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基于灵活稀疏结构控制和自适应优化算法的模糊图像盲复原

Blind Image Deblurring via Adaptive Optimization with Flexible Sparse Structure Control

  • 摘要: 模糊图像的盲复原是一个长期存在的病态逆问题。为了从模糊观测中恢复出清晰图像,目前已有的工作基于最大后验估计设计了很多针对清晰图像的先验以缩小解空间,而过于复杂的非凸先验会造成最终模型优化困难。同时,在现实场景下,由于未知的图像分布,复杂的模糊过程以及不均匀的图像噪声,很难显式地设计出一个固定先验适应于所有情况。因此我们采用了自适应优化的思想,在优化过程中对图像稀疏结构进行控制。在本篇文章中,我们提出了不带有任何先验项的轻量级模型,结合投影梯度法在优化过程中加入了图像稀疏结构控制模块。此外,我们训练了一组卷积神经网络从不同噪声下的训练数据中学习清晰图像的稀疏结构。相比之前以lp范数控制图像稀疏结构的启发式过程,避免了人工调参的繁琐。实验证明基于卷积神经网络的稀疏结构控制结果与lp范数相近,但对图像噪声更为鲁棒。在合成数据集以及真实图像上的实验结果表明,我们提出的方法可以有效应用到不同场景下,且相比目前较新方法有明显优势。

     

    Abstract: Blind image deblurring is a long-standing ill-posed inverse problem which aims to recover a latent sharp image given only a blurry observation. So far, existing studies have designed many effective priors w.r.t. the latent image within the maximum a posteriori (MAP) framework in order to narrow down the solution space. These non-convex priors are always integrated into the final deblurring model, which makes the optimization challenging. However, due to unknown image distribution, complex kernel structure and non-uniform noises in real-world scenarios, it is indeed challenging to explicitly design a fixed prior for all cases. Thus we adopt the idea of adaptive optimization and propose the sparse structure control (SSC) for the latent image during the optimization process. In this paper, we only formulate the necessary optimization constraints in a lightweight MAP model with no priors. Then we develop an inexact projected gradient scheme to incorporate flexible SSC in MAP inference. Besides lp-norm based SSC in our previous work, we also train a group of denoising convolutional neural networks (CNNs) to learn the sparse image structure automatically from the training data under different noise levels, and we show that CNNs-based SSC can achieve similar results compared with lp-norm but are more robust to noise. Extensive experiments demonstrate that the proposed adaptive optimization scheme with two types of SSC achieves the state-of-the-art results on both synthetic data and real-world images.

     

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