The detail in an image can be enhanced by selective filtering to separate
at least one part of the frequency spectrum of the image from a remaining
part of the image. The amplitude of the separated part of the frequency
spectrum of image is changed and the amplitude-changed portion is
combined with the remaining part of the image. The filtering and/or the
change in amplitude is controlled at least in part in response to the
content of the image to enhance the detail level of the image where
appropriate, while preventing enhancement in areas of the picture where
it is likely that artifacts would be generated.