[sane-devel] Progress on CanoScan D1250U2

[Henning Meier-Geinitz]

Hi,

On Tue, May 13, 2003 at 10:11:55AM +0200, Norbert LATAILLE wrote:
> I started to work on the D1250U2 scanner some time ago, and I now 
> starting to have a standalone program (using libusb) which is producing 
> scanned BMP files under linux (24-bit mode, 75 dpi for now).

Nice! Do you have a web page or ftp site where you can place your code
and the information you gathered? So we could link from the scanner
list to that page. Otherwise I'll just link to your mail in the
mailing list archive.

Is the information at
http://www.mostang.com/pipermail/sane-devel/2003-January/017146.html
correct?

> However, something still confuses me about the color managment of this 
> scanner. Except from extra lines produced by the scanner, I have got 6 
> times more bytes than the number of pixels in the image. At first I 
> said: "fine, this is a 48-bit scanner after all". In fact it is producing:

Depends on the mode you selected. Maybe it's easier to start with
gray/8bit (if you know how to select the mode).

> RGB RGB RGB RGB ... RGB [line0]
> RGB RGB RGB RGB ... RGB [line0-bis]
> RGB RGB RGB RGB ... RGB [line1]
> RGB RGB RGB RGB ... RGB [line1-bis]
> ...
> RGB RGB RGB RGB ... RGB [lastline]
> RGB RGB RGB RGB ... RGB [lastline-bis]
> 
> Where [line0-bis] is somewhat different from [line0], and also different 
>  from the TWAIN output. I really seems like the scanner is doing its 
> job in 75dpix150dpi leaving to me the job of merging lines (but this 
> would not be 48-bits scanning). I believe that we will get more clues 
> when moving to another resolution.

> Here is my question: what is the standard output of a 48-bit scanner in 
> other drivers ? LSB/MSB bytes ? 2 lines ?

There is no "standard output". E.g. the gt68xx scanners can do at
least the follwing:

RR RR RR RR RR...
GG GG GG GG GG...
BB BB BB BB BB...

That's 16 bit line mode (little endian, I think).

RR GG BB RR GG BB...

That's 16 bit pixel mode.

> Another question is: what minimal features are expected by sane ? at 
> least choosing scanning resolution ? choosing color mode ? setting 
> shading data ?

Basically you don't need to provide any options in a SANE backend (but
the "number of options" option :-). To make the backend useful, it
should have at least the geometry options I think. Mode selection
(gray/color/lineart/whatever), resolution and maybe bit depth are
useful, too.

Bye,
  Henning