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

[Gerard Klaver]

On Tue, 2006-08-22 at 13:35 -0400, m. allan noah wrote:
> 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.
> 
> allan
> 
> >
> > Yours,
> >
> 
Also for webcam devices the jpeg option is a welcome feature, devices
like pac207 and sq930c/b support jpeg (and many other webcam usb
bridges).
-- 
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m.vr.gr.
Gerard Klaver