Infrared small target detection (IRSTD) has been widely applied and developed in military and civilian fields, playing a vital role. Despite the extensive research foundation of traditional manual feature-based methods, they are still constrained by the inherent problem of infrared small targets lacking prior features. In recent years, the advancement of deep learning methods has enriched the research landscape in this field, yet they are still constrained by the imbalance of positive and negative samples between the target and the background. To address these issues, we propose a novel prior guided dense nested network (PGDN-Net), which ingeniously integrates traditional manual features with a deep learning network model. First, three prior features are extracted, including the high-order Riesz transform feature, the compactness and heterogeneity feature (CH), and the corner feature of the structure tensor (ST). Then, these features are input into a dense nested network for guidance, supported by a two-orientation attention aggregation module and a channel and spatial attention module. Different features play their respective guiding roles in different depths of the network. Through multiple attention mechanisms and feature fusion operations on the interested target area, the extraction and preservation of target features can be improved, while easily removing irrelevant backgrounds. Experiments on public datasets demonstrate the effectiveness and progressiveness of our PGDN-Net. Compared with other state-of-the-art methods, it achieves better performance in background suppression, target enhancement, probability of detection, and false alarm rate. In addition, the PGDN-Net model can effectively maintain and restore the original shape of the target while performing robust detection, which is beneficial for subsequent fine-grained recognition tasks.

SAR-assisted thick cloud removal from optical remote sensing images has long been a challenging task. Current mainstream methods face challenges in achieving an effective global receptive field, fully utilizing multi-scale features, and deeply integrating features from both modalities. To overcome these limitations, we propose the Multi-scale Multi-branch Mamba model(M3-CR) for SAR-assisted thick cloud removal. Specifically, we integrate the Mamba model into the task of SAR-assisted cloud removal, effectively modeling global dependencies within the images. Concurrently, a Multi-scale Multi-branch structure is introduced to extract and integrate multi-scale information, and in combination with a convolutional branch to fully exploit the global and local geographic proximities inherent in remote sensing images. Furthermore, we present a novel feature fusion module leveraging the Modal-Traversing 2D Selective Scan(MTSS2D) to enable deep interaction and integration of features from optical and SAR images. The experimental results on two benchmark databases show that the M3-CR achieves superior performance compared to state-of-theart cloud removal approaches, while requiring fewer parameters and reduced FLOPs. The code for M3-CR will be made publicly available at https://github.com/LinpengPan/M3CR.

Abstract—Remote sensing (RS) images are widely used for Earth observation. However, cloud contamination greatly degrades the quality of RS images and limits their applications. In this letter, we propose a coarse-to-fine thick cloud removal method for a single pair of multitemporal RS images. First, we perform a global color transformation on a cloud-free reference image using linear regression coefficients between the pixels in the cloudy target image and the reference image in the same cloud-free regions, and obtain a coarse result. Then, a convolutional neural network (CNN) based on internal constraint is used to refine the coarse result, which does not require any construction of additional external training dataset in advance. We further design a multiscale feature extraction and fusion module and an auxiliary loss involving cloud regions to improve the performance of the CNN. Finally, Poisson image fusion is employed to generate a seamless cloud-free result. On a simulated test set containing 500 pairs of multitemporal RS images, the proposed method achieves satisfactory results with 25.1277 dB in peak signal-to-noise ratio (PSNR), 0.9077 in structural similarity (SSIM), and 0.9342 in correlation coefficient (CC). Qualitative and quantitative comparisons of our proposed against several state-of-the-art methods on the simulated and real cloudy images demonstrate the superiority of the proposed method.

Stitched remote sensing images often exhibit irregular boundaries, which can be frustrating for general users and detrimental to downstream tasks such as object detection and segmentation. However, this issue has received insufficient attention and remains unexplored within the remote sensing domain. In this study, we investigate mesh-based rectangling techniques for remote sensing images, aiming to produce rectangular outputs while preserving the original field-of-view (FoV) and avoiding the introduction of unreliable content. Observing that prior rectangling algorithms tend to generate unsatisfactory boundaries or discernible distortions, that is, under-rectangling or over-rectangling, we propose the concept of a warping kernel associated with mesh deformations to account for these phenomena. Consequently, we introduce the iterative warping kernel self-correction transformer (IWKFormer), designed to enhance warping kernel estimation and generate superior rectangular outcomes. It primarily comprises two components: a mesh feature extractor built upon the partial swin transformer block (PSTB) and a corrector module using the swin transformer block (STB). These modules collaborate to derive warping kernels implicitly. The extractor extracts latent features pertinent to mesh deformation, whereas the corrector iteratively refines the warping kernel estimation to improve the ultimate prediction. Furthermore, to bolster further research, we have constructed an aerial imagery stitching rectangling dataset (AIRD), featuring a wide array of stitching scenes. Extensive experimentation on the AIRD demonstrates that our method yields visually appealing and naturally rectangled images, achieving state-of-the-art performance. The code and data will be available athttps://github.com/yyywxk/IWKFormer.

The thin cloud removal (CR) technique has great practical value for the application of remote sensing images. Existing deep-learning-based methods have attained remarkable achievements. However, most of them neglect the inherent feature correlations in deeper layers due to learning in a successive manner. In this letter, we propose a compact thin cloud removal network based on the feedback (FB) mechanism, called CRFB-Net, which leverages the high-level features as feedback information to modulate shallow representations. CRFB-Net employs the recurrent architecture to achieve such a feedback scheme. Specifically, the restoration process does not terminate after obtaining an output. In this case, the output of intermediate iterations will flow into the next iteration as feedback. For better utilization of feedback, a multiscale feature fusion block (MFFB) is designed to refine the low-level representations from three scales. Furthermore, we introduce a curriculum learning strategy to train the CRFB-Net by gradually increasing the complexity of restoration, through which a sharper result is produced step by step. Extensive experiments demonstrate the superiority of our CRFB-Net, outperforming state-of-the-art.

Thin cloud removal from remote sensing (RS) images is challenging. Recently, deep-learning-based methods have achieved excellent results using supervised training on paired image data. However, in practice, real paired image data are unavailable. Therefore, in this letter, we propose a novel thin cloud removal method, a physical-model-based CycleGAN (PM-CycleGAN), which can be trained using only unpaired data. The PM-CycleGAN training process comprises forward and backward loops. The forward loop first decomposes a cloudy image into a cloud-free image, thin cloud thickness map, and thickness coefficient using three generators. Then, it combines these three components using a physical model to reconstruct the original cloudy image to obtain the cycle consistency constraint. The backward loop first uses the physical model to synthesize a cloud-free image, thin cloud thickness map, and thickness coefficient into a cloudy image, which are then decomposed into the original three components using the three generators. Visual and quantitative comparisons against several state-of-the-art (SOTA) methods on a cloudy image dataset demonstrated the superiority of PM-CycleGAN.