[sane-devel] Fujitsu JPEG Duplex Scanning
m. allan noah
kitno455 at gmail.com
Sun Jul 6 02:07:27 UTC 2008
On 7/5/08, m. allan noah <kitno455 at gmail.com> wrote:
> On 7/5/08, Simon Glass <sglass at bluewatersys.com> wrote:
> > Hi,
> > On a Fujitsu FI-5750C I get JPEG working fine on the flatbed, or when
> > using ADF on the front / back size simplex.
> > But when I scan duplex JPEG, I get an image which is only half as wide
> > as it should be, and seems to have 8 lines of valid data, then 8 lines
> > from somewhere else, etc. Also the JPEG apparently has about half its
> > size in extraneous data (I get a warning when loaded into gimp).
> fujitsu duplex scanners buffer the backside in their internal ram, and
> you can request all of the frontside, then request all of the
> backside. but, if the machine does not have enough ram to hold the
> backside, it may error. so, i default to alternating front/back reads,
> and buffer the backside in the backend. most machines can handle
> either of those approaches.
> jpeg duplex seems to be a different story- the machines only alternate
> or serialize, but not both, you have a machine that serializes, so the
> attempt to descramble it does the opposite.
> there seems to be no way to detect the proper format by querying the
> scanner, but i might be able to inspect the image data. let me look.
i invented a mechanism to determine the interlacing format while
scanning, and switch modes on the fly. I have tested with a small,
alternating scanner (fi-4120c2) and a large serialized scanner
(fi-4990C). Simon has confirmed that this fixes the issue for his
machines (one alternating, one serial) without hardcoding anything.
i also fixed the sane_get_parameters bug Simon pointed out in another
email. all users of the fujitsu backend should really update to v70,
to get these (and quite a few other) fixes.
"The truth is an offense, but not a sin"
More information about the sane-devel