Table of Contents
Advertisement
The dots in this screening technique are usually smaller than those in
AM screening and they are arranged in a seemingly random pattern.
This method provides better reproduction of finely detailed and
continuous-tone images. Because this technique does not lay the dots
on grids, it eliminates rosette and moiré patterns on printed images.
Error diffusion algorithms use data from surrounding cells to place
dots. The difference between the gray level or color tone requested
and that printed for a cell is fed through an error filter and carried by
the program to other cells, as they are processed, "diffusing" the
error across surrounding cells. XANTÉ provides three error diffusion
algorithms, Diffuse 1, 2, and 3, selectable from either the front
panel's PRINT:SCREEN menu or from the PPD's Screen Type
options.
Diffuse 1 is the error diffusion algorithm introduced by Floyd and
Steinberg. This algorithm reproduces midtone gray levels well, but
creates some artifacts (repetitive patterns) and sharpens the image.
Diffuse 2 is the "Minimum Average Error" algorithm presented by
Jarvis, Judice, and Ninke. This uses the Floyd and Steinberg process,
but with a different error filter. While artifacts are decreased in
images processed with this method, the directional presentation of
the error is more obvious, and the sharpening of lines in the image is
increased.
Diffuse 3 uses the Stucki Filter. The images tend to be similar to
those produced by Jarvis, et al., but Stucki added an additional filter
to control the sharpening of lines in the image.
For a detailed discussion of the error diffusion algorithms, see R.
Ulichney's Digital Halftoning (Cambridge, MIT Press, 1987).
XANTÉ Scaling
The XANTÉ Scaling feature is designed to override the limitation of
applications to produce large printed pages when scanned images
are used, such as TIFF or eps files. (Plain line drawings with
scalable fonts can be scaled up as large as you wish without
pixilation.)
_______________________________________ Imaging Basics 7-13
Advertisement
Table of Contents
Troubleshooting
