Coarse-to-Fine Image Super-Resolution Using Convolutional Neural Networks

Convolutional neural networks (CNNs) have been widely applied to computer vision fields due to its excellent performance. CNN-based single image super resolution (SR) methods are also put into practice and outperform previous methods. In this paper, we propose a coarse-to-fine CNN method to boost the existing CNN-based SR methods. We design a cascaded CNN architecture with three stages. The first stage takes the low-resolution (LR) image as the input and outputs a high-resolution (HR) image, then the next stage similarly takes the high-resolution result as the input and produces a finer HR image. Finally, the last stage can obtain the finest HR image. Our architecture is trained as one entire CNN which combines three loss functions to optimize the gradient descent procedure. Experiments on ImageNet-based training samples validates the effectiveness of our method on the public benchmark datasets.