[sane-devel] bug with Canon N1240U in Lineart mode at 75 dpi?

[Gerhard Jaeger]

Hi Eric,

On Monday 24 October 2005 18:25, Eric Ding wrote:
> Gerhard,
>
> This picks up from a conversation almost a year old (from Nov/Dec 2004),
> but I hope it's not completely inscrutable as a result.  The issue I was
> looking at involved a problem with scanning in Lineart mode at low
> resolutions (75dpi or less) on a Canon n1240u scanner on my Gentoo Linux
> box.
>
> When we corresponded back and forth (see below), you suggested some
> tweaking of some values in plustek-usbdevs.c, and I responded that
> certain values seemed to do the trick.  I thought that would be the end
> of the conversation.
>
> However, since then, I've had problems... I'm using sane-backends
> 1.0.16rc2 on Gentoo (seems to be the same in this area as the release
> version), and I am now having problems (again?) scanning in Lineart mode
> at 75dpi.  Here's the table:
>
>     /* Gray mode MCLK settings */
>     { 7.0, 7.0, 6.0, 6.0, 6.0, 6.0, 6.0,  6.0,  6.0,  6.0 },
>     { 6.5, 6.5, 6.0, 6.0, 6.0, 6.0, 8.0, 12.0, 12.0, 12.0 }
>
> If I change the first value to 7.5, i.e.,
>
>     /* Gray mode MCLK settings */
>     { 7.5, 7.0, 6.0, 6.0, 6.0, 6.0, 6.0,  6.0,  6.0,  6.0 },
>     { 6.5, 6.5, 6.0, 6.0, 6.0, 6.0, 8.0, 12.0, 12.0, 12.0 }
>
> then my scanner happily scans in a Lineart image at 75 dpi.  Can/should
> this be tweaked in the official source?

probably yes. I'm doing currently some tests with the 1200dpi CanoScans
(LiDE25, LiDE30/N1240 and N1220), so when checking in that stuff next time
I'll add this increased value.

Thanx for checking that.
Gerhard