[sane-devel] [janitorial] New backend: escl
paddy-hack at member.fsf.org
Tue Dec 17 11:36:14 GMT 2019
# Rearranging top-posted content to the bottom so the conversation makes
# logical sense again :-/
Thierry Hucard writes:
> Le 15 déc. 2019 à 19:56, à 19:56, Ulf Zibis <ulf.zibis at gmx.de> a écrit:
>>Am 15.12.19 um 19:43 schrieb thierry at ordissimo.com:
>>> Le 2019-12-15 18:34, Ulf Zibis a écrit:
>>>> Hi List,
>>>> Am 15.12.19 um 09:10 schrieb Olaf Meeuwissen:
>>>>> The backend currently only supports image data transfer in JPEG format
>>>>> but Thierry indicated he wanted to add support for PNG and PDF as well.
>>>> Would it be possible to also support the TIFF format, as for
>>>> black&white it is the best compressing with Fax G4 compression?
>>> I didn't see any device managing Tiff, send me the capability file,
>>> I could add the support.
>> In my understanding, it's not the scanner, which supports the TIFF
>> format, but it has to send raw (or lossless compressed) format, so
>> sane or the sane frontend could compress to TIFF.
> No the backend receives the scanner data (the jpeg format always seems
> to be present), it can be jpeg, png, pdf or octet-stream. I didn't see
> any tiff. The data is compressed and sent back to the frontend.
As Thierry indicated, the JPEG support by the escl backend is a matter
of the communication between the device and the backend. For any SANE
frontend, that doesn't really matter as the SANE Standard only allows
for a "raw" image format. Any backend *has* to convert to SANE's raw
image format before handing image data to the frontend.
Doing device-backend image data transfer using JPEG is lossy in all but
the most uncommon scenarios. That is, image quality suffers. If the
device-backend image data transfer can use PNG, which is not lossy, that
would be a big improvement, image quality-wise.
BTW, I fear that any PDF device-backend image data transfer is just a
JPEG image wrapped in PDF but that remains to be seen.
Wishful thinking says PNG-in-PDF is out there somewhere, maybe.
Hope this helps,
Olaf Meeuwissen, LPIC-2 FSF Associate Member since 2004-01-27
GnuPG key: F84A2DD9/B3C0 2F47 EA19 64F4 9F13 F43E B8A4 A88A F84A 2DD9
Support Free Software https://my.fsf.org/donate
Join the Free Software Foundation https://my.fsf.org/join
More information about the sane-devel