Hi Olaf, thank you for your answer.
> I guess what you as a user really want is a frontend giving you an > option to set a gamma correction some way. Single value for RGB, maybe > three values for R, G and B each or even hand-crafted profiles. What > you as a frontend implementer really want is > > - a way to tell the backend to not muck with gamma at all and do > everything in software yourself, or > - a way to pass those settings to the backend and let that figure out > the best way to achieve what it's been asked to do (maybe with a hint > as to what constitutes best, e.g. speed, memory, image quality, etc.) No, that is not what I want. As a user, I want an option in the frontend that results in a reasonable default gamma correction, so I don’t have to choose anything in order to get a reasonably looking scan. Especially, I don’t want to calibrate my individual scanner just to obtain information that is the same for all scanners of that kind. To put it differently, the information about a scanner’s native gamma value, given by its CCD properties, is a natural property of the backend. Any gamma correction applied by hardware and/or in the backend is also a natural property of the backend. There should be a way to communicate resulting gamma from the backend to a frontend, so it can choose an appropriate default gamma correction. > The SANE backends are very much like a filter between the device and > your frontend. There was also talk about "middleware" and if that > enters the picture you really need to make sure who's going to take > responsibility for what so that what arrives at the frontend is the way > it's supposed to be. I am aware that multiple gamma correction is detrimental for quality, this is why an option to choose the gamma of backend output would be preferable over a read-only option to obtain the actual gamma. Thanks, Jürgen > >>> Am 13.10.2020 um 10:45 schrieb Olaf Meeuwissen <[email protected]>: >>> >>> Hi Jürgen, >>> >>> Jürgen Mellinger writes: >>> >>>> Specifying a gamma value for acquired scan data would greatly add to >>>> usability as well. >>> >>> That's already in the version 2 draft. See >>> >>> https://sane-project.gitlab.io/standard/draft-2/api.html#gamma-table-options >>> https://sane-project.gitlab.io/standard/draft-2/api.html#analog-gamma >>> >>> Both are for device-side gamma support and the standard discourages >>> emulation in the backend of the former and forbids for the latter. > > 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
