# Re: SnapScan

From: Oliver Schwartz (Oliver.Schwartz@gmx.de)
Date: Fri May 05 2000 - 07:26:25 PDT

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  Hi,

  > > However, the RGB offsets as I understand them are not an offset in value but a
  > > spatial offset. E. g. if you scan a black square on white background in
  > > color mode it doesn't have sharp edges but maybe a blue edge on one side and an
  > > orange edge on the other. Just try it.
  >
  > This is interesting. Is there a solution/fix for this? I'm asking because I'm
  > in the process of implementing a correction for the same "feature" in the
  > EPSON Perfection 610 scanner.

  Obviously some effort has been made in the current snapscan backend, but for
  some reason the code is now marked as obsolete and #ifdef'ed. Most of it can
  be found in snapscan-310.c. If I understand the solution correctly it works as
  follows:

  The offset values are retrieved from the scanner using the inquiry command.
  Then every scanned line is stored in a ring buffer (with r, g and b value).
  Once there are enough lines in the ring buffer to synchronize r, g and b the
  lines can be read out again.

  There are some comments in the code that suggest that there is a RGBRouter
  somewhere that should replace the old sync routines but I haven't found any
  implementation for it.

  Another problem is that the inquiry command says that all offsets are 0 for my
  scanner...

  Oliver

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