[sane-devel] Descreening Utility For SANE

Frank Peters frank.peters at comcast.net
Sat Jul 29 22:52:03 UTC 2006


Hello,

For any list members that are interested in making high-quality
scans of halftone material from books and publications, I will
now report on a free utility that may be of great use.

High resolution scans (600 dpi) of material that was originally
printed with the halftone process will generally preserve the 
annoying and distracting halftone pattern.  Some scanners may
offer a "descreening" option to ameliorate this pattern, but most
do not.  The SANE software also has no descreening provisions.

One alternative would be to load a scanned image into the
GIMP and then employ the fourier plug-in to remove the low
frequency spatial components.  Although this method can give
excellent results,  its use is cumbersome and very time consuming
as each image must be processed manually.  What is needed is
an automatic approach.

After some Internet searching, I did discover an automatic
tool that will effectively eliminate the halftone pattern
from high resolution scans.  The source code, which is free
and without restrictions, is available here:

http://www.picturel.com/halftone/

In conjunction with the SANE package, this utility can produce
very fine results.

However, there are a few limitations.  The code is relatively old
(ca. 1998), and can handle only 8-bit images.  Also, the utility
is meant for grayscale images only.  (Because of the nature of
color halftoning, decomposing an image into its red, green, and
blue channels, followed by descreening and recombining,  will
give poor results.)  However, if these limitations are not that
important to you, then by all means you should give this utility
a try.

The code compiles on 32-bit Linux.  (It will compile on x86_64
but will not execute successfully.  It apparently is not 64-bit
clean.)

Perhaps the SANE developers would like to give this code an
evaluation for possible inclusion into SANE.

Regards,

Frank Peters
Detroit, Michigan
USA



More information about the sane-devel mailing list