US Patent 7373011 Density-dependent sharpening

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.