Abstract—Effective image-fusion methods inject the necessary geometric information and preserve the radiometric information. To preserve the radiometric information, the injected high frequency of a panchromatic (pan) image must follow the frequency of the multispectral (MS) image. In this letter,< Final Year Projects > an improved additive-wavelet (AW) fusion method is presented using the à trous algorithm. The proposed method does not decompose the MS image; thus, it preserves the radiometric information of the MS image and can inject high frequency following the frequency of the MS image using a low-resolution pan image. Experimental results obtained using IKONOS data indicate that the proposed method produces superior-quality images compared with the AW luminance proportional method in a quantitative analysis.