Xerox scanners and photocopiers randomly alter numbers in scanned documents

#1

Post by sxp » Sun, Aug 04, 2013, 5:23 PM UTC

Xerox scanners and photocopiers randomly alter numbers in scanned documents
dkriesel.com

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

#2

Post by hga » Sun, Aug 04, 2013, 5:40 PM UTC

Ack! Looks like overclever compression in a domain where it's not always desired, let alone required.

I spent half a decade on document imaging in the early to mid '90s, a fair amount close to this level (had a coworker who loved bit level stuff for the truly evil problems like this), and I can see how it happened ... given sufficiently careless developers.

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

#3

Post by ElliotH » Sun, Aug 04, 2013, 5:44 PM UTC

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?

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

#4

Post by nsxwolf » Sun, Aug 04, 2013, 5:45 PM UTC

Truly surprising. I would never have imagined this to be in the domain of possible problems one would expect to encounter scanning or photocopying a document.

It is like taking a picture of my wife with a digital camera and her face being replaced with that of some other person.

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

#5

Post by gcr » Sun, Aug 04, 2013, 5:46 PM UTC

nsxwolf wrote: post #4

Truly surprising. I would never have imagined this to be in the domain of possible problems one would expect to encounter scanning or photocopying a document. It is like taking a picture of my wife with a digital camera and her face being replaced with that of some other person.

That's quite possible. http://www.cs.columbia.edu/CAVE/projects/face_replace/

I can imagine someone turning the technique into a novel form of image compression, maybe for surveillance databases or something.

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

#6

Post by dietrichepp » Sun, Aug 04, 2013, 5:47 PM UTC

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?

The article has been updated with the probable cause for this error.

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

#7

Post by wahnfrieden » Sun, Aug 04, 2013, 5:47 PM UTC

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?

Cheaper components, maybe? (If it lets them get by with less memory for example.)

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

#8

Post by wahnfrieden » Sun, Aug 04, 2013, 5:48 PM UTC

Cached copy, which is missing the updated content: http://webcache.googleusercontent.com/search?q=cache%3Awww.d...

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

#9

Post by Gravityloss » Sun, Aug 04, 2013, 5:53 PM UTC

gcr wrote: post #5

nsxwolf wrote: post #4

Truly surprising. I would never have imagined this to be in the domain of possible problems one would expect to encounter scanning or photocopying a document. It is like taking a picture of my wife with a digital camera and her face being replaced with that of some other person.

That's quite possible. http://www.cs.columbia.edu/CAVE/projects/face_replace/ I can imagine someone turning the technique into a novel form of image compression, maybe for surveillance databases or something.

Think how someone could falsify your entire life...

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

#10

Post by hga » Sun, Aug 04, 2013, 5:57 PM UTC

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?

Good point. Looking at a product page (http://www.office.xerox.com/multifunction-printer/color-mult...), I see that the first model mentioned is multifunction, it can "Copy, email, fax, print, [and] scan".

So it sounds like there's one code path and it's seriously broken. I looked at the first settings page, and while it's in German I can see it's 200 DPI. There's no excuse for default lossy compression when you're at 200 DPI and doing office sized paper. We didn't do that in 1991, we got CCITT Group 4 lossless compression of around 50KB per image plus or more generally minus for 8.5x11 inch paper, although we did do thinks like noise reduction and straightening documents (that makes them compress better, among other things).