[sane-devel] New release of the alpha version of hp5400 SANE backend

[Martijn van Oosterhout]

On Thu, Mar 06, 2003 at 11:05:29AM +1100, Martijn van Oosterhout wrote:
> > From the code I see that command 0x1500 always writes 300,
> > perhaps this needs to be changed to the same DPI value written
> > with command 0x2505?
> 
> No! Don't do that. That value is (as far as we know) the units that the
> SCANREQUEST values (offx/y, lenx/y) are given in. If you fiddle with that it
> stasrt going off to scan the wrong area of the page.

Looks like I need to eat my words here :) I just did a dump of the windows
scanner at high res and yes, that is one of the things we need to change.
What we have now works good for resolutions <= 300dpi. But for higher res
stuff you need to do the following:

Set Base DPI to RES (command 0x1500)
Calibrate scan at RES x 300dpi with light on
Calibrate scan at RES x 300dpi with light off
Set calibration table with 12 * RES bytes + padding
Do actual scan at RES x RES dpi

Note, for all scans you must scale various values as appropriate, otherwise
you're not scanning the right area. Also, some of the fields overflow at
2400dpi, so we need to handle that.

Once we've done that we can go back to the question of how it's formatted.

-- 
Martijn van Oosterhout   <kleptog at svana.org>   http://svana.org/kleptog/
> Support bacteria! They're the only culture some people have.
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