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Xerox scanners and photocopiers randomly alter numbers in scanned documents

dkriesel.com

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Re: Xerox scanners and photocopiers randomly alter numbers in scanned documents

#31

Post by jamespo »

Retric wrote: post #26
lostlogin wrote: post #20

Earlier quoted context omitted.

It is amazing the things people expect to be emailed. Can you email me the MRI scan? It's over 1500 images. Can you email it?

Emailing the file or emailing a link to the file is just as useful. As long as you have an encrypted document sharing capability you should be able to say sure to just about anything. PS: Granted that's assuming fast networks. For 80+ Gig VM's sending a removable drive is often faster.

For a lot of end users, if it's not a proper attachment no end of grief is caused.

And encryption and file hosting causes more hassle in enterprise environments with unforgiving compliance policies.

Re: Xerox scanners and photocopiers randomly alter numbers in scanned documents

#33

Post by lostlogin »

sneak wrote: post #23
lostlogin wrote: post #20

Earlier quoted context omitted.

It is amazing the things people expect to be emailed. Can you email me the MRI scan? It's over 1500 images. Can you email it?

It's amazing to me the engineers who refuse to update their worldviews about normal people's mental models for "sending data" that still get amazed by this. The size of the files or the number of them are totally irrelevant.

Just to make it clear, I'm not an engineer (I'd like to be good enough to be considered one, but that's a long way off). I'm more of an enthusiastic amateur who knows enough to badly break things. And the people who ask most frequently ask are ortho surgeons with a patient asleep on the table. Anyone who waits until that late in the piece then asked for a 1.5gig email becuase they weren't organised enough to sort out access to images in the 3 month lead up to an operation is not a normal person.

Re: Xerox scanners and photocopiers randomly alter numbers in scanned documents

#34

Post by hga »

micheljansen wrote: post #32

Ouch, imagine this happens in a hospital with a prescription or something. It could really have some serious implications.

Indeed, I keep a copy of my lab results for the last N years because they sometimes get lost, once through no real fault of the doctor (http://en.wikipedia.org/wiki/2011_Joplin_tornado).

Grrr, I'm now going to have to view every lab report that's not an original with suspicion, and make sure my doctors aren't making recommendations due to screwed up copies.

Lossy compression is not an acceptable default for a general purpose device.

Re: Xerox scanners and photocopiers randomly alter numbers in scanned documents

#35

Post by simonster »

rly_ItsMe wrote: post #12
ElliotH wrote: post #3

I can't quite see the reason why you would lossily compress something when your machine's purpose is to duplicate things. Anyone got a reasonable reason for doing this?

In the good old days of analog copiers this would be impossible - the scanner send the light through a system of mirrors to the drum, the drum gets static charged, the toner is pulled on the charged parts and gets transferred to the transfer belt, here the paper has the opposite charge and pulls the toner off of the transfer belt, goes through the fusing unit and here is the toner 'burned' to the paper. End of Story…

I might have missed something, but my reading is that the article doesn't state or imply this happens with regular photocopies, only with scans to PDF.

Re: Xerox scanners and photocopiers randomly alter numbers in scanned documents

#36

Post by Someone »

ElliotH wrote: post #3

I can't quite see the reason why you would lossily compress something when your machine's purpose is to duplicate things. Anyone got a reasonable reason for doing this?

Others have pointed out a credible explanation: to have the document take less space on their hard disk.

However, it does not have to be compression, per se. Modern copiers want to correct all kinds of errors such as creases and staples. They also want to optimize the colors. To do that, they have logic for detecting what areas of the page are full-color and which are black and white, which are half-tone printed, which are text, line art, photograph, whether the paper might have aged, etc.

I don't know what tricks they use, but I do not rule out that they will replace 'looks somewhat dirty' patches with an 'obviously higher quality version' of them, and use too aggressive parameters in some of those heuristics.

Re: Xerox scanners and photocopiers randomly alter numbers in scanned documents

#37

Post by boas »

lostlogin wrote: post #33
sneak wrote: post #23

Earlier quoted context omitted.

It's amazing to me the engineers who refuse to update their worldviews about normal people's mental models for "sending data" that still get amazed by this. The size of the files or the number of them are totally irrelevant.

Just to make it clear, I'm not an engineer (I'd like to be good enough to be considered one, but that's a long way off). I'm more of an enthusiastic amateur who knows enough to badly break things. And the people who ask most frequently ask are ortho surgeons with a patient asleep on the table. Anyone who waits until that late in the piece then asked for a 1.5gig email becuase they weren't organised enough to sort out…

We developed an easy way to email and collaboratively view CT or MRI studies. http://www.claripacs.com.

Re: Xerox scanners and photocopiers randomly alter numbers in scanned documents

#39

Post by linohh »

This was predictable. JBIG2 is in no way secure for document processing, archiving or whatsoever. The image is sliced into small areas and a probabilistic matcher finds other areas that are similar. This way similar areas only have to be stored once.

Yeah right, you get it, don't you? They are similar, not equal. Whenever there's a probability less than 1, there's a complementary event with a probability larger than 0.

I wonder which prize idiot had the idea of using this algorithm in a copier. JBIG2 can only be used where mistakes won't mean the world is going to end. A photocopier is expected to copy. If the machines were used for digital document archiving, some companies will face a lot of trouble when the next tax audit is due.

Digital archives using this kind of lossy compression are not only worthless, they are dangerous. As the paper trail is usually shredded after successful redundant storage of the images, there will be no way of determining correctness of archived data.

This will make lawsuits a lot of fun in the future.

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