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Image demoireing is a multi-faceted image restoration task involving both moire pattern removal and color restoration. In this paper, we raise a general degradation model to describe an image contaminated by moire patterns, and propose a novel multi-scale bandpass convolutional neural network (MBCNN) for single image demoireing. For moire pattern removal, we propose a multi-block-size learnable bandpass filters (M-LBFs), based on a block-wise frequency domain transform, to learn the frequency domain priors of moire patterns. We also introduce a new loss function named Dilated Advanced Sobel loss (D-ASL) to better sense the frequency information. For color restoration, we propose a two-step tone mapping strategy, which first applies a global tone mapping to correct for a global color shift, and then performs local fine tuning of the color per pixel. To determine the most appropriate frequency domain transform, we investigate several transforms including DCT, DFT, DWT, learnable non-linear transform and learnable orthogonal transform. We finally adopt the DCT. Our basic model won the AIM2019 demoireing challenge. Experimental results on three public datasets show that our method outperforms state-of-the-art methods by a large margin. [ABSTRACT FROM AUTHOR]

The dense connection is a powerful technique to build wider and deeper convolution neural networks (CNNs) for handling several computer vision tasks. Despite the excellent performance, it consumes numerous parameters and produces a large weight model file. We studied the distribution of convolution layers and proposed a hard parameter sharing approach known as convolution pool (CP) for compressing dense-connection-based image restoration CNN models. CP is used to reallocate the parameters to specific convolution layers to ensure that some can be shared in different layers. We design a set of dense-connection-based baselines for three typical image restoration tasks, including image denoising, super-resolution, and JPEG deblocking, to validate the performance of the proposed method. Moreover, we comprehensively analyze the potential problems by introducing CP, including group convolution, dilated convolution, and modeling efficiency. Experimental results demonstrate that the proposed method can efficiently achieve an impressive compression rate with negligible performance reduction. [ABSTRACT FROM AUTHOR]

Re-ranking is becoming a critical part of retrieved based Person re-identification algorithms. Existing re-ranking methods always require lots of queries and memory to go through the k -nearest neighbors. To solve this problem, we introduce a Feature Relation Map (FRM) to mine the latent relation between the k -neighbors through convolution neural network, and propose a metric learning based Similarity Evaluation (SE) model to obtain the re-ranking distance from the FRM. The dilated convolution is then introduced by concatenating the dilated convolution kernels and normal convolution kernels along the channel dimension in the improvement of the SE model (named SE-d model), to allow the SE model to efficiently compare more samples pairs for obtaining the final re-ranking distance. Further, we embedding out FRM-SE model to the existing re-ranking methods to prove the effectiveness of our re-ranking model. The experiments on Market1501, CUHK03, DukeMTMC and MSMT17 benchmarks illustrates the superiority of proposed method to the state-of-the-art re-ranking methods. Although the SE model make a great improve performance, the SE-d model gains an increase of 0.31%, 0.63% in top-1 respectably compared with the SE model in the DukeMTMC and MSMT17 datasets. Meanwhile, the SE-d model speed up the model convergence and shorten the training time. Furthermore, in the transfer learning setting, the model trained on either Market1501, CUHK03 or DukeMTMC can achieve a comparable accuracy improvement on the MSMT17 dataset, which validates the generalization of our SE model. [ABSTRACT FROM AUTHOR]