Unleashing Fourier-Domain Potential: Spatial–Spectral Reconstruction Framework for Remote Sensing Pansharpening

Pansharpening aims to generate high-resolution multispectral (HR-MS) images by fusing the corresponding low-resolution multispectral (LR-MS) and high-resolution panchromatic (PAN) images. While the spatial-spectral properties modeling plays crucial roles in generating high-quality HR-MS images, existing approaches suffer from: 1) directly modeling the entangled spatial-spectral properties; and 2) lacking task-specific priors for spatial and spectral properties modeling. This paper proposes a novel Fourier domain-based approach (Fourier-SSR) to address these problems, where phase and amplitude components of PAN and LR-MS are considered to individually model spatial and spectral properties for the target HR-MS image. Our Fourier-SSR is motivated by the crucial findings in Fourier domain: (i) manifestation of spatial-spectral properties, i.e., the spatial and spectral properties of remote sensing images can be individually manifested in their phase and amplitude components in Fourier domain; (ii) spatial property-related prior, i.e., only reconstructing the phase component of PAN image in Fourier domain, could generate spatial property required for target HR-MS image; and (iii) spectral property-related prior, i.e., jointly models the amplitude components of PAN and LR-MS images could generate the required spectral property for target HR-MS image. Based on the aforementioned findings, we design a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Fourier-guided spatial Mixer</i> and a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Fourier-guided spectral Mixer</i>, which innovatively employ complex feature interaction strategies to individually reconstruct the phase and amplitude components for target HR-MS. Experiments show that our methods unleash Fourier domain potential in individually modeling spatial and spectral properties for the target HR-MS image, leading to superior performance over previous state-of-the-art. Our code is provided in Supplementary Material.