Hourglass Attention Network for Image Inpainting.

Benefiting from the powerful ability of convolutional neural networks (CNNs) to learn semantic information and texture patterns of images, learning-based image inpainting methods have made noticeable breakthroughs over the years. However, certain inherent defects (e.g. local prior, spatially sharing parameters) of CNNs limit their performance when encountering broken images mixed with invalid information. Compared to convolution, attention has a lower inductive bias, and the output is highly correlated with the input, making it more suitable for processing images with various breakage. Inspired by this, in this paper we propose a novel attention-based network (transformer), called hourglass attention network (HAN) for image inpainting, which builds an hourglass-shaped attention structure to generate appropriate features for complemented images. In addition, we design a novel attention called Laplace attention, which introduces a Laplace distance prior for the vanilla multi-head attention, allowing the feature matching process to consider not only the similarity of features themselves, but also distance between features. With the synergy of hourglass attention structure and Laplace attention, our HAN is able to make full use of hierarchical features to mine effective information for broken images. Experiments on several benchmark datasets demonstrate superior performance by our proposed approach. The code can be found at github.com/dengyecode/hourglassattention.