DNANet: Dense Nested Attention Network for Single Image Dehazing

In this paper, we propose an innovative approach, called Dense Nested Attention Network (DNANet), to directly restore a clear image from a hazy image with a new topology of connection paths. Firstly, through dense nested connections from inside to outside, the DNANet can fuse both shallow and deep features from fine to coarse, then strengthen the feature propagation and reuse to a large extent. We use stacked dilated convolutions, as the basic operation, to alleviate the shortcomings of the traditional context information aggregation methods. Secondly, we examine the weakness of skipping connections by reasoning the existence of residual haze from the shallow to deep layers in the neural network. To address this problem, we use the attention mechanism to filter out the output of residual haze by capturing the information relations on the entire skip feature maps. Thirdly, we introduce an adjustable loss constraint on each block of the outermost nested structure to gather more accurate features. The result demonstrates that DNANet outperforms state-of-the-art methods by a large margin on the benchmark datasets in extensive experiments.