  Raster images can have a range of various distortions connected to their
raster structure. Upsampling them might in effect substantially yield the
raster structure of the original image, known as aliasing. The upsampling
itself may introduce aliasing into the upsampled image as well. The presented
method attempts to remove the aliasing using frequency filters based on the
discrete fast Fourier transform, and applied directionally in certain regions
placed along the edges in the image.
  As opposed to some anisotropic smoothing methods, the presented algorithm
aims to selectively reduce only the aliasing, preserving the sharpness of image
details.
  The method can be used as a post--processing filter along with various
upsampling algorithms. It was experimentally shown that the method can improve
the visual quality of the upsampled images.
