Face Super-Resolution (FSR), aiming to improve the quality of Low-Resolution (LR) facial images, has been greatly propelled by the deep learning techniques. However, existing approaches, whether based on Convolutional Neural Networks (CNNs) or Transformers, are either inherently damaging facial structures limited by their architectures or failing to capture essential multi-scale textures due to the rigid receptive fields. To address these concerns, we propose a novel dual-domain feature interaction method called Spatial-frequency Multi-scale feature Learning Network (SMLNet) for FSR by employing a dual-branch architecture. Specifically, the frequency branch captures high-quality global structures and fine high-frequency details, while the spatial branch operates complementarily to preserve fine-grained local texture patterns. Moreover, we further introduce a Multi-scale Spatial-frequency feature Interaction Module (MSIM), which combines a Multi-scale Feature Extraction Block (MFEB) and a Spatial-Frequency feature Interaction Module (SFIM) to interact and aggregate multi-level complementary features from the dual branches. Extensive quantitative experiments and qualitative analyses across multiple datasets, together with evaluations on real-world images, demonstrate that the proposed SMLNet significantly outperforms other state-of-the-art methods.

Abstract Accurate detection of algae in microscopic image plays a crucial role in water quality monitoring. However, the existing object detection methods still face challenges in accurately detecting different categories of algae in microscopic image. In order to improve the accuracy, an improved YOLOv5s model is proposed for microalgae detection, by combining a Receptive Field Enhancement (RFE) module, the Wise‐IoU v3 dynamic non‐monotonic focal loss function, and a Dynamic head (Dyhead), which is termed receptive field enhancement wise‐IoU dyhead (RWD)‐you only look once (YOLO). Firstly, to detect microalgae of various scales, the Bottleneck in the C3 module of YOLOv5s is replaced with a more reasonable RFE module. Secondly, Wise‐IoU v3 is applied to enhance detection accuracy by assigning varying weights between high‐quality and low‐quality images. Finally, Dyhead is introduced to enhance the representation capacity of the detection head by integrating three attention mechanisms: scale awareness, spatial awareness, and task awareness. The proposed RWD‐YOLO model significantly enhances the accuracy of algae detection in microscopic image. Specifically, the experimental results on the microalgae dataset show that the RWD‐YOLO achieves an [email protected] of 93.2% and an [email protected]:0.95 of 65.1%. Compared to the original YOLOv5s, [email protected] and [email protected]:0.95 are improved by 3.7% and 5.7%, respectively.

Broad learning system (BLS), an efficient neural network with a flat structure, has received a lot of attention due to its advantages in training speed and network extensibility. However, the conventional BLS adopts the least square loss, which treats each sample equally and thus is sensitivity to noise and outliers. To address this concern, in this article we propose a self-paced BLS (SPBLS) model by incorporating the novel self-paced learning (SPL) strategy into the network for noisy data regression. With the assistance of the SPL criterion, the model output is used as feedback to learn appropriate priority weight to readjust the importance of each sample. Such a reweighting strategy can help SPBLS to distinguish samples from "easy" to "difficult" in model training, equipping the model robust to noise and outliers while maintaining the characteristics of the original system. Moreover, two incremental learning algorithms associated to SPBLS have also been developed, with which the system can be updated quickly and flexibly without retraining the entire model when new training samples are added or the network needs to be expanded. Experiments conducted on various datasets demonstrate that the proposed SPBLS can achieve satisfying performance for noisy data regression.

Multi-shot coded aperture snapshot spectral imaging (CASSI) uses multiple measurement snapshots to encode the three-dimensional hyperspectral image (HSI). Increasing the number of snapshots will multiply the number of measurements, making CASSI system more appropriate for detailed spatial or spectrally rich scenes. However, the reconstruction algorithms still face the challenge of being ineffective or inflexible. In this paper, we propose a plug-and-play (PnP) method that uses denoiser as priors for multi-shot CASSI. Specifically, the proposed PnP method is based on the primal-dual algorithm with linesearch (PDAL), which makes it flexible and can be used for any multi-shot CASSI mechanisms. Furthermore, a new subspaced-based nonlocal reweighted low-rank (SNRL) denoiser is presented to utilize the global spectral correlation and nonlocal self-similarity priors of HSI. By integrating the SNRL denoiser into PnP-PDAL, we show the balloons ( 512×512×31 ) in CAVE dataset recovered from two snapshots compressive measurements with MPSNR above 50 dB. Experimental results demonstrate that our proposed method leads to significant improvements compared to the current state-of-the-art methods.

Hyperspectral images (HSIs) are inevitably contaminated by the mixed noise (such as Gaussian noise, impulse noise, deadlines, and stripes), which could influence the subsequent processing accuracy. Generally, HSI restoration can be transformed into the low-rank matrix recovery (LRMR). In the LRMR, the nuclear norm is widely used to substitute the matrix rank, but its effectiveness is still worth improving. Besides, the$l_{0}$-norm cannot capture the sparse noise’s structured sparsity property. To handle these issues, the adaptive rank and structured sparsity corrections (ARSSC) are presented for HSI restoration. The ARSSC introduces two convex regularizers, that is: 1) the rank correction (RC) and 2) the structured sparsity correction (SSC), to, respectively, approximate the matrix rank and the$l_{2,0}$-norm. The RC and the SSC can adaptively offset the penalization of large entries from the nuclear norm and the$l_{2,1}$-norm, respectively, where the larger the entry, the greater its offset. Therefore, the proposed ARSSC achieves a tighter approximation of the noise-free HSI low-rank structure and promotes the structured sparsity of sparse noise. An efficient alternative direction method of multipliers (ADMM) algorithm is applied to solve the resulting convex optimization problem. The superiority of the ARSSC in terms of the mixed noise removal and spatial-spectral structure information preserving, is demonstrated by several experimental results both on simulated and real datasets, compared with other state-of-the-art HSI restoration approaches.

Hyperspectral images (HSIs) are often degraded by a mixture of various types of noise during the imaging process, including Gaussian noise, impulse noise, and stripes. Such complex noise could plague the subsequent HSIs processing. Generally, most HSI denoising methods formulate sparsity optimization problems with convex norm constraints, which over-penalize large entries of vectors, and may result in a biased solution. In this paper, a nonconvex regularized low-rank and sparse matrix decomposition (NonRLRS) method is proposed for HSI denoising, which can simultaneously remove the Gaussian noise, impulse noise, dead lines, and stripes. The NonRLRS aims to decompose the degraded HSI, expressed in a matrix form, into low-rank and sparse components with a robust formulation. To enhance the sparsity in both the intrinsic low-rank structure and the sparse corruptions, a novel nonconvex regularizer named as normalized ε -penalty, is presented, which can adaptively shrink each entry. In addition, an effective algorithm based on the majorization minimization (MM) is developed to solve the resulting nonconvex optimization problem. Specifically, the MM algorithm first substitutes the nonconvex objective function with the surrogate upper-bound in each iteration, and then minimizes the constructed surrogate function, which enables the nonconvex problem to be solved in the framework of reweighted technique. Experimental results on both simulated and real data demonstrate the effectiveness of the proposed method.

Hyperspectral compressive sensing (HCS) is considered for reconstructing the hyperspectral image (HSI) from a few random sampled measurements. HCS is crucial for the onboard imaging systems to cut down the acquisition time and data storage volume, and simultaneously maintain image quality. In this paper, a spatial-spectral total variation (SSTV) regularized low-rank tensor decomposition (LRTD) method is proposed for HCS. Specifically, for the HSI, the tensor nuclear norm based LRTD is utilized to characterize the global correlation among all bands, and an anisotropic SSTV regularization is explored to describe the local spatial smooth structure and spectral correlation of adjacent bands. In addition, an efficient algorithm based on the alternative direction multiplier method is developed to solve the resulting optimization problem. Experimental results demonstrate that the proposed method is superior to the existing state-of-the-art ones.

Tensor completion (TC), aiming to recover original high-order data from its degraded observations, has recently drawn much attention in hyperspectral images (HSIs) domain. Generally, the widely used TC methods formulate the rank minimization problem with a convex trace norm penalty, which shrinks all singular values equally, and may generate a much biased solution. Besides, these TC methods assume the whole high-order data is of low-rank, which may fail to recover the detail information in high-order data with diverse and complex structures. In this paper, a novel nonlocal low-rank regularization-based TC (NLRR-TC) method is proposed for HSIs, which includes two main steps. In the first step, an initial completion result is generated by the proposed low-rank regularization-based TC (LRR-TC) model, which combines the logarithm of the determinant with the tensor trace norm. This model can more effectively approximate the tensor rank, since the logarithm function values can be adaptively tuned for each input. In the second step, the nonlocal spatial-spectral similarity is integrated into the LRR-TC model, to obtain the final completion result. Specifically, the initial completion result is first divided into groups of nonlocal similar cubes (each group forms a 3-D tensor), and then the LRR-TC is applied to each group. Since similar cubes within each group contain similar structures, each 3-D tensor should have low-rank property, and thus further improves the completion result. Experimental results demonstrate that the proposed NLRR-TC method outperforms state-of-the-art HSIs completion techniques.

Recently, robust principal component analysis (RPCA) based methods have been used for hyperspectral images (HSIs) restoration to simultaneously remove several types of noise, including Gaussian noise, impulse noise, stripes, and so on. However, most of these RPCA methods formulate the optimization problem with a convex l1-norm penalty, which over-penalizes large entries of vectors, and results in a biased solution. In this paper, a novel nonconvex sparsity regularizer (NonSR) for measuring the clean HSI low rank structure and noise sparsity structure is proposed, which can effectively approximate rank function and noise sparsity instead of the convex l1-norm. By embedding the sparsity regularizer into the RPCA framework, we formulate a new model, which enhance the capability in simultaneously removing several types of noise. In addition, an iterative algorithm based on the alternative direction multiplier method (ADMM) is developed to effectively solve the proposed model. Experimental results demonstrate that the proposed NonSR method outperforms state-of-the-art HSIs restoration techniques.