This book includes various simulations on medical image database and natural image database. In this book author has nicely simulated various image fusion rules on basic to advance frequency domain. Author has selected five image data-set from large medical and natural database for simulation using various image fusion rules. This book mainly focuses on Averaging, Maximum Selection and PCA fusion rule in DWT, Contourlet transform and Ripplet transform. In the spatial domain, fusion rule is reforming with direct pixel value which is sensitive to human eyes. While in the frequency domain decomposition is done in various bands and due to that it over comes the problem of directly dealing with the pixel value. Hence frequency domain works better compare to the spatial domain. In this book simulation results show that DWT has poor directionality that can be improved with Contourlet transform. But Ripplet transform is having advance property like anisotropy, directionality and good localization so it gives more informative results for image fusion.