Blurry video frame interpolation (BVFI), which aims to generate high-frame-rate clear videos from low-frame-rate blurry inputs, is a challenging yet significant task in computer vision. Current state-of-the-art approaches typically rely on linear or quadratic models to estimate intermediate motion. However, these methods often overlook depth variations that occur during fast object motion, leading to changes in object size and hindering interpolation performance.This paper proposes the Differential Curves-guided Blurry Video Frame Interpolation (DC-BVFI) framework, which leverages the differential curves theory to analyze and mitigate the effects of depth variations caused by object motion. Specifically, DC-BVFI consists of UBNet and MPNet. Unlike prior approaches that rely on optical flow for frame interpolation, MPNet is designed to estimate the 3D scene flow, which facilitates a more precise awareness of depth and velocity variations. Since scene flow cannot be directly inferred in the 2D frame space, UBNet is introduced to transform them into 3D point maps. Extensive experiments demonstrate that the proposed DC-BVFI framework surpasses state-of-the-art performance in simulated and real-world datasets.

There are two main methods that can be used to accelerate MRI reconstruction: parallel imaging and compressed sensing. To further accelerate the sampling process, the combination of these two methods has been extensively studied in recent years. However, existing MRI reconstruction methods often overlook the exploration of high-frequency information of images, leading to sub-optimal recovery of fine details in the reconstructed results. To address this issue, we conduct an in-depth analysis of image gradients and propose a novel MRI reconstruction model based on Maximum a Posteriori (MAP) estimation. We first establish the Cumulative Deviation from Maximum Gradient magnitude (CDMG) prior for fully sampled MR images through theoretical analysis, then incorporate this explicit CDMG prior along with an implicit deep prior to form the prior probability term. This combination of priors strikes a balance between physically informed constraints and data-driven adaptability, aiding in the recovery of meaningful high-frequency information. Additionally, we introduce a multi-order gradient operator to enhance the observation model, thereby improving the accuracy of the likelihood term. Through MAP estimation, we develop a novel accelerated MRI reconstruction model, the optimization of which is achieved by unrolling it into a convolutional neural network structure, referred to as DDGU-Net. Extensive experimental results demonstrate the effectiveness of our approach in reconstructing high-quality MR images and achieving state-of-the-art (SOTA) results, particularly at higher acceleration factors.

Homography estimation is essential for aligning images captured from different viewpoints by accurately modeling the geometric relationship between them. In homography estimation, global information plays a critical role. To establish global correspondences, cross-attention has been widely used in recent studies. However, vanilla cross-attention mechanisms treat queries in redundant and low-texture areas the same as those in richly textured areas, leading to the accumulation and propagation of erroneous information. We define this phenomenon, where the model excessively attends to queries in redundant and low-texture areas, as query over-focusing. To alleviate query over-focusing and achieve fine-grained homography estimation, we propose a novel homography estimation network, termed AGNet, which integrates an Adaptive Query Transformer (AQFormer) and a Gated Interaction Module (GIM). The AQFormer is designed to dynamically adjust attention by applying a mask to queries, allowing the model to adaptively emphasize feature-rich regions while suppressing redundant or weakly textured areas. Meanwhile, the GIM selectively captures local information by adjusting convolutional kernels based on input, enhancing the extraction of shared features between image pairs. Extensive experiments on various datasets demonstrate that AGNet significantly improves accuracy in homography estimation, particularly in challenging scenarios with low overlap and large viewpoint variations.

The process of fusing low-resolution multispectral (LRMS) and high-resolution panchromatic (PAN) imagery, commonly referred to as pansharpening, is intended to generate high-resolution multispectral (HRMS) imagery. Typically, most pre-existing pansharpening frameworks mainly emphasize the straightforward learning of the mapping relationship among PAN and LRMS images to HRMS images. However, a key limitation of these frameworks is their potential overemphasis on spatial information, particularly the enhancement of low-frequency components. As a result, such an oversight potentially hinders the model's ability to simultaneously restore both spectral and spatial details. To address this issue, we propose a novel pansharpening model based on the denoising diffusion probabilistic model (DDPM), dubbed FrDiff. Specifically, we build a framelet-based conditional diffusion model that leverages the generative power of diffusion models to produce more refine results. Different from conventional methods directly inferring HRMS images, our strategy is designed to project their framelet coefficients, utilizing the available PAN and LRMS images as resources. This approach enables the separation of high-frequency and low-frequency components through framelet transformation, which are subsequently recombined to create a novel set of conditional embeddings that feed into the diffusion process. At the same time, the powerful predictive power of the diffusion model is exploited to simultaneously recover the high-frequency and low-frequency components of the HRMS. Moreover, we introduce a framelet-oriented cross-attention module dedicated to honing spectral fidelity. This module is crucial for improving the spectral precision of the HRMS images, ensuring a balanced emphasis on both spatial and spectral enhancements. Quantitative and qualitative experiments on multiple benchmark datasets demonstrate that the proposed method achieves more robustness and high-quality results than other state-of-the-art pansharpening methods.

Blurry video frame interpolation (BVFI) aims to generate high-frame-rate clear videos from low-frame-rate blurry videos, is a challenging but important topic in the computer vision community. Blurry videos not only provide spatial and temporal information like clear videos, but also contain additional motion information hidden in each blurry frame. However, existing BVFI methods usually fail to fully leverage all valuable information, which ultimately hinders their performance. In this paper, we propose a simple three-stage temporal deformable network to fully explore useful information from blurry videos. The frame interpolation stage designs a deformable network to directly sample useful information from blurry inputs and synthesize an intermediate frame at an arbitrary time interval. The temporal feature fusion stage explores the long-term temporal information for each target frame through a bi-directional recurrent deformable alignment network. And the deblurring stage applies a transformer-empowered Taylor approximation network to recursively recover the high-frequency details. Quantitative and qualitative results indicate that our model outperforms existing SOTA methods.

With the increasing significance of high-quality, high-resolution multispectral images (HRMS) in various domains, pansharpening, which fuses low-resolution multispectral images (LRMS) with high-resolution panchromatic images (PAN), has gained considerable attention. However, current deep learning methods have limitations in capturing global long-range dependencies and incorporating spectral characteristics across different spectral bands of multispectral images (MS). Additionally, model-based approaches do not effectively utilize the multi-scale information between LRMS and HRMS data, limiting their further performance enhancement. To address these limitations, we propose a new observation model based on Multi-Scale Convolutional Sparse Coding (MS-CSC) and design a novel Multi-Scale Hybrid Spatial-spectral Transformer (MSHST) for the unfolding networks. The MS-CSC based observation model aims to fuse multi-scale information, while the MSHST incorporates spatial self-attention to capture global long-range dependencies and spectral self-attention to capture the inter-band correlation. Experimental results demonstrate the superiority of our method over other state-of-the-art approaches in both reduced-resolution and full-resolution evaluations. Ablation experiments further validate the effectiveness of the proposed multi-scale model and MSHST. Code is available at https://github.com/Eternityyx/MSCSCformer.

Pansharpening aims to sharpen low resolution (LR) multispectral (MS) images with the help of corresponding high resolution (HR) panchromatic (PAN) images to obtain HRMS images. Model-based pansharpening methods manually design objective functions via observation model and hand-crafted priors. However, inevitable performance degradation may occur in the case that the prior is invalid. Although many deep learning based end-to-end pansharpening methods have been proposed recently, they still need to be improved due to the insufficient study on HRMS related domain knowledge. Besides, existing pansharpening methods rarely consider the misalignments between MS and PAN images, leading to poor performance. To tackle these issues, this paper proposes to unrolling the observation model with registration embedding for pansharpening. Inspired by the optical flow estimation, we embed the registration operation into the observation model to reconstruct the pansharpening function with the help of a deep prior of HRMS images, and then unroll the iterative solution into a novel deep convolutional network.. Apart from the single HRMS supervision, we also introduce a consistency loss to supervise the two degradation processes. The use of consistency loss enables the degradation sub-networks to learn more realistic degradation. Experimental results at reduced-resolution and full-resolution are reported to demonstrate the superiority of the proposed method to other state-of-the-art pansharpening methods. In GaoFen-2 dataset evaluation, our method achieves 1.2dB higher PSNR than SOTA techniques.

Most modern satellites can provide two types of images: 1) panchromatic (PAN) image and 2) multispectral (MS) image. The former has high spatial resolution and low spectral resolution, while the latter has high spectral resolution and low spatial resolution. To obtain images with both high spectral and spatial resolution, pansharpening has emerged to fuse the spatial information of the PAN image and the spectral information of the MS image. However, most pansharpening methods fail to preserve spatial and spectral information simultaneously. In this article, we propose a framelet-based convolutional neural network (CNN) for pansharpening which makes it possible to pursue both high spectral and high spatial resolution. Our network consists of three subnetworks: 1) feature embedding net; 2) feature fusion net; and 3) framelet prediction net. Different from conventional CNN methods directly inferring high-resolution MS images, our approach learns to predict their framelet coefficients from available PAN and MS images. The introduction of multilevel feature aggregation and hybrid residual connection makes full use of spatial information of PAN image and spectral information of MS image. Quantitative and qualitative experiments at reduced- and full-resolution demonstrate that the proposed method achieves more appealing results than other state-of-the-art pansharpening methods. The source code and trained models are available at https://github.com/TingMAC/FrMLNet.

Pansharpening aims to produce a high-resolution multispectral (HRMS) image by combining a low-resolution multispectral (LRMS) image with a high-resolution panchromatic (PAN) image through a fusion process. Deep learning (DL)-based pansharpening methods have demonstrated impressive results in generating high-quality HRMS images. However, they suffer from a lack of interpretability due to their black-box network architectures. Recently, model-based deep unrolling networks have been proposed to improve the interpretability of networks. Among these approaches, the multi-source convolutional sparse coding (MCSC)-based models stand out by effectively learning common and unique features from both LRMS and PAN images, showing promising results. As the LRMS image provides limited information in MCSC-based models, it can result in weak feature response and even lead to incorrect fusion outcomes. To address this issue, we propose a novel deep MCSC-based method that enhances the robustness and performance. Specifically, we build an optimization model that integrates MCSC with a degradation model and a deep prior, which can sufficiently capture the common information shared by the latent HRMS images and PAN images, thereby enabling the recovery of more accurate spectral information. To optimize the proposed model, we adopt an iterative optimization strategy that unfolds the iterative solution into networks. Moreover, we propose an enhanced version of our method that utilizes multi-scale dictionaries to capture common and unique features at different scales, thereby facilitating the extraction of more abundant spectral and spatial details. We evaluate the effectiveness of our proposed method on multiple benchmark datasets. Experiment results demonstrate its effectiveness in improving the robustness and performance of MCSC-based models.

It has been demonstrated that the blurring process reduces the high-frequency information of the original sharp image, so the main challenge for image deblurring is to reconstruct high-frequency information from the blurry image. In this paper, we propose a novel image deblurring framework to focus on the reconstruction of high-frequency information, which consists of two main subnetworks: a high-frequency reconstruction subnetwork (HFRSN) and a multi-scale grid subnetwork (MSGSN). The HFRSN is built to reconstruct latent high-frequency information from multiple scale blurry images. The MSGSN performs deblurring processes with high-frequency guidance at different scales simultaneously. Besides, in order to better use high-frequency information to restore sharpening images, we designed a high-frequency information aggregation (HFAG) module and a high-frequency information attention (HFAT) module in MSGSN. The HFAG module is designed to fuse high-frequency features and image features at the feature extraction stage, and the HFAT module is built to enhance the feature reconstruction stage. Extensive experiments on different datasets show the effectiveness and efficiency of our method.

Exemplar-based colorization aims to add colors to a grayscale image guided by a content related reference image. Existing methods are either sensitive to the selection of reference images (content, position) or extremely time and resource consuming, which limits their practical application. To tackle these problems, we propose a deep exemplar colorization architecture inspired by the characteristics of stylization in feature extracting and blending. Our coarse- to-fine architecture consists of two parts: a fast transfer sub-net and a robust colorization sub-net. The transfer sub- net obtains a coarse chrominance map via matching basic feature statistics of the input pairs in a progressive way. The colorization sub-net refines the map to generate the final results. The proposed end-to-end network can jointly learn faithful colorization with a related reference and plausible color prediction with unrelated reference. Extensive experimental validation demonstrates that our approach outperforms the state-of-the-art methods in less time whether in exemplar-based colorization or image stylization tasks.

In this paper, we investigate the challenging task of removing haze from a single natural image. The analysis on the haze formation model shows that the atmospheric veil has much less relevance to chrominance than luminance, which motivates us to neglect the haze in the chrominance channel and concentrate on the luminance channel in the dehazing process. Besides, the experimental study illustrates that the YUV color space is most suitable for image dehazing. Accordingly, a variational model is proposed in the Y channel of the YUV color space by combining the reformulation of the haze model and the two effective priors. As we mainly focus on the Y channel, most of the chrominance information of the image is preserved after dehazing. The numerical procedure based on the alternating direction method of multipliers (ADMM) scheme is presented to obtain the optimal solution. Extensive experimental results on real-world hazy images and synthetic dataset demonstrate clearly that our method can unveil the details and recover vivid color information, which is competitive among many existing dehazing algorithms. Further experiments show that our model also can be applied for image enhancement.

Image colorization refers to a computer-assisted process that adds colors to grayscale images. It is a challenging task since there is usually no one-to-one correspondence between color and local texture. In this paper, we tackle this issue by exploiting weighted nonlocal self-similarity and local consistency constraints at the resolution of superpixels. Given a grayscale target image, we first select a color source image containing similar segments to target image and extract multi-level features of each superpixel in both images after superpixel segmentation. Then a set of color candidates for each target superpixel is selected by adopting a top-down feature matching scheme with confidence assignment. Finally, we propose a variational approach to determine the most appropriate color for each target superpixel from color candidates. Experiments demonstrate the effectiveness of the proposed method and show its superiority to other state-of-the-art methods. Furthermore, our method can be easily extended to color transfer between two color images.

Blind image deblurring aims to recover sharp image from a blurred one while the blur kernel is unknown. To solve this ill-posed problem, a great amount of image priors have been explored and employed in this area. In this paper, we present a blind deblurring method based on Local Maximum Gradient (LMG) prior. Our work is inspired by the simple and intuitive observation that the maximum value of a local patch gradient will diminish after the blur process, which is proved to be true both mathematically and empirically. This inherent property of blur process helps us to establish a new energy function. By introducing an liner operator to compute the Local Maximum Gradient, together with an effective optimization scheme, our method can handle various specific scenarios. Extensive experimental results illustrate that our method is able to achieve favorable performance against state-of-the-art algorithms on both synthetic and real-world images.

In this letter, we propose a fast and robust method for stitching overlapped images captured by the unmanned aerial vehicle. First, we apply the shape-preserving half-projective method to precisely and stably align a pair of partially overlapped input images. Then, an optimal stitching line is searched to remove ghosts caused by the moving objects in the overlapped area. We subsequently propose a color blending method to eliminate all the color inconsistencies in the prealigned image. In accordance with the color differences of the pixels on the optimal stitching seam, we utilize weighted value coordinate interpolation algorithms to compute accurate color changes for all the pixels in the target image. The calculated color changes are then added to the target image to remove the color inconsistency. Furthermore, we introduce the superpixel segmentation to divide the target image into a reduced number of superpixels, and we assign each superpixel the same color change value. Such a superpixel level operation can greatly reduce the computational complexity. Experiments show that our method is promising to achieve effective and efficient stitching results.

Pansharpening is a process of acquiring a multi-spectral image with high spatial resolution by fusing a low resolution multi-spectral image with a corresponding high resolution panchromatic image. In this paper, a new pansharpening method based on the Bayesian theory is proposed. The algorithm is mainly based on three assumptions: 1) the geometric information contained in the pan-sharpened image is coincident with that contained in the panchromatic image; 2) the pan-sharpened image and the original multi-spectral image should share the same spectral information; and 3) in each pan-sharpened image channel, the neighboring pixels not around the edges are similar. We build our posterior probability model according to above-mentioned assumptions and solve it by the alternating direction method of multipliers. The experiments at reduced and full resolution show that the proposed method outperforms the other state-of-the-art pansharpening methods. Besides, we verify that the new algorithm is effective in preserving spectral and spatial information with high reliability. Further experiments also show that the proposed method can be successfully extended to hyper-spectral image fusion.