[sane-devel] Canon-SCSI backend
I just made a few minor changes (fixed an uninitialized variable, inserted checks for return status of some subroutines). Sincerely yours, Ulrich Deiters
[sane-devel] Canon-SCSI backend
Hi, On Fri, Jan 10, 2003 at 08:16:35AM +0100, Ulrich Deiters wrote: I just made a few minor changes (fixed an uninitialized variable, inserted checks for return status of some subroutines). Ok. ChangeLog entry is missing :-) Bye, Henning
[sane-devel] Canon-SCSI backend
I remember very well the troubles I had with my FS2710S when I tried to upload gamma tables! The effects on the scans were very interesting from the artist's point of view - a *very* modern artist, in fact. :-) Now that I know the gamma table format the scanner recognizes I will try to play again with this feature, but I have some doubts about the success: Canon apparently does not use the gamma tables; furthermore, the standard controls of SCSI scanners like contrast or brightness are not responding at all. I agree that it would be better to handle such things within the scanner. But, according to Canon, we are not supposed to run the scanner without their software, and for them it may make sense to keep the scanner as simple as possible, while handling all the finer details of scanning by the computer. Best regards, Ulrich Deiters
[sane-devel] Canon-SCSI backend
Then, if gamma tables aren't supported (or at least aren't supported well), they shouldn't be offered to the frontend, right ? Not necessarily: The backend emulates the contrast, brightness, ... gamma options. This is even necessary for the FS2710, because it requires a huge gamma correction of about 2.5 to begin with, and the automatic optimization of xsane does not work well if it has to go to such extremes. Best regards, Ulrich Deiters
[sane-devel] Canon-SCSI backend
Dear Diego, thank you for the tip about the array length; I will check this. The FS2710 does not seem to be influenced by downloaded gamma tables. The original Canon (Windows) software feeds it 4 tables of 8192 byte length (2^12 entries of 2 byte length), but does not change them when you manually select another brightness, contrast, etc. . My guess is that Canon runs the scanner in 12-bit mode all the time, does the gamma correction in the computer, and then rounds the result to 8 bits. Our Canon backend does just that, and the results look the same as those obtained with their software. Incidentally, the Canon backend contains subroutines for the adjustment of contrast, brightness, shadow point, etc., that others might find useful. Best regards, Ulrich Deiters
[sane-devel] Canon-SCSI backend
Deiters wrote: thank you for the tip about the array length; I will check this. I hit the bug some time ago (around 25/10), and Henning Meier-Geinitz found it. The FS2710 does not seem to be influenced by downloaded gamma tables. Yep! It is. Or at least I've had MAJOR troubles when trying to adjust gamma by HW (about one year ago, IIRC). Then xsane started using SW gamma and the problem was gone. The original Canon (Windows) software feeds it 4 tables of 8192 byte length (2^12 entries of 2 byte length), but does not change them when you manually select another brightness, contrast, etc. . It should change them when you alter gamma table. Brightness and contrast are a different matter and never gave me troubles. My guess is that Canon runs the scanner in 12-bit mode all the time, does the gamma correction in the computer, and then rounds the result to 8 bits. Maybe. I really don't know enough details to tell what happens - and haven't windoze to test. Our Canon backend does just that, and the results look the same as those obtained with their software. That's good. IIRC, the problem was present when acquiring in 8-bit mode. Incidentally, the Canon backend contains subroutines for the adjustment of contrast, brightness, shadow point, etc., that others might find useful. Shouldn't those be done by the scanner itself, so to use the full range? Is multi-pass scanning supported? (well, not just sending more times the scan command, but acquiring a line multiple times before moving head to the next). BYtE, Diego.
[sane-devel] Canon-SCSI backend
I just re-compiled the Canon-SCSI backend on HP-UX 10.20. It seems to work. My congratulations to Mitsuru Okaniwa for a successful bug hunt! While playing with it I upgraded the support for Canon film scanners: The focus controls (manual and autofocus) for the FS2710S model are working now. The revised Canon backend (with Mitsurus's bug fix and the improved FS2710 support) can be downloaded from my FTP server (stthd0.pc.uni-koeln.de) by anonymous FTP: pub/canon-1.10.tar.gz Note: Use a ftp program to download it; http-browsers pointed at ftp://stthd0... will not get past our firewall. If I find out how to deal with CVS I might even upload the programs there. Best regards, Ulrich Deiters
