[sane-devel] Additional frame types in Sane 1

[Oliver Rauch]

Am Sonntag, den 27.05.2007, 14:08 -0400 schrieb m. allan noah:

> > > >
> > > Well extending SANE1 will certainly start the new discussion
> > > about finishing SANE2 standard before starting - ACK ;)
> > > But as we did not move forward and scanner support for Linux
> > > is more or less stopped in its development, I vote for
> > > extending SANE1.
> > >
> > > As long as it won't hurt the API and the flow-control, introducing
> > > more frametypes should be no problem...
> >
> > Nice to see no big flamewar about the simple frametype addition :-)!

It really is nice that no flamewar starts here but I do not support to
extend SANE1 this way.

(see my following comment)

> > > >      SANE_FRAME_RGB,            /* pixel-interleaved red/green/blue bands */
> > > >      SANE_FRAME_RED,            /* red band only */
> > > >      SANE_FRAME_GREEN,          /* green band only */
> > > > -    SANE_FRAME_BLUE            /* blue band only */
> > > > +    SANE_FRAME_BLUE,           /* blue band only */
> > > > +    SANE_FRAME_INFRARED,       /* infra-red band */
> > > > +    SANE_FRAME_RGBI,           /* pixel-interleaved red/green/blue/infra-red */
> > > > +    SANE_FRAME_JPEG            /* Joint Photographic Experts Group's JPEG */
> > > >    }
> > > >  SANE_Frame;
> >
> > In the meantime I noticed the device can send Gray+IR as well which
> > would mean SANE_FRAME_GRAYI, as well.
> 
> i know you probably get RGBIRGBI... from the scanner, but for
> backwards compatability and to avoid the proliferation of frametypes-
> i propose to ONLY add SANE_FRAME_IR. Then an existing backend can add
> IR support to any other frametype by sending an extra frame, and
> existing frontends can be told to ignore the IR frame, and keep using
> the gray/rgb frames.

Although you do not change the function calls 
at the end you change the SANE API, a frontend that shall handle this
needs a lot of changes, also a backend needs a lot of changes.

A new backend will not work properly with an old frontend.


I suggest to do all this in SANE2 because it is incompatible to SANE1.
In the moment a frontend has to handle 3 modes:
GRAY
RGB
RGB 3-pass

With the new suggestions it would have to handle
GRAY
RGB
RGB 3pass
GRAY + INFRARED
RGB + INFRARED
RGB 3pass + INFRARED
RGBI
JPEG + INFRARED?
RED + INFRARED?
etc.

The change of the transmission format hast been put into SANE2
because it changes a lot in the comunication for frontends and backends.

Where is the advantage to put it into SANE1?
You will get incompatibilities between frontends and backends and you
slow down (if this is possible at all) the development of SANE2.

Finish the SANE2 standard. That solves all problems.

Oliver