[Desktop_printing] Smooth dithering

Kai-Uwe Behrmann ku.b at gmx.de
Thu Feb 16 23:23:56 PST 2006


preparing a comparision between a standard prepress RIP and an open source 
PDF workflow for a Linux fair in Germany I have some trouble. Shurely the 
partipicants of this list have enough inside to cope with the issues.

The PDF side seems ok with Ghostscript/CUPS for rendering and CinePaint 
and lcms for displaying. The test runs with the Altona Testsuite, a 
PDF/X-3 collection from ECI/UGRA/FOGRA.

The dithering of the propriarity driver is much smoother than 
Gutenprint's. The inkjet used is a Epson 3000. The device does 720 
dpi at a fixed drop size.
Now comparing the propriarity driver output with Gutenprint's rendering 
shows much more noice peaks in the Gutenprint dithering. It seems that
Gutenprint puts drops not so very well wighted. This is the case for b/w 
and for colour printing. The dithering is clearly a minus in the side by 
side comparision.

One problem seems to be in not taking the other colour planes into 
account. So for instance a black drop is too often placed next to a cyan 
one. Instead, as seen in the propriarity dithering, yellow can be placed 
near to black and cyan. Black and cyan should have the most distances 
followed by magenta and yellow. There is no such hierarchy obvious in 
Gutenprint's dithering results.

How does other open source drivers perform regarding smooth dithering?

Kai-Uwe Behrmann
                                + development for color management 
                                + imaging / panoramas
                                + email: ku.b at gmx.de
                                + http://www.behrmann.name

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