Spectral preservation of pan-sharpening for THEOS imagery

Image fusion in remote sensing is usually called pan-sharpening, which is a useful method to synthesis a high resolution multispectral image (MS) from the combining of a high resolution panchromatic image (PAN) with a low resolution MS image. The popular fusion methods are intensity-hue-saturation (IHS)-based methods. However, the IHS-based methods have two major problems: (i) out-of-gamut due to transformation between red-green-blue (RGB) and IHS color systems and (ii) color distortion due to variation of saturation and intensity in image fusion. The proposed method studied on the relationship between intensity and saturation to preserve spectral information of the fusing THEOS images. Thus, we found a suitable color space, iHSL (improved hue-saturation-lightness) for pan-sharpening that can isolate the intensity or lightness component. The fusion method employs smooth filter-based intensity modulation technique to merge the spatial information from PAN with the intensity component from MS images. From the studied results, our method could preserve the spectral information better than the well-known IHS-based methods.