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"
