[sane-devel] grey 4bit/pixel

[Michael Hennebry]

On Sat, 19 Aug 2006, abel deuring wrote:

> Shashi Kumar M.S. wrote:
> > iam searching a scanner that supports at about 300 dpi and 4 bit /pixel grey
> > scanner. i found from the scanner that most of the scanner support 8/16 bit
> > depth in grey mode.
> >
> > is there any way to modify this code to support 4 bit grey scale depth per pixel.

Why?  What constitutes a good answer might depend on it.

> - look for a (documented) file format that supports 4 bit images (or
>   define your own format ;)
> - patch scanimage or another frontend so that it can write the scan
>   data in the format you selected. Alternatively, you can convert
>   existing 8 bit images, as produced by a Sane frontend, with a
>   converter program. I am not aware of any 4 bit image formats, but
>   if they exist, you might already find such a converter in the
>   usual Linux distributions. Otherwise, write one. The PPM, PGM, PBM
>   formats (default for scanimage output) are very simple, and it is

None of those formats support 4-bit data.
They do support maxlevel=15 data, but the data are represented with 8-bits.
PBM (P4) is one bit per pixel.  If you want you could stack 4 pbm images.

>   quite straightforward to read them with C, Python, Perl, Java or
>   whichever other programming language.

-- 
Mike   hennebry at web.cs.ndsu.NoDak.edu
"it stands to reason that they weren't always called the ancients."
                                                      --  Daniel Jackson