An important scenario for image quality assessment (IQA) is to evaluate image
restoration (IR) algorithms. The state-of-the-art approaches adopt a
full-reference paradigm that compares restored images with their corresponding
pristine-quality images. However, pristine-quality images are usually
unavailable in blind image restoration tasks and real-world scenarios. In this
paper, we propose a practical solution named degraded-reference IQA (DR-IQA),
which exploits the inputs of IR models, degraded images, as references.
Specifically, we extract reference information from degraded images by
distilling knowledge from pristine-quality images. The distillation is achieved
through learning a reference space, where various degraded images are
encouraged to share the same feature statistics with pristine-quality images.
And the reference space is optimized to capture deep image priors that are
useful for quality assessment. Note that pristine-quality images are only used
during training. Our work provides a powerful and differentiable metric for
blind IRs, especially for GAN-based methods. Extensive experiments show that
our results can even be close to the performance of full-reference settings.

本文介绍了一种命名为 DR-IQA 的实用解决方案，利用失真图像作为参考，通过学习参考空间来提取参考信息并捕获有用于质量评估的深度图像先验，从而为盲目的图像恢复任务提供强大的可微指标，同时在 GAN-based 方法中表现良好。