5 ms·

> This is not an OCR problem (as we switched off OCR on purpose), it is a lot worse – patches of the pixel data are randomly replaced in a very subtle and dange

> This is not an OCR problem (as we switched off OCR on purpose), it is a lot worse – patches of the pixel data are randomly replaced in a very subtle and dangerous way: The scanned images look correct at first glance, even though numbers may actually be incorrect. I have a habit of scanning invoices/statements/manuals etc to pdf and found the above quite alarming. Though I don't use Xerox (my scanner is Epson Perfection V39), I never considered the possibility that a scan of a document can result in altered numbers. How do I know if my scanner could also be affected in case it uses similar underlying software/setup?

abrichr 5y ago
From the article: > In the next section, there is a a short manual for you to reproduce the error and see of you are affected.
superjan 5y ago
If you scan in color/grayscale, it can’t use JBIG2 compression. The machine will likely use JPEG for lossy compression, could result in less crisp scans, but it eliminates this risk.
- askl 5y ago
  Or you could use JBIG2 with reasonable settings.
  - colinfinck 5y ago
    From the original post: "numbers seem to be mangled independently from the compression mode, which makes the issue hard to avoid"
    - ace2358 5y ago
      Reasonable settings meaning no compression setting which was mentioned to not have the issue
      - texasbigdata 5y ago
        Thanks would love a 45mb one page PDF
        bryanrasmussen 5y ago
        I would love not to send a scanned document with different numbers to my accountant, or to the IRS for that matter.
    - dinkelberg 5y ago
      What the author refers to are the three available compression modes on Xerox scanners, which are "normal", "higher", and "highest". It is not clear what that means exactly, but it is possible that all three of those are lossy compression modes. In my opinion, the only reasonable mode for JBIG2 is lossless, as the lossy mode of JBIG2 is, in general, prone to these character mangling issues. File sizes for lossless JBIG2 compression are already very low, so I would claim that using lossless is almost always worth it, unless character mangling is explicitly not a problem.
  - m3at 5y ago
    The author was using default settings, I think it's fair to call the defaults reasonable
dinkelberg 5y ago
You should be safe if your scanner uses either JPEG, lossless JBIG2 or other lossless compression. If however it uses lossy JBIG2 compression, it is quite possible that it suffers from the same problem, due to how lossy JBIG2 compression works.
- dreamcompiler 5y ago
  TFA suggests that Xerox was offering the option of lossless JBIG2 compression but they implemented it incorrectly -- they didn't include the delta blocks that described how individual image blocks differed from canonical patterns. Which brings up another point: How did Xerox's SW development process take place? Was it done in-house with frequent code reviews or was it outsourced to a low bidder and then thrown back over the wall with no real quality assurance process?
  - kevinpet 5y ago
    This isn't the kind of issue a code review would catch. Code review will find when the code isn't written to standards or doesn't look maintainable. It isn't going to catch a subtle misuse of a technique that should be valid.
    - flatiron 5y ago
      the review should also be reviewing the tests, and you should really have a test if you have a standard.
      - tablespoon 5y ago
        > the review should also be reviewing the tests, and you should really have a test if you have a standard. Codes reviews and unit tests aren't a substitute for QA or acceptance testing. It's great when code reviews do catch stuff like this, but that's not going to catch everything. To me this bug points to deficiencies in another part of the process.
      - mypalmike 5y ago
andi999 5y ago
Keep the originals.
zoomablemind 5y ago
I wonder if this may be also a problem with Samsung MFPs, as some Xerox consumer models were apparently OEM'd by Samsung (e.g. Samsung SCX-4200 vs. Xerox 3119, or was it the other way around?). Not sure if there's a list which links the Xerox-Samsung similar models. I guess, if the scanner offers JBIG2 format option, it may need a test at least.
- TomMasz 5y ago
  Xerox purchased a number of small desktop and larger machines from Samsung, including the one you mention.

abrichr 5y ago

From the article: > In the next section, there is a a short manual for you to reproduce the error and see of you are affected.

superjan 5y ago

If you scan in color/grayscale, it can’t use JBIG2 compression. The machine will likely use JPEG for lossy compression, could result in less crisp scans, but it eliminates this risk.

askl 5y ago
Or you could use JBIG2 with reasonable settings.
- colinfinck 5y ago
  From the original post: "numbers seem to be mangled independently from the compression mode, which makes the issue hard to avoid"
  - ace2358 5y ago
    Reasonable settings meaning no compression setting which was mentioned to not have the issue
    - texasbigdata 5y ago
      Thanks would love a 45mb one page PDF
      - bryanrasmussen 5y ago
        I would love not to send a scanned document with different numbers to my accountant, or to the IRS for that matter.
  - dinkelberg 5y ago
    What the author refers to are the three available compression modes on Xerox scanners, which are "normal", "higher", and "highest". It is not clear what that means exactly, but it is possible that all three of those are lossy compression modes. In my opinion, the only reasonable mode for JBIG2 is lossless, as the lossy mode of JBIG2 is, in general, prone to these character mangling issues. File sizes for lossless JBIG2 compression are already very low, so I would claim that using lossless is almost always worth it, unless character mangling is explicitly not a problem.
- m3at 5y ago
  The author was using default settings, I think it's fair to call the defaults reasonable

dinkelberg 5y ago

You should be safe if your scanner uses either JPEG, lossless JBIG2 or other lossless compression. If however it uses lossy JBIG2 compression, it is quite possible that it suffers from the same problem, due to how lossy JBIG2 compression works.

dreamcompiler 5y ago
TFA suggests that Xerox was offering the option of lossless JBIG2 compression but they implemented it incorrectly -- they didn't include the delta blocks that described how individual image blocks differed from canonical patterns. Which brings up another point: How did Xerox's SW development process take place? Was it done in-house with frequent code reviews or was it outsourced to a low bidder and then thrown back over the wall with no real quality assurance process?
- kevinpet 5y ago
  This isn't the kind of issue a code review would catch. Code review will find when the code isn't written to standards or doesn't look maintainable. It isn't going to catch a subtle misuse of a technique that should be valid.
  - flatiron 5y ago
    the review should also be reviewing the tests, and you should really have a test if you have a standard.
    - tablespoon 5y ago
      > the review should also be reviewing the tests, and you should really have a test if you have a standard. Codes reviews and unit tests aren't a substitute for QA or acceptance testing. It's great when code reviews do catch stuff like this, but that's not going to catch everything. To me this bug points to deficiencies in another part of the process.
    - mypalmike 5y ago

andi999 5y ago

Keep the originals.

zoomablemind 5y ago

I wonder if this may be also a problem with Samsung MFPs, as some Xerox consumer models were apparently OEM'd by Samsung (e.g. Samsung SCX-4200 vs. Xerox 3119, or was it the other way around?). Not sure if there's a list which links the Xerox-Samsung similar models. I guess, if the scanner offers JBIG2 format option, it may need a test at least.

TomMasz 5y ago
Xerox purchased a number of small desktop and larger machines from Samsung, including the one you mention.