[sane-devel] test backend: 1 bit RGB data for grid pattern

Oliver Schwartz Oliver.Schwartz@gmx.de
Wed, 25 Sep 2002 21:32:04 +0200


On Wednesday 25 September 2002 21:05, Henning Meier-Geinitz wrote:
> Hi,
> On Wed, Sep 25, 2002 at 11:16:15AM -0700, David Mosberger-Tang wrote:
> >   Oliver> I think that makes sense.  When a backend really does
> >   Oliver> support this then it can send it as 8 bit rgb image.
> >
> > Do we know for a fact that there are no high-speed devices out there
> > that produce, say, dithered 1-bit data?  If not, inflating the storag=
> > and bandwidth requirements for such devices by a factor of 8 seems
> > like a non-trivial issue.
> The older Mustek SCSI scanners could send 1 bit per color RGB so there
> are devices that can.=20

The Snapscan scanners also support 1 bit per color. You can even send you=
r own=20
dither matrix to the scanner. (In theory, that is. I never quite got it t=
work.) However, the backend will expand the data to 8 bit/color, so origi=
problem does not appear in the snapscan backend.

> But I have never seen the benefit. I mean, 2
> "colors", black and white are ok. 256 (or more) also. But 8? Ok,
> that's like CGA (?).
> What to do with these images? I mean, it's RGB so it can't be "lineart
> + some IR stuff".

IMHO it only makes sense if the scanner does some sort of dithering. The=20
dithered image may be send to a raster printer directly. This will save y=
the conversion / dithering on the host PC. In such a case, 1 bit/colour m=
make sense.