The paper proposes a new rule of image fusion.We start with taking local Fourier Transform of high frequency sub-images in image fusion based on the pyramid and Wavelet Transform

get their harmonious energy

then consider the ratio of these energy and the energy of the corresponding area in the low frequency image as the rule of pixels choice.We apply the rule in multi-focus image fusion and multi-band remote sensing image fusion and conclude that the efficient fusion rule is better than current principle in some fields.