Hi, I'm finishing png support. Thierry
Télécharger BlueMail pour Android Le 17 déc. 2019 à 13:32, à 13:32, Ulf Zibis <[email protected]> a écrit: >Hi Olaf, > >Am 17.12.19 um 12:36 schrieb Olaf Meeuwissen: >> Thierry Hucard writes: >> >>> Le 15 déc. 2019 à 19:56, à 19:56, Ulf Zibis <[email protected]> a >écrit: >>>> Am 15.12.19 um 19:43 schrieb [email protected]: >>>>> 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, > >Yes it helps to understand the issue, much thanks. > >If escl becomes common in future, I can imagine, sane additionally >could >provide a JPEG format interface to benefit from the faster transmission >between scanner and backend, especially if the transport is over >network >and image quality doesn't matter so much. > >-Ulf
