[hylafax-users] [ps->tiffg3 in ghostscript] Dithering

[David Hsu <David.Hsu@anstat.com.au>]

Hi All,

This question may be more for the ghostscript community however given the
focus is on the tiffg3(2d) device I thought I'll get more luck here (and
besides I'm using hylafax).  I'm using ghostscript 6.50-02 and I'm trying to
stop/reduce the dithering on outgoing (monochrome) image faxes.  Currently
if I try to send using -l, the images are dithered and there's a grid-like
pattern of dots.  If I try using -m, the grid is finer and looks ok however
it takes a long time to send (like 4 minutes/page).  I'm trying to
reduce/eliminate this grid pattern.

Reading ps2tiff it seems the following parameters are passed to gs:

-q -dNOPAUSE -dBATCH -dSAFER -sPAPERSIZE=a4 -dFIXEDMEDIA -r204x98
-sDEVICE=tiffg3 (or tiffg32d)

* I've tried using different TIFF devices (all with -r204x98) and none
worked. :-(

* I also tried gs' dithering algorithm by using the bmp16 and bmp256 devices
and the bmp16 outputs the same problem image.  bmp256 looks ok though. :-(  

* I've then tried to change the dithering by (this is a guess)
-sDithering=(gsmono|fsmono|gscmyk|gsrgb|fs2|fsrgb|hscmyk|fscmyk) and none
seem to affect anything. :-(

Any ideas appreciated.  Thanks.

David Hsu
Anstat Property Group                       mailto:davidh@anstat.com.au
224-226 Normanby Road, Southbank 3006       tel:+61 3 92781174
Victoria, Australia                         fax:+61 3 92781167



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