On Tue, 18 Aug 2009 09:40:05 -0400
"m. allan noah" <kitno455 at gmail.com> wrote:
> > In libksane I try to figure out a suitable scanning resolution by starting
> > with
> > 100 DPI, increasing the DPI with 100 until I reach 300 pixels height or
> > width.
> > The problem with epson2 is that the "pixels_per_line" parameter returned by
> > sane_get_parameters() is always 0. This means that the hard-coded limit of
> > 900
> > DPI is always reached (or the closest one).
> >
> > From the standard I understood that the value would be "best-effort
> > estimates"
> > before scan_start().
>
> Yes- the backend should make an attempt to at least guess the width of
> the scan prior to sane_start(). Does the original epson backend do
> this?
Hi,
this is code from epson.c
s->params.pixels_per_line =
SANE_UNFIX (s->val[OPT_BR_X].w - s->val[OPT_TL_X].w) / 25.4 * ndpi + 0.5;
and this is from epson2.c
s->params.pixels_per_line =
(SANE_UNFIX(s->val[OPT_BR_X].w - s->val[OPT_TL_X].w) / (MM_PER_INCH * dpi) )
+ 0.5;
^ ^
they're almost the same except for a parenthesis that changes the
order in which the operators are applied.
can you check if changing to
s->params.pixels_per_line =
((SANE_UNFIX(s->val[OPT_BR_X].w - s->val[OPT_TL_X].w) / MM_PER_INCH) * dpi )
+ 0.5;
resolves your issue?
--
Best regards,
Alessandro Zummo,
Tower Technologies - Torino, Italy
http://www.towertech.it
