Re: HP PhotoSmart strip lengths

Peter Kirchgessner (peter@kirchgessner.net)
Mon, 17 May 1999 21:06:56 +0200

john allen pitney wrote:
>
> Hi all!
>
> I'm playing with writing a little SANE frontend for my HP PhotoSmart. It's
> not going to be as general as xscanimage or XSane; I only want to duplicate
> the HP frontend (with improvements possibly) using GTK and SANE.
>
> I wonder if anyone doing HP backend development has any leads on getting
> the actual length of a film strip scan from the scanner? The method I've
> found for acquiring a preview scan of a strip of unknown length, is to
> scan the whole thing using the maximum length, buffer everything including
> the spurious bytes at the end, then quit sane and do sane_init again. Now,
> the HP backend reports a maximum scan length which corresponds to the
> actual length of the film strip. Unfortunately, this method has a couple
> of problems: I have to buffer a lot of junk then throw it away later, and
> the sane quit/restart cycle is a little slow.
>
> Is there any way to get the "end of film strip" signal from the scanner
> during the sane_read() loop?
>

Hi John Allen,

there is no such signal. After the film strip has moved into the scanner
you can inquire the extent of the strip. Before the strip has moved into
the scanner it reports the maximum supported extent. You can proof this
by using xscanimage:

Start it and you will see the maximum extent.
Start a preview to move the strip into the scanner.
Then change the scanmode to lineart. On that change sane will re-read
the values from the scanner and display the extent of the film strip.

> Also, I'm noticing that the image gets stretched in the Y direction for
> any exposure setting which does not have a 100% Red exposure, that is,
> only "Off" and "Negative" seem to have the proper dimensions. I might
> be remembering the effect I saw incorrectly, but I noticed something
> along these lines.
>
> I'm using a Photosmart R032, by the way.
>

My Photosmart R029 does not show the stretching. It shows such
stretching when scanning slides at resolutions which are not multiple of
300 dpi.

-- Peter

> Thanks!
>
> John Pitney
>
> --
> Source code, list archive, and docs: http://www.mostang.com/sane/
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-- 
Peter Kirchgessner
WWW:    http://www.kirchgessner.net
e-mail: peter@kirchgessner.net





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