[sane-devel] pixma MP810 working with sane

[m. allan noah]

On Tue, Sep 2, 2008 at 4:59 PM, Nicolas <nicolas.martin at freesurf.fr> wrote:
> Hi,
>
> Concerning the vertical lines at 4800/2400 dpi for MP810, I'm wondering
> whether:
>
> - this is a normal behavior of the scanner (which would mean that it has
> to be compensated by the backend),
> - or if it's an alignment problem of the sensor, the lines corresponding
> each one to a particular sensor cell, but only at high dpi, the sensor
> uses all its cells to scan.
>
> I think it may be interesting that other MP810 users could give feedack
> on the current CVS backend, if possible, that's why I copy also the
> sane-devel list
>
> Do you know if there's an alignment procedure for MP810 ? This is
> usually the case when you get a new scanning device.
>
> Have you the possibility to test the Canon Windows driver, and see if it
> behaves the same ?
>
> FYI, the particular image encoding used by pixma devices at high dpi
> (giving a subset of images to be merged) is the same on newer generation
> devices (like MP610 with CIS sensor, or MP970 with CCD), but for those
> models, there's no effect of vertical lines, all cells are correctly
> aligned up to 4800 dpi.
>
> Also, I've not seen samples of scanned images for other older pixma
> devices (like MP600, MP960, ...), currently not supporting 2400 or 4800
> dpi mode, but I'would be interested to know if those devices produces
> also such image subsets (which means it could be very easy to have them
> fully supported also by the pixma backend).
>
> Last point concerning the white lines at the bottom: this is simply due
> to the color planes shifting, as the backend algorithm to shift the
> color planes uses only that portion of the image that will contain data
> for the 3 colors. The bottom of the scanned image contains 2 and 1 color
> zones only, due to the color shift.
> So this is a little limitation for pixma CCD sensors, you must select a
> scan zone a little bit bigger at the bottom, then remove the image
> bottom white zone, that is padded on purpose by the backend to keep the
> image size the frontend expects.
> Another solution would have been to send to the frontend a smaller
> image, but this may raise some errors then in the frontend ...
>

i handle this specific issue for the old fujitsu M3091/2 by requesting
a few more lines from the scanner than the user asked for, and throw
away the extra ones after i shift the color planes.

allan
-- 
"The truth is an offense, but not a sin"