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We present an effective semi-supervised learning algorithm for single image dehazing. The proposed algorithm applies a deep Convolutional Neural Network (CNN) containing a supervised learning branch and an unsupervised learning branch. In the supervised branch, the deep neural network is constrained by the supervised loss functions, which are mean squared, perceptual, and adversarial losses. In the unsupervised branch, we exploit the properties of clean images via sparsity of dark channel and gradient priors to constrain the network. We train the proposed network on both the synthetic data and real-world images in an end-to-end manner. Our analysis shows that the proposed semi-supervised learning algorithm is not limited to synthetic training datasets and can be generalized well to real-world images. Extensive experimental results demonstrate that the proposed algorithm performs favorably against the state-of-the-art single image dehazing algorithms on both benchmark datasets and real-world images. [ABSTRACT FROM AUTHOR]

Highlights • Motion blur kernel size is a significant input parameter of deblurring algorithms. • A regression CNN is proposed to estimate the kernel size of a blurry image. • The kernel size for training is labeled in a relative way. • The kernel size to be estimated can be arbitrary. • The estimated kernel size helps existing deblurring algorithms yielding satisfactory results. Abstract Deblurring is to restore a latent clear image as well as to estimate an underlying blur kernel from a single blurry image. Motion blur kernel size is a significant input parameter of existing deblurring algorithms. Setting the size manually, which is a tedious trial-and-error process, can hardly obtain a satisfactory result directly and effectively. In this paper, we formulate the kernel size estimation as a regression problem and construct a convolutional neural network (CNN) to resolve it. After training the CNN by a large number of simulated blurry images with labels, which are produced by a relative way, we can estimate the kernel sizes of a given blurry image without size limitation. Both quantitative and qualitative results of experiments show that our method can not only estimate the motion blur kernel size accurately but also help to yield better pictures with estimated kernel sizes as input parameters. [ABSTRACT FROM AUTHOR]