论文标题

可解释的双层优化:赫尔辛基DeBlur挑战的应用

Explainable bilevel optimization: an application to the Helsinki deblur challenge

论文作者

Bonettini, Silvia, Franchini, Giorgia, Pezzi, Danilo, Prato, Marco

论文摘要

在本文中,我们提出了一种用于解决一般图像去除问题问题的双光线优化方案,其中一种类似变量的方法封装在机器学习方案中,以提供具有自动学习参数的高质量重建图像。赫尔辛基·迪布尔挑战2021专门选择了较低级别和机器学习上层的成分,其中要求字母序列从越来越多的模糊水平中从异常照片中恢复。我们针对重建图像的提议的程序包括固定数量的Fista迭代,用于最小化边缘保留和二进制,从而强制实施正则最小二乘功能。定义变分模型和优化步骤的参数(与大多数深度学习方法不同,都具有精确且可解释的含义,都是通过相似性索引或支持向量机策略来学习的。挑战作者提供的测试图像上的数值实验表明,与标准变异方法和性能相比,与一些提出的基于深度学习的算法相当的性能,这些算法需要优化数百万个参数。

In this paper we present a bilevel optimization scheme for the solution of a general image deblurring problem, in which a parametric variational-like approach is encapsulated within a machine learning scheme to provide a high quality reconstructed image with automatically learned parameters. The ingredients of the variational lower level and the machine learning upper one are specifically chosen for the Helsinki Deblur Challenge 2021, in which sequences of letters are asked to be recovered from out-of-focus photographs with increasing levels of blur. Our proposed procedure for the reconstructed image consists in a fixed number of FISTA iterations applied to the minimization of an edge preserving and binarization enforcing regularized least-squares functional. The parameters defining the variational model and the optimization steps, which, unlike most deep learning approaches, all have a precise and interpretable meaning, are learned via either a similarity index or a support vector machine strategy. Numerical experiments on the test images provided by the challenge authors show significant gains with respect to a standard variational approach and performances comparable with those of some of the proposed deep learning based algorithms which require the optimization of millions of parameters.

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