I believe that most backends are doing no transformation at all. Since most backends are reverse engineered, I think we consider ourselves lucky just to get image data out of the scanner. If the blacks look black, and the whites look white, we ship it :)
allan On Sun, Jul 5, 2020 at 10:38 AM Jürgen Mellinger <juergen.mellin...@t-online.de> wrote: > > Hi, > > many SANE backends provide gamma correction options, but I could not find any > information about the default color space in which scan data are being sent > to sane_read(). I mean, if there is no custom gamma table used, then a > backend should be able to use its knowledge about a scanner’s CCD’s gamma > value to transform it into a pre-defined color space, such as sRGB, or linear > gamma. If there is no such pre-defined color space, then each and every user > will have to determine the correct gamma for their each and every scanner, > and perform custom gamma correction just to obtain a reasonable image. > > From this I suspect that SANE backends indeed transform scanner data into a > standard color space. My experience with the genesys backend suggests that > it’s linear gamma. But I cannot find any documentation on this issue. > > Could someone point me to more information on this topic? > > Thank you, > Jürgen -- "well, I stand up next to a mountain- and I chop it down with the edge of my hand"
