A sharpening filter is disclosed for performing density-dependent
sharpening on digital images. In one embodiment, a digital image to be
sharpened is decomposed into a plurality of high-pass versions of the
image at different resolutions. These high-pass images are gained at each
resolution and recombined with the original image to produce a sharpened
version of the image. The gains that are applied at each resolution are
density-dependent. As a result, the effects of density-dependent blurring
are counteracted, such that the sharpness of the final printed image is
independent of the print density. Techniques are disclosed for performing
such density-dependent sharpening with a high degree of computational
efficiency.