GAN model multiple times to generate multiple plausible estimates, treat these as samples from a distribution, and use these samples to approximate the distribution itself.
@cite_36 @cite_26 @cite_2
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Traditional generative adversarial networks (GAN) and many of its variants are trained by minimizing the KL or JS-divergence loss that measures how close the generated data distribution is from the true data distribution. A recent advance called the WGAN based on Wasserstein distance can improve on the KL and JS-divergence based GANs, and alleviate the gradient vanishing, instability, and mode collapse issues that are common in the GAN training. In this work, we aim at improving on the WGAN by first generalizing its discriminator loss to a margin-based one, which leads to a better discriminator, and in turn a better generator, and then carrying out a progressive training paradigm involving multiple GANs to contribute to the maximum margin ranking loss so that the GAN at later stages will improve upon early stages. We call this method Gang of GANs (GoGAN). We have shown theoretically that the proposed GoGAN can reduce the gap between the true data distribution and the generated data distribution by at least half in an optimally trained WGAN. We have also proposed a new way of measuring GAN quality which is based on image completion tasks. We have evaluated our method on four visual datasets: CelebA, LSUN Bedroom, CIFAR-10, and 50K-SSFF, and have seen both visual and quantitative improvement over baseline WGAN. We introduce scGAN, a novel extension of conditional Generative Adversarial Networks (GAN) tailored for the challenging problem of shadow detection in images. Previous methods for shadow detection focus on learning the local appearance of shadow regions, while using limited local context reasoning in the form of pairwise potentials in a Conditional Random Field. In contrast, the proposed adversarial approach is able to model higher level relationships and global scene characteristics. We train a shadow detector that corresponds to the generator of a conditional GAN, and augment its shadow accuracy by combining the typical GAN loss with a data loss term. Due to the unbalanced distribution of the shadow labels, we use weighted cross entropy. With the standard GAN architecture, properly setting the weight for the cross entropy would require training multiple GANs, a computationally expensive grid procedure. In scGAN, we introduce an additional sensitivity parameter w to the generator. The proposed approach effectively parameterizes the loss of the trained detector. The resulting shadow detector is a single network that can generate shadow maps corresponding to different sensitivity levels, obviating the need for multiple models and a costly training procedure. We evaluate our method on the large-scale SBU and UCF shadow datasets, and observe up to 17 error reduction with respect to the previous state-of-the-art method. Conditional Generative Adversarial Networks (GANs) for cross-domain image-to-image translation have made much progress recently [7, 8, 21, 12, 4, 18]. Depending on the task complexity, thousands to millions of labeled image pairs are needed to train a conditional GAN. However, human labeling is expensive, even impractical, and large quantities of data may not always be available. Inspired by dual learning from natural language translation [23], we develop a novel dual-GAN mechanism, which enables image translators to be trained from two sets of unlabeled images from two domains. In our architecture, the primal GAN learns to translate images from domain U to those in domain V, while the dual GAN learns to invert the task. The closed loop made by the primal and dual tasks allows images from either domain to be translated and then reconstructed. Hence a loss function that accounts for the reconstruction error of images can be used to train the translators. Experiments on multiple image translation tasks with unlabeled data show considerable performance gain of DualGAN over a single GAN. For some tasks, DualGAN can even achieve comparable or slightly better results than conditional GAN trained on fully labeled data. Estimating depth from a single image is a very challenging and exciting topic in computer vision with implications in several application domains. Recently proposed deep learning approaches achieve outstanding results by tackling it as an image reconstruction task and exploiting geometry constraints (e.g., epipolar geometry) to obtain supervisory signals for training. Inspired by these works and compelling results achieved by Generative Adversarial Network (GAN) on image reconstruction and generation tasks, in this paper we propose to cast unsupervised monocular depth estimation within a GAN paradigm. The generator network learns to infer depth from the reference image to generate a warped target image. At training time, the discriminator network learns to distinguish between fake images generated by the generator and target frames acquired with a stereo rig. To the best of our knowledge, our proposal is the first successful attempt to tackle monocular depth estimation with a GAN paradigm and the extensive evaluation on CityScapes and KITTI datasets confirm that it enables to improve traditional approaches. Additionally, we highlight a major issue with data deployed by a standard evaluation protocol widely used in this field and fix this problem using a more reliable dataset recently made available by the KITTI evaluation benchmark.