Abstract: With the rapid development of remote sensing technology,more and more satellites can simultaneously acquire both panchromatic (PAN) and multispectral (MS) imagery．In general,spatial resolution of the MS imagery is relatively lower than that of PAN imagery．However,MS imagery with high spatial resolution is more desirable in application． Although various image fusion algorithms have been developed to pansharpen MS imagery,there are still some problems regarding spectral and spatial distortion．In addition,due to large size of remote sensing imagery product,running times of existing fusion methods are hard to match user’s expectation．To solve these problems,a high fidelity fusion method based on ratio transform was proposed to fuse PAN and MS imagery．In this method,a degraded image is generated by down-sampling and up-sampling of PAN image,while a MS image is up-sampled by bilinear interpolation．Then,fused image is obtained by multiplying the up-sampled to a ratio between the PAN image and its degraded version．Experimental results show that the proposed method has better spatial and spectral fidelity performance than compared methods.

Key words: Image fusion,Pansharpening,Image enhancement,Ratio transform