(gimpprint.info.gz) Weaving algorithms

(gimpprint.info.gz) Weaving introduction
 
 Weaving algorithms
 ==================
 
    I considered a few algorithms to perform the weave.  The first one I
 devised let me use only (jets-distance_between_jets+1) nozzles, or 25.
 This is OK in principle, but it's slower than using all nozzles.  By
 playing around with it some more, I came up with an algorithm that lets
 me use all of the nozzles, except near the top and bottom of the page.
 
    This still produces some banding, though.  Even better quality can be
 achieved by using multiple nozzles on the same line.  How do we do
 this?  In 1440x720 mode, we're printing two output lines at the same
 vertical position.  However, if we want four passes, we have to
 effectively print each line twice.  Actually doing this would increase
 the density, so what we do is print half the dots on each pass.  This
 produces near-perfect output, and it's far faster than using (pseudo)
 "MicroWeave".
 
    Yet another complication is how to get near the top and bottom of the
 page.  This algorithm lets us print to within one head width of the top
 of the page, and a bit more than one head width from the bottom.  That
 leaves a lot of blank space.  Doing the weave properly outside of this
 region is increasingly difficult as we get closer to the edge of the
 paper; in the interior region, any nozzle can print any line, but near
 the top and bottom edges, only some nozzles can print.  We originally
 handled this by using the naive way mentioned above near the borders,
 and switching over to the high quality method in the interior.
 Unfortunately, this meant that the quality is quite visibly degraded
 near the top and bottom of the page.  We have since devised better
 algorithms that allow printing to the extreme top and bottom of the
 region that can physically be printed, with only minimal loss of
 quality.
 
    Epson does not advertise that the printers can print at the very top
 of the page, although in practice most of them can.  The quality is
 degraded to some degree, and we have observed that in some cases not
 all of the dots get printed.  Epson may have decided that the
 degradation in quality is sufficient that printing in that region
 should not be allowed.  That is a valid decision, although we have
 taken another approach.
(gimpprint.info.gz) Weaving algorithms

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