[sane-devel] Scan quality enhancements/processing (vs Windows with Fujitsu ScanSnap S1500)

[Roger]

> On Mon, Jul 03, 2017 at 03:02:59PM -0500, Matt Garman wrote:
>TL;DR: for those of you who have migrated your document scanning
>workflow from Windows to a Sane platform (e.g. Linux), what
>settings/tools have you found to maintain or improve quality of
>scanned documents (relative to Windows)?
>
>Long version:
>
>I have a Fujitsu ScanScan s1500 document scanner, and sane-1.0.27
>running on Arch Linux.  So far it seems to just work.  I've had this
>scanner for nearly a decade, and used it exclusively under Windows
>until now (trying to move to a pure Linux desktop).
>
>So while I can scan documents just fine, the results to me aren't as
>good as what I get under Windows using the proprietary ScanSnap
>software.  Specifically, they are too light/too dark, text not crisp
>enough, straight lines not straight, colors a bit off, etc.

In my experience, the Windows or proprietary solutions usually utilize 
significant software processing after the original data is acquired from the 
scan.

Most experienced users (eg. photographers, ...) tend to desire vanilla scanned 
results or data, for either realistic/exact results or for legal reasons.  I 
personally just cannot stand to see a scan of negative media being processed 
with overly satured colors, rather than seeing the original colors of a 
negative!  I personally prefer an original vanilla scanned image for archiving 
purposes.  I then, if needed, augment the image later.

Most people in Linux/Unix world, desire one tool for one specific task.  
Sane/XSane gets the data in the computer.  Other separate tools are utilized 
later for improving an image.

>One example: de-skewing.  All the years I've had this scanner, I
>didn't even realize this was a thing until now.  I can use scanimage's
>software de-skewing (--swdeskew=yes), and it seems to *mostly* work,
>but pages are often still somewhat skewed.  Excepting for
>wacky/unusual documents, I don't recall ever seeing any skew under
>Windows.
>
>Despeckling (--swdespeck=n) does seem to be a major step in the right direction.
>
>I'm also playing with all the enhancement options.  E.g.,
>--brightness, --contrast, --emphasis, etc.  Brightness and contrast
>are fairly intuitive, but I don't really understand what the other
>options actually mean, or what I should expect from them.  I've been
>taking the trial-and-error approach, but e.g. --variance doesn't seem
>to do anything.  And I'm not sure how the options interact with each
>other, so trial-and-error could take forever.
>
>Having said all that, my one test document is maybe 90% as "good" as
>the same scanned on Windows.  Probably good enough to live with, but:

The command line sane tool is pretty basic in my brief experience.  The XSane 
interface seems to perform a better job than some of those command line 
switches, unless somebody else wants to pipe-in here.  It maybe, XSane uses the 
sane program libraries (eg. routines/functions) a little bit better to get 
better results than the sane command line tool.

>(1) This seems to be a very popular scanner - has anyone been able to
>back out the settings the proprietary ScanSnap software uses?
>- and -
>(2) I wonder if the Windows ScanSnap software settings are static or
>dynamic?  E.g., is there some kind of pre-processing algorithm applied
>to guess at the best enhancement settings?

My Canon 9000f Windows' proprietary software when scanning negative media, will 
apply post-processing to saturate the image with colors the Canon 9000f 
software thinks are good-looking versus VueScan's more realistic colors.  I 
believe the software also straightens the images as well.  Amazingly, all this 
proprietary post-processing is not able to be turned-off within the proprietary 
software!  Quite commonly, this post-processing or processes other than 
scanning the target, can usually all be performed better using other tools such 
as ImageMagick, Gimp, etc ...  because this post-processing is more well 
maintained elsewhere and those other tools' development is usually more well 
focused, as well as being updated more frequently.

>As for 3rd party tools, I've read about unpaper, and played a bit with
>scantailor, but (outside of OCR), they don't seem to offer more
>enhancement features than sane itself (or I'm overlooking something).

I just heard about unpaper too as well, likely something you'll be definitely 
desiring to use.

>Any other rules of thumb or general pointers for getting the best out
>of my scanner with Sane?

VueScan likely does all you're probably wanting as well, but think you're doing 
fine using open source.  The main reason I use VueScan, is for old 
ancestry/genealogy negatives and VueScan is well proven for photography uses.  
I don't get much time here, and the media is very time sensitive.

Personally, I prefer command line tools; as it's far easier to pipe tasks to 
other utilities.  For document processing, you'll probably have a far easier 
time creating a script.

-- 
Roger
http://rogerx.freeshell.org/
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