Coarse-to-Fine Image DeHashing Using Deep Pyramidal Residual Learning

Image dehashing refers to the process of inferring images by inverting image hashes. Recently, image dehashing from real-valued image retrieval hashes is shown feasible using deep convolutional neural networks. However, the perceptual quality of dehashed images is challenged when real-valued hashes are quantized to less bits. Besides, the scalability to larger or color image dehashing is limited in the previous dehashing network. To this end, we propose a pyramidal long-range residual-learning network (PyLRR-Net). PyLRR-Net is a pyramidal image reconstruction network to dehash images in a progressive manner. At each image scale, we design and insert a long-range residual block to refine the coarse image reconstruction leveraging deep residual learning. Experiments on both grayscale and color image datasets show that the proposed PyLRR-Net outperforms previous work in terms of image dehashing quality, scalability, and flexibility for large and color image dehashing problems.