A method for decomposing a digital image at resolution R and MR into a set
of spatial sub-bands of resolution R and MR where MR>R and where the
high-band at resolution MR is calculated by subtracting the filtered and
up-sampled image at resolution R from the image at resolution MR and
where the spatial low-band at resolution R is calculated by adding the
filtered and down-sampled spatial high-band to the image at resolution R
and where a rational factor for up-and down-sampling M is determined by
the resolution ratio.