On Sun, Jul 9, 2017 at 2:54 PM, Matt Garman <[email protected]> wrote: > Hi Allan, > > Thank you for taking the time to provide some feedback and look into this! > > More commentary inline below: > > On Fri, Jul 7, 2017 at 12:06 PM, m. allan noah <[email protected]> wrote: >> In general, if you are using swdeskew, it is probably better to scan >> at full width, and use the swcrop option too. Also, some fujitsu >> machines support the overscan option, which will cause the scanner to >> output some extra background rows before the paper is ingested. This >> can significantly improve the swdeskew performance. The S1500 does not >> have a black background option, but the larger scanners do, and this >> will also help. >> >> If you have a document that consistently reproduces poor deskewing, >> even with those additional options, I'd like to see a .pnm file of the >> scan with and without swdeskew enabled. > > Most of my documents have far too much personal info on them to > publish publicly... but we'll try to make due with some generic > documents. > > Here's a link to the output of "scanimage -h", just for reference for > what default settings are. I included the PDF as scanned under > Windows, and the PNM files from a Linux scan, both with and without > the --swdeskew option enabled. (There are two files for each of the > Linux/PNM, because it was a duplex scan, i.e. front and back. Windows > scan was also duplex, but the software concatenates all scans into one > file.) > > http://raw-sewage.net/images/linux_scansnap_s1500/ > > At any rate - this one doesn't demonstrate skew very well. But it > does sort of answer my previous question: you can see that when I used > the swdeskew option, it actually cut off part of the document. I > previously assumed the scanner was mis-judging the actual scan > area/document size, but from this simple experiment, it appears the > swdeskew can get confused and cutoff parts of the document.
Well, I got over my fear of clicking on 'raw sewage' and looked at a couple of your images. I agree that this is a bug, the swdeskew should not crop the top of the image in this case. I wonder- is that purple stripe near the left margin actually on the page, or does your scanner have a problem? > Under Linux, you can see I scanned at 300dpi. I have it set to "auto" > under Windows, but I'm quite sure it scanned at 300dpi or less. If I > specify anything over 300dpi (under either platform) the scanning is > noticeably slower. Not a precision measurement I know, but it's > something. I expect the sane driver to be equal or slightly faster than the windows driver. If you find otherwise, let me know. > >> All the options you list here are values which we send to the >> hardware. Frankly, I have little documentation about what they do, but >> it is certainly possible that some of these only have effect in binary >> mode, and they may not even work on the S1500. I'll see if I can track >> that down, and disable them in cases where they cannot be used. >> ( ... ) >> I'm willing to guess that much of what you are seeing is the windows >> software making a larger, potentially higher resolution or color mode >> scan, and then cleaning it up in software. > > I'm assuming similar open source tools exist for Linux; i.e. > scanimage/sane doesn't have to do all the work... I just want to get a > good, comprehensive scan out of sane. Then I can script a pipeline of > post-processing tools. There are some tools like unpaper and leptonica which can do some of these things. Perhaps they will be useful to you. Even still, I would like to fix bugs in sane if I can. I'll take a crack at it using your image. > I'll continue to look for non-personal documents to present more > examples. I created a Windows virtual machine so now I can quickly > test the two without having to turn on my old PC and switch the > keyboard/video/mouse cables over! > > Thanks again, let me know if I can provide any more info. > > -Matt allan -- "well, I stand up next to a mountain- and I chop it down with the edge of my hand" -- sane-devel mailing list: [email protected] http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/sane-devel Unsubscribe: Send mail with subject "unsubscribe your_password" to [email protected]
