A computer dismantles a two-dimensional initial image into partial images
containing components that vary locally with partial image frequencies
and a residual image containing a direct component which is locally
invariable. For each partial image and residual image the computer
determines a weighting factor and sums the weighted images into a final
image. Based on a comparison of the partial image frequencies with a
target frequency, the computer determines a partial image as a pilot
image and its frequency as a pilot frequency. The computer determines
weighting factors of the partial images so that partial images whose
frequencies are below the pilot frequency are weighted less than the
pilot image, and partial images whose frequencies are above the pilot
frequency makes a large contribution when the noise component in the
initial image is small and a small contribution when the noise component
in the initial image is large.