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<TITLE>sane-devel: Duplex (was: Fujitsu M3091 backend)</TITLE>
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<META NAME="Author" CONTENT="Frederik Ramm (frederik@remote.org)">
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<META NAME="Subject" CONTENT="Duplex (was: Fujitsu M3091 backend)">
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<H1>Duplex (was: Fujitsu M3091 backend)</H1>
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<!-- received="Tue Feb 27 11:53:41 2001" -->
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<!-- sent="Tue, 27 Feb 2001 20:06:20 +0000" -->
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<!-- name="Frederik Ramm" -->
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<!-- subject="Duplex (was: Fujitsu M3091 backend)" -->
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<!-- id="20010227200620.A11963@aruba.remote.org" -->
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<!-- inreplyto="01022720404600.00591@slowcrap" -->
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<STRONG>From:</STRONG> Frederik Ramm (<A HREF="mailto:frederik@remote.org?Subject=Re:%20Duplex%20(was:%20Fujitsu%20M3091%20backend)&In-Reply-To=<20010227200620.A11963@aruba.remote.org>"><EM>frederik@remote.org</EM></A>)<BR>
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<STRONG>Date:</STRONG> Tue Feb 27 2001 - 12:06:20 PST
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<P>
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<LI><STRONG>Next message:</STRONG> <A HREF="0240.html">Davis, Tom: "RE: Fujitsu fi-4750C Backend Project"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0238.html">mh: "Re: Writing Fujitsu M3091 backend"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0238.html">mh: "Re: Writing Fujitsu M3091 backend"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0237.html">Oliver Rauch: "Re: Writing Fujitsu M3091 backend"</A>
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<HR NOSHADE><P>
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<P>
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Hi,
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<BR>
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<P><EM>> > > When scanning the first page, half the data goes in this large buffer,
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</EM><BR>
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<EM>> > > then when the frontend asks for another page it comes out of the
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</EM><BR>
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<EM>> > > buffer very quickly.
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</EM><BR>
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[...]
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<BR>
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<P><EM>> > That sounds reasonable. But can I be sure that front-ends will support
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</EM><BR>
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<EM>> > reading multiple pages one after the other with no call to ..._close()
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</EM><BR>
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[...]
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<BR>
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<P><EM>> You can't be sure, but you can be quite sure that at least the graphical
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</EM><BR>
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<EM>> frontends won't call sane_close() between scans.
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</EM><BR>
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<EM>> On the whole, it's just an insufficiency in the current SANE Standard.
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</EM><BR>
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<P><P>Let's do it as suggested then. I'll introduce a switch that's called
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<BR>
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"duplex" and can be set to on or off; when "on", it will allocate a
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<BR>
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chunk of memory upon starting the scan and deliver that at the next
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<BR>
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request for image acquisition. - Would it make sense store the current
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<BR>
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settings along with that buffer, and only deliver the second page if a
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<BR>
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subsequent request is made *without changing* the settings (dpi,
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<BR>
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window size etc.)?
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<BR>
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<P>I was thinking of maybe adding a third setting, "duplex=hack" or some
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<BR>
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such, where the resulting image would be exactly twice as high (or
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<BR>
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twice as wide) as requested, and it would contain the front and back
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<BR>
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pages above each other (or next to each other).
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<BR>
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<P>That would not make a lot of sense with the graphical front-ends, but
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<BR>
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somebody using "scanimage" could then use that option and easily
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<BR>
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separate the images with pnmcut afterwards.
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<BR>
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<P>Would I run into trouble trying to return an image that is twice as
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<BR>
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big as originally requested by the front-end?
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<BR>
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<P>Bye
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<BR>
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Frederik
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<BR>
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<P><PRE>
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--
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Frederik Ramm ## eMail <A HREF="mailto:frederik@remote.org?Subject=Re:%20Duplex%20(was:%20Fujitsu%20M3091%20backend)&In-Reply-To=<20010227200620.A11963@aruba.remote.org>">frederik@remote.org</A> ## N57<35>48.10' W005<30>40.32'
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<P><P>--
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Source code, list archive, and docs: <A HREF="http://www.mostang.com/sane/">http://www.mostang.com/sane/</A>
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To unsubscribe: echo unsubscribe sane-devel | mail <A HREF="mailto:majordomo@mostang.com?Subject=Re:%20Duplex%20(was:%20Fujitsu%20M3091%20backend)&In-Reply-To=<20010227200620.A11963@aruba.remote.org>">majordomo@mostang.com</A>
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</PRE>
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<LI><STRONG>Next message:</STRONG> <A HREF="0240.html">Davis, Tom: "RE: Fujitsu fi-4750C Backend Project"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0238.html">mh: "Re: Writing Fujitsu M3091 backend"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0238.html">mh: "Re: Writing Fujitsu M3091 backend"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0237.html">Oliver Rauch: "Re: Writing Fujitsu M3091 backend"</A>
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<EM>
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This archive was generated by <A HREF="http://www.hypermail.org/">hypermail 2b29</A>
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: <EM>Tue Feb 27 2001 - 11:55:10 PST</EM>
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