61 research outputs found
Guided Nonlocal Patch Regularization and Efficient Filtering-Based Inversion for Multiband Fusion
In multiband fusion, an image with a high spatial and low spectral resolution
is combined with an image with a low spatial but high spectral resolution to
produce a single multiband image having high spatial and spectral resolutions.
This comes up in remote sensing applications such as pansharpening~(MS+PAN),
hyperspectral sharpening~(HS+PAN), and HS-MS fusion~(HS+MS). Remote sensing
images are textured and have repetitive structures. Motivated by nonlocal
patch-based methods for image restoration, we propose a convex regularizer that
(i) takes into account long-distance correlations, (ii) penalizes patch
variation, which is more effective than pixel variation for capturing texture
information, and (iii) uses the higher spatial resolution image as a guide
image for weight computation. We come up with an efficient ADMM algorithm for
optimizing the regularizer along with a standard least-squares loss function
derived from the imaging model. The novelty of our algorithm is that by
expressing patch variation as filtering operations and by judiciously splitting
the original variables and introducing latent variables, we are able to solve
the ADMM subproblems efficiently using FFT-based convolution and
soft-thresholding. As far as the reconstruction quality is concerned, our
method is shown to outperform state-of-the-art variational and deep learning
techniques.Comment: Accepted in IEEE Transactions on Computational Imagin
Generative Adversarial Network for Pansharpening With Spectral and Spatial Discriminators
The pansharpening problem amounts to fusing a high-resolution panchromatic image with a low-resolution multispectral image so as to obtain a high-resolution multispectral image. Therefore, the preservation of the spatial resolution of the panchromatic image and the spectral resolution of the multispectral image is of key importance for the pansharpening problem. To cope with it, we propose a new method based on a bidiscriminator in a generative adversarial network (GAN) framework. The first discriminator is optimized to preserve textures of images by taking as input the luminance and the near-infrared band of images, and the second discriminator preserves the color by comparing the chroma components Cb and Cr. Thus, this method allows to train two discriminators, each one with a different and complementary task. Moreover, to enhance these aspects, the proposed method based on bidiscriminator, and called MDSSC-GAN SAM, considers a spatial and a spectral constraint in the loss function of the generator. We show the advantages of this new method on experiments carried out on Pléiades and World View 3 satellite images.Super-résolution d'images multi-échelles en sciences des matériaux avec des attributs géométrique
Robust Hyperspectral Image Fusion with Simultaneous Guide Image Denoising via Constrained Convex Optimization
The paper proposes a new high spatial resolution hyperspectral (HR-HS) image
estimation method based on convex optimization. The method assumes a low
spatial resolution HS (LR-HS) image and a guide image as observations, where
both observations are contaminated by noise. Our method simultaneously
estimates an HR-HS image and a noiseless guide image, so the method can utilize
spatial information in a guide image even if it is contaminated by heavy noise.
The proposed estimation problem adopts hybrid spatio-spectral total variation
as regularization and evaluates the edge similarity between HR-HS and guide
images to effectively use apriori knowledge on an HR-HS image and spatial
detail information in a guide image. To efficiently solve the problem, we apply
a primal-dual splitting method. Experiments demonstrate the performance of our
method and the advantage over several existing methods.Comment: Accepted to IEEE Transactions on Geoscience and Remote Sensin
AN IMPROVED VARIATIONAL METHOD FOR HYPERSPECTRAL IMAGE PANSHARPENING WITH THE CONSTRAINT OF SPECTRAL DIFFERENCE MINIMIZATION
Variational pansharpening can enhance the spatial resolution of a hyperspectral (HS) image using a high-resolution panchromatic (PAN) image. However, this technology may lead to spectral distortion that obviously affect the accuracy of data analysis. In this article, we propose an improved variational method for HS image pansharpening with the constraint of spectral difference minimization. We extend the energy function of the classic variational pansharpening method by adding a new spectral fidelity term. This fidelity term is designed following the definition of spectral angle mapper, which means that for every pixel, the spectral difference value of any two bands in the HS image is in equal proportion to that of the two corresponding bands in the pansharpened image. Gradient descent method is adopted to find the optimal solution of the modified energy function, and the pansharpened image can be reconstructed. Experimental results demonstrate that the constraint of spectral difference minimization is able to preserve the original spectral information well in HS images, and reduce the spectral distortion effectively. Compared to original variational method, our method performs better in both visual and quantitative evaluation, and achieves a good trade-off between spatial and spectral information
Pansharpening via Frequency-Aware Fusion Network with Explicit Similarity Constraints
The process of fusing a high spatial resolution (HR) panchromatic (PAN) image
and a low spatial resolution (LR) multispectral (MS) image to obtain an HRMS
image is known as pansharpening. With the development of convolutional neural
networks, the performance of pansharpening methods has been improved, however,
the blurry effects and the spectral distortion still exist in their fusion
results due to the insufficiency in details learning and the frequency mismatch
between MSand PAN. Therefore, the improvement of spatial details at the premise
of reducing spectral distortion is still a challenge. In this paper, we propose
a frequency-aware fusion network (FAFNet) together with a novel high-frequency
feature similarity loss to address above mentioned problems. FAFNet is mainly
composed of two kinds of blocks, where the frequency aware blocks aim to
extract features in the frequency domain with the help of discrete wavelet
transform (DWT) layers, and the frequency fusion blocks reconstruct and
transform the features from frequency domain to spatial domain with the
assistance of inverse DWT (IDWT) layers. Finally, the fusion results are
obtained through a convolutional block. In order to learn the correspondence,
we also propose a high-frequency feature similarity loss to constrain the HF
features derived from PAN and MS branches, so that HF features of PAN can
reasonably be used to supplement that of MS. Experimental results on three
datasets at both reduced- and full-resolution demonstrate the superiority of
the proposed method compared with several state-of-the-art pansharpening
models.Comment: 14 page
Panchromatic and multispectral image fusion for remote sensing and earth observation: Concepts, taxonomy, literature review, evaluation methodologies and challenges ahead
Panchromatic and multispectral image fusion, termed pan-sharpening, is to merge the spatial and spectral information of the source images into a fused one, which has a higher spatial and spectral resolution and is more reliable for downstream tasks compared with any of the source images. It has been widely applied to image interpretation and pre-processing of various applications. A large number of methods have been proposed to achieve better fusion results by considering the spatial and spectral relationships among panchromatic and multispectral images. In recent years, the fast development of artificial intelligence (AI) and deep learning (DL) has significantly enhanced the development of pan-sharpening techniques. However, this field lacks a comprehensive overview of recent advances boosted by the rise of AI and DL. This paper provides a comprehensive review of a variety of pan-sharpening methods that adopt four different paradigms, i.e., component substitution, multiresolution analysis, degradation model, and deep neural networks. As an important aspect of pan-sharpening, the evaluation of the fused image is also outlined to present various assessment methods in terms of reduced-resolution and full-resolution quality measurement. Then, we conclude this paper by discussing the existing limitations, difficulties, and challenges of pan-sharpening techniques, datasets, and quality assessment. In addition, the survey summarizes the development trends in these areas, which provide useful methodological practices for researchers and professionals. Finally, the developments in pan-sharpening are summarized in the conclusion part. The aim of the survey is to serve as a referential starting point for newcomers and a common point of agreement around the research directions to be followed in this exciting area
Panchromatic and multispectral image fusion for remote sensing and earth observation: Concepts, taxonomy, literature review, evaluation methodologies and challenges ahead
Panchromatic and multispectral image fusion, termed pan-sharpening, is to merge the spatial and spectral information of the source images into a fused one, which has a higher spatial and spectral resolution and is more reliable for downstream tasks compared with any of the source images. It has been widely applied to image interpretation and pre-processing of various applications. A large number of methods have been proposed to achieve better fusion results by considering the spatial and spectral relationships among panchromatic and multispectral images. In recent years, the fast development of artificial intelligence (AI) and deep learning (DL) has significantly enhanced the development of pan-sharpening techniques. However, this field lacks a comprehensive overview of recent advances boosted by the rise of AI and DL. This paper provides a comprehensive review of a variety of pan-sharpening methods that adopt four different paradigms, i.e., component substitution, multiresolution analysis, degradation model, and deep neural networks. As an important aspect of pan-sharpening, the evaluation of the fused image is also outlined to present various assessment methods in terms of reduced-resolution and full-resolution quality measurement. Then, we conclude this paper by discussing the existing limitations, difficulties, and challenges of pan-sharpening techniques, datasets, and quality assessment. In addition, the survey summarizes the development trends in these areas, which provide useful methodological practices for researchers and professionals. Finally, the developments in pan-sharpening are summarized in the conclusion part. The aim of the survey is to serve as a referential starting point for newcomers and a common point of agreement around the research directions to be followed in this exciting area
A Benchmarking Protocol for SAR Colorization: From Regression to Deep Learning Approaches
Synthetic aperture radar (SAR) images are widely used in remote sensing.
Interpreting SAR images can be challenging due to their intrinsic speckle noise
and grayscale nature. To address this issue, SAR colorization has emerged as a
research direction to colorize gray scale SAR images while preserving the
original spatial information and radiometric information. However, this
research field is still in its early stages, and many limitations can be
highlighted. In this paper, we propose a full research line for supervised
learning-based approaches to SAR colorization. Our approach includes a protocol
for generating synthetic color SAR images, several baselines, and an effective
method based on the conditional generative adversarial network (cGAN) for SAR
colorization. We also propose numerical assessment metrics for the problem at
hand. To our knowledge, this is the first attempt to propose a research line
for SAR colorization that includes a protocol, a benchmark, and a complete
performance evaluation. Our extensive tests demonstrate the effectiveness of
our proposed cGAN-based network for SAR colorization. The code will be made
publicly available.Comment: 16 pages, 16 figures, 6 table
Advantages of nonlinear intensity components for contrast-based multispectral pansharpening
In this study, we investigate whether a nonlinear intensity component can be beneficial for multispectral (MS) pansharpening based on component-substitution (CS). In classical CS methods, the intensity component is a linear combination of the spectral components and lies on a hyperplane in the vector space that contains the MS pixel values. Starting from the hyperspherical color space (HCS) fusion technique, we devise a novel method, in which the intensity component lies on a hyper-ellipsoidal surface instead of on a hyperspherical surface. The proposed method is insensitive to the format of the data, either floating-point spectral radiance values or fixed-point packed digital numbers (DNs), thanks to the use of a multivariate linear regression between the squares of the interpolated MS bands and the squared lowpass filtered Pan. The regression of squared MS, instead of the Euclidean radius used by HCS, makes the intensity component no longer lie on a hypersphere in the vector space of the MS samples, but on a hyperellipsoid. Furthermore, before the fusion is accomplished, the interpolated MS bands are corrected for atmospheric haze, in order to build a multiplicative injection model with approximately de-hazed components. Experiments on GeoEye-1 and WorldView-3 images show consistent advantages over the baseline HCS and a performance slightly superior to those of some of the most advanced methodsPeer ReviewedPostprint (published version
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