[sane-devel] Image Compression doesn't support in SANE protocal
hennebry at web.cs.ndsu.nodak.edu
Wed Aug 23 19:20:50 UTC 2006
On Wed, 23 Aug 2006, m. allan noah wrote:
> On Wed, 23 Aug 2006, Michael Hennebry wrote:
> > On Tue, 22 Aug 2006, m. allan noah wrote:
> >> On Tue, 22 Aug 2006, René Rebe wrote:
> >>> Well that stinks as you lose a lot of detail with the lossy jpeg
> >>> decompression.
> >> even worse, if you are running the thing over the net backend, you convert
> >> to huge bitmap just before you transfer it over the network!
> >>> Maybe let's add the JPEG frame type rather soon (even in SANE 1) and let's
> >>> add an IR (infra red) frame specification on the way as good film scanner
> >>> deliver for dust and the-like removal.
> > Perhaps with carefully crafted code,
> > decompression compression could be made an identity operation.
> > If not, perhaps it could be made idempotent.
The idea is to put a useful bound on the amount of damage
done by repeated decompressions and compressions.
The jpeg compression algorithms are not invertable.
For every jpeg compression algorithm, there are distinct X and Y
such that compression(X)=compression(Y).
The same might be true for decompression, but I'm not sure.
> > If one is going to do compression, perhaps it would be good
> > to have a non-loosy method as one of the options.
> agreed. zlib ok?
Mike hennebry at web.cs.ndsu.NoDak.edu
"it stands to reason that they weren't always called the ancients."
-- Daniel Jackson
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