As the quality of optical sensors improves, there is a need for processing large-scale images. In particular, the ability of devices to capture ultra-high definition (UHD) images and video places new demands on the image processing pipeline. In this paper, we consider the task of low-light image enhancement (LLIE) and introduce a large-scale database consisting of images at 4K and 8K resolution. We conduct systematic benchmarking studies and provide a comparison of current LLIE algorithms. As a second contribution, we introduce LLFormer, a transformer-based low-light enhancement method. The core components of LLFormer are the axis-based multi-head self-attention and cross-layer attention fusion block, which significantly reduces the linear complexity. Extensive experiments on the new dataset and existing public datasets show that LLFormer outperforms state-of-the-art methods. We also show that employing existing LLIE methods trained on our benchmark as a pre-processing step significantly improves the performance of downstream tasks, e.g., face detection in low-light conditions. The source code and pre-trained models are available at https://github.com/TaoWangzj/LLFormer.

Image restoration under hazy weather condition, which is called single image dehazing, has been of significant interest for various computer vision applications. In recent years, deep learning-based methods have achieved success. However, existing image dehazing methods typically neglect the hierarchy of features in the neural network and fail to exploit their relationships fully. To this end, we propose an effective image dehazing method named Hierarchical Contrastive Dehazing (HCD), which is based on feature fusion and contrastive learning strategies. HCD consists of a hierarchical dehazing network (HDN) and a novel hierarchical contrastive loss (HCL). Specifically, the core design in the HDN is a Hierarchical Interaction Module, which utilizes multi-scale activation to revise the feature responses hierarchically. To cooperate with the training of HDN, we propose HCL which performs contrastive learning on hierarchically paired exemplars, facilitating haze removal. Extensive experiments on public datasets, RESIDE, HazeRD, and DENSE-HAZE, demonstrate that HCD quantitatively outperforms the state-of-the-art methods in terms of PSNR, SSIM and achieves better visual quality.

Face Restoration (FR) aims to restore High-Quality (HQ) faces from Low-Quality (LQ) input images, which is a domain-specific image restoration problem in the low-level computer vision area. The early face restoration methods mainly use statistic priors and degradation models, which are difficult to meet the requirements of real-world applications in practice. In recent years, face restoration has witnessed great progress after stepping into the deep learning era. However, there are few works to study deep learning-based face restoration methods systematically. Thus, this paper comprehensively surveys recent advances in deep learning techniques for face restoration. Specifically, we first summarize different problem formulations and analyze the characteristic of the face image. Second, we discuss the challenges of face restoration. Concerning these challenges, we present a comprehensive review of existing FR methods, including prior based methods and deep learning-based methods. Then, we explore developed techniques in the task of FR covering network architectures, loss functions, and benchmark datasets. We also conduct a systematic benchmark evaluation on representative methods. Finally, we discuss future directions, including network designs, metrics, benchmark datasets, applications,etc. We also provide an open-source repository for all the discussed methods, which is available at https://github.com/TaoWangzj/Awesome-Face-Restoration.

由于缺乏异常样品，因此仅具有正常样本的先验知识的异常检测才吸引更多的注意力。现有的基于CNN的像素重建方法遇到了两个问题。首先，重建源和目标是包含无法区分的语义信息的原始像素值。其次，CNN倾向于很好地重建正常样品和异常情况，使它们仍然很难区分。在本文中，我们提出异常检测变压器（ADTR）将变压器应用于重建预训练的特征。预训练的功能包含可区分的语义信息。同样，采用变压器限制以很好地重构异常，因此一旦重建失败，就可以轻松检测到异常。此外，我们提出了新的损失函数，使我们的方法与正常样本的情况以及具有图像级和像素级标记为异常的异常情况兼容。通过添加简单的合成或外部无关异常，可以进一步提高性能。广泛的实验是在包括MVTEC-AD和CIFAR-10在内的异常检测数据集上进行的。与所有基线相比，我们的方法取得了卓越的性能。

盲人面部修复（BFR）旨在从低品质的图像中恢复高质量的面部图像，并通常求助于面部先验，以改善恢复性能。但是，当前的方法仍然遇到两个主要困难：1）如何在不进行大规模调整的情况下得出强大的网络体系结构； 2）如何从一个网络中的多个面部先验捕获互补信息以提高恢复性能。为此，我们提出了一个面部修复搜索网络（FRSNET），以适应我们指定的搜索空间内的合适特征提取体系结构，这可以直接有助于恢复质量。在FRSNET的基础上，我们通过多个学习方案进一步设计了多个面部先验搜索网络（MFPSNET）。 MFPSNET最佳地从不同的面部先验中提取信息，并将信息融合到图像特征中，以确保保留外部指导和内部特征。通过这种方式，MFPSNet充分利用了语义级别（解析图），几何级别（面部热图），参考级别（面部词典）和像素级（降级图像）信息，从而产生忠实且逼真的图像。定量和定性实验表明，MFPSNET在合成和现实世界数据集上对最先进的BFR方法表现出色。这些代码可公开可用：https：//github.com/yyj1ang/mfpsnet。

盲面修复（BFR）旨在从相应的低质量（LQ）输入中构建高质量（HQ）面部图像。最近，已经提出了许多BFR方法，并取得了杰出的成功。但是，这些方法经过私人合成的数据集进行了培训或评估，这使得与后续方法相比的方法是不可行的。为了解决这个问题，我们首先合成两个称为EDFEACE-CELEB-1M（BFR128）和EDFACE-CELEB-150K（BFR512）的盲面恢复基准数据集。在五个设置下，将最先进的方法在它们的五个设置下进行了基准测试，包括模糊，噪声，低分辨率，JPEG压缩伪像及其组合（完全退化）。为了使比较更全面，应用了五个广泛使用的定量指标和两个任务驱动的指标，包括平均面部标志距离（AFLD）和平均面部ID余弦相似性（AFICS）。此外，我们开发了一个有效的基线模型，称为Swin Transformer U-NET（昏迷）。带有U-NET体系结构的昏迷器应用了注意机制和移动的窗口方案，以捕获远程像素相互作用，并更多地关注重要功能，同时仍受到有效训练。实验结果表明，所提出的基线方法对各种BFR任务的SOTA方法表现出色。

这项工作研究了很少的对象计数的问题，该问题计算了查询图像中出现的示例对象的数量（即由一个或几个支持图像描述）。主要的挑战在于，目标对象可以密集地包装在查询图像中，从而使每个单一对象都很难识别。为了解决障碍，我们提出了一个新颖的学习块，配备了相似性比较模块和功能增强模块。具体来说，给定支持图像和查询图像，我们首先通过比较每个空间位置的投影特征来得出分数图。有关所有支持图像的得分图将共收集在一起，并在示例维度和空间维度上均标准化，从而产生可靠的相似性图。然后，我们通过使用开发的点相似性作为加权系数来增强使用支持功能的查询功能。这样的设计鼓励模型通过更多地关注类似于支持图像的区域来检查查询图像，从而导致不同对象之间的界限更加清晰。在各种基准和培训设置上进行了广泛的实验表明，我们通过足够大的边距超过了最先进的方法。例如，在最近的大规模FSC-147数据集中，我们通过将平均绝对误差从22.08提高到14.32（35％$ \ uparrow $）来超越最新方法。代码已在https://github.com/zhiyuanyou/safecount中发布。

模糊文物可以严重降低图像的视觉质量，并且已经提出了许多用于特定场景的脱模方法。然而，在大多数现实世界的图像中，模糊是由不同因素引起的，例如运动和散焦。在本文中，我们解决了不同的去纹身方法如何在一般类型的模糊上进行。对于深入的性能评估，我们构建一个名为（MC-Blur）的新型大规模的多个原因图像去孔数据集，包括现实世界和合成模糊图像，具有模糊的混合因素。采用不同的技术收集所提出的MC-Blur数据集中的图像：卷积超高清（UHD）具有大核的锐利图像，平均由1000 FPS高速摄像头捕获的清晰图像，向图像添加Defocus，而且真实-world模糊的图像由各种相机型号捕获。这些结果概述了当前的去纹理方法的优缺点。此外，我们提出了一种新的基线模型，适应多种模糊的原因。通过包括对不同程度的特征的不同重量，所提出的网络导出更强大的特征，重量分配给更重要的水平，从而增强了特征表示。新数据集上的广泛实验结果展示了多原因模糊情景所提出的模型的有效性。

最近的深面幻觉方法显示出令人惊叹的超级分辨面部图像，甚至超过人类能力。但是，这些算法主要在非公共合成数据集上评估。因此，尚不清楚这些算法如何在公共面幻觉数据集上执行。同时，大多数现有数据集都不太考虑种族的分布，这使得在这些数据集上训练的面部幻觉方法偏向于某些特定种族。为了解决上述两个问题，在本文中，我们构建了一个公共种族多样化的面部数据集，Edface-Celeb-1M，并设计了面部幻觉的基准任务。我们的数据集包括170万张覆盖不同国家 /地区的照片，并具有平衡的种族组成。据我们所知，它是野外最大且公开的面部幻觉数据集。与该数据集相关联，本文还贡献了各种评估协议，并提供了全面的分析，以基于现有的最新方法。基准评估证明了最新算法的性能和局限性。

Weakly-supervised object localization aims to indicate the category as well as the scope of an object in an image given only the image-level labels. Most of the existing works are based on Class Activation Mapping (CAM) and endeavor to enlarge the discriminative area inside the activation map to perceive the whole object, yet ignore the co-occurrence confounder of the object and context (e.g., fish and water), which makes the model inspection hard to distinguish object boundaries. Besides, the use of CAM also brings a dilemma problem that the classification and localization always suffer from a performance gap and can not reach their highest accuracy simultaneously. In this paper, we propose a casual knowledge distillation method, dubbed KD-CI-CAM, to address these two under-explored issues in one go. More specifically, we tackle the co-occurrence context confounder problem via causal intervention (CI), which explores the causalities among image features, contexts, and categories to eliminate the biased object-context entanglement in the class activation maps. Based on the de-biased object feature, we additionally propose a multi-teacher causal distillation framework to balance the absorption of classification knowledge and localization knowledge during model training. Extensive experiments on several benchmarks demonstrate the effectiveness of KD-CI-CAM in learning clear object boundaries from confounding contexts and addressing the dilemma problem between classification and localization performance.