[sane-devel] Image Compression doesn't support in SANE protocal

m. allan noah anoah at pfeiffer.edu
Tue Aug 22 17:35:54 UTC 2006

On Tue, 22 Aug 2006, René Rebe wrote:

> On Aug 22, 2006, at 2:51 PM, m. allan noah wrote:
>> now that many low-end scanners support jpeg natively (some ONLY do jpeg!) i 
>> expect we will see more need for this.
> Oh!
>> as a short term fix, rather than adding a new sane_frame type, the backend 
>> can extract the compressed data, convert to raw bitmap. then frontend can 
>> convert to any compressed format it wants. this is not as efficient as 
>> keeping the compressed version the entire way through, but it works now.
>> dell networked scanner backend works this way.
> 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.

agreed. though i would think we would need to make a well-known option 
like 'compression' or 'format' that such backends would have to implement, 
with the default being 'bitmap'. these backends would then 'unjpeg' the 
files before passing to frontend, and existing frontends will continue to 
work. then the user must manually set the option to something other than 
'bitmap', if he knows his frontend supports this.

SANE2 could require that the frontend support jpeg, and that could become 
the default for the 'format' option.


> Yours,

"so don't tell us it can't be done, putting down what you don't know.
money isn't our god, integrity will free our souls" - Max Cavalera

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