[Gimp-print-devel] Highest quality modes for some Epson printers

[Robert L K. <rl...@al...>]

All of the new Epson printers (except for the infamous 440) now
support the "720 dpi highest quality" and "1440x720 highest quality"
modes.  I fixed the weave code to support 8x weave.  It actually
turned out to be very straightforward.

This essentially eliminates all horizontal banding.  However, there's
still a problem that I haven't tracked down.  There's what appears to
be some kind of misregistration between the two subpasses, which
creates some weird stippling that's visible under a loupe.  Edges also
aren't sharp, and when I inspect vertical edges very closely (at
normal 1440), there appears to be a very slight diagonal bias, along
with very slight vertical banding.  I don't know if that means my
print head is slightly out of alignment or if there's some very subtle
bug still lurking.

The way that the highest quality modes work is by assigning each
printed dot in a row to one of two (or, in 720x720 highest quality,
four) sub-rows, each of which is printed in a separate pass.  This is
done by alternating which dot (not which position) gets assigned to
which sub-row.  If I change the assignment routine to assign all of
the dots to one of the sub-rows or the other, everything works well.

The output as parsed by parse-escp2 looks correct.  With all printing
diverted to one of the two sub-rows, all of the expected rows do get
printed.

I'm still looking at this, but I don't expect a quick resolution...

-- 
Robert Krawitz <rl...@al...>      http://www.tiac.net/users/rlk/

Tall Clubs International  --  http://www.tall.org/ or 1-888-IM-TALL-2
Member of the League for Programming Freedom -- mail lp...@uu...
Project lead for The Gimp Print --  http://gimp-print.sourceforge.net

"Linux doesn't dictate how I work, I dictate how Linux works."
--Eric Crampton