Fusion of multispectral and panchromatic images using improved IHS and PCA mergers based on wavelet decomposition

TLDR

Since Chavez introduced a high‑pass filtering approach for fusing multispectral and panchromatic images, many methods have been devised to extract spatial detail from the panchromatic image and inject it into the multispectral one. This study proposes new fusion alternatives that employ multiresolution wavelet decomposition for detail extraction and then use intensity‑hue‑saturation (IHS) and principal component analysis (PCA) to merge the extracted detail into the multispectral image. The authors applied both decimated and undecimated wavelet decompositions, merged the images using IHS and PCA, compared the resulting products spectrally and spatially, and evaluated them visually and quantitatively on SPOT 4 XI and M images at a 4:1 ratio. The proposed methods yield higher‑quality fused images than standard IHS, PCA, and wavelet techniques, with the undecimated wavelet decomposition delivering the best results.

Abstract

Since Chavez proposed the highpass filtering procedure to fuse multispectral and panchromatic images, several fusion methods have been developed based on the same principle: to extract from the panchromatic image spatial detail information to later inject it into the multispectral one. In this paper, we present new fusion alternatives based on the same concept, using the multiresolution wavelet decomposition to execute the detail extraction phase and the intensity-hue-saturation (IHS) and principal component analysis (PCA) procedures to inject the spatial detail of the panchromatic image into the multispectral one. The multiresolution wavelet decomposition has been performed using both decimated and undecimated algorithms and the resulting merged images compared both spectral and spatially. These fusion methods, as well as standard IHS-, PCA-, and wavelet-based methods have been used to merge Systeme Pour l'Observation de la Terre (SPOT) 4 XI and SPOT 4 M images with a ratio 4:1. We have estimated the validity of each fusion method by analyzing, visually and quantitatively, the quality of the resulting fused images. The methodological approaches proposed in this paper result in merged images with improved quality with respect to those obtained by standard IHS, PCA, and standard wavelet-based fusion methods. For both proposed fusion methods, better results are obtained when an undecimated algorithm is used to perform the multiresolution wavelet decomposition.