A method, system, and software are disclosed for improving the quality of
a signal. A base signal is recursively decomposed for a desired number of
pyramid levels. The decomposed signal from the lowest level is modified
to generate a preprocessed signal. The preprocessed signal from the
lowest level is used to improve signal components or characteristics of
the decomposed signal of the next higher level of the pyramidal
decomposition, resulting in a modified signal at the next higher level.
In one embodiment, the preprocessed signal includes filter mask that is
used to guide a filtering process on the decomposed signal of the next
higher level. In another embodiment, the preprocessed signal includes a
up-predicted signal that is combined with the decomposed signal of the
next higher level. The preprocessed signal from a lower level is used to
generate a modified signal at a higher level. The generation of a
preprocessed signal and a modified signal is recursively repeated for
each level until the highest level of the pyramidal decomposition is
reached, resulting in an improved base signal. The present invention
finds particular application in photography and digital film processing,
whereby the illustrated method may be used to reduce image noise, thereby
improving image quality.