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Xerox scanners and photocopiers randomly alter numbers in scanned documents

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

#81

Post by ams6110 »

lotharbot wrote: post #64
epistasis wrote: post #61

Earlier quoted context omitted.

But we're not dealing with barns or letters or any physical object, we're dealing with abstract systems where the physics are much more flexible and changeable. It's important to change our computer systems to work for us, rather than attempting to change people to adapt to the computer systems. We should discard those systems that can not adapt to humanity, as they are of little worth in the long run. When somebody…

There are some pieces of content for which it's entirely impractical to "grant access via e-mail". On occasion people ask to be e-mailed extremely large blocks of data, where it would literally be faster to burn it to a pile of DVDs and then FedEx them than to upload-and-then-download the data. Depending on the size of the medical images mentioned in a previous post, that might actually be the case in that circumstan…

Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway

Andrew Tanenbaum

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

#82

Post by ams6110 »

michaelt wrote: post #53
lotharbot wrote: post #42

Earlier quoted context omitted.

Normal people seem to get that it's considerably harder to ship a barn than a letter, and that if you want to move a barn you use a specialty service rather than the post office. The size and number of files are and should be totally relevant even to "normal" people. When someone asks for something in e-mail, it's perfectly reasonable to say "no, it's much too big" and expect them to understand.

I think we can all agree that e-mails should have finite size - it's not a very good protocol for transferring multi-gigabyte files, for sure! Where we would disagree is where that limit should be drawn. I've seen systems in this day and age that fail in the face of e-mails as small as 5 megabytes (e.g. Yahoo Popgate) which IMHO is far too low - but evidently some sysadmins disagree with me!

Opinions run the gamut. I'm firmly in the "email should be plain text" camp but realized that battle was lost long ago.

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

#83

Post by jws »

rdtsc wrote: post #74
scrumper wrote: post #70

I don't think it's necessarily an issue of inexcusable incompetence: it seems like one of those faults which is obvious in retrospect but very difficult to predict. Why shouldn't Xerox use a standard compression algorithm in their scanner/copiers? That would seem to be a safer choice than writing a lossy compression algorithm from scratch. QA testing probably was on the order of 'picture looks right'; after all, why…

> Why shouldn't Xerox use a standard compression algorithm in their scanner/copiers? I have never heard of JBIG2. I implemented JPEG2000 codecs from scratch, arithmetic coding compression and I have never heard of JBIG2. And here the are using and it others claiming it is just a standard run of the mill thing. > That would seem to be a safer choice than writing a lossy compression algorithm from scratch. Going out on…

JBIG2 is hardly obscure. It is billed just as prominently on the official JPEG site as JPEG and JPEG2000.

It is useless to someone that wants to compress arbitrary images, since it is bi-level only, I'd ignore it too if I wanted to compress a photograph. Not having an open specification hurts. The "last draft" is available, but the final was sacrificed to someone's business model.

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

#84

Post by linohh »

hga wrote: post #78
linohh wrote: post #73

Earlier quoted context omitted.

CCITT Group 4 also known as Modified Modified Read is in no way something you'd be wanting to use now ever . I'm telling you why MMR sucks hard: 1. It's monochrome. No greyscale, no color. This works for text and lines, but nothing else. No big surprise, it was designed for Fax. But this makes CCITT G3 and G4 lossy. 2. It has no defined endianess. This adds another fault risk which you won't see coming as long as you…

Errr, I didn't communicate clearly. What I meant to say was that CCITT Group IV gave acceptable sizes for early-'90s computing power, CPU and disk, and something at or better than its level of lossless compression today should be even more acceptable. And in light of this screwup, I suspect we'd agree that Xerox would have been better off to use lossless (well, after the scanning, as you point out, but then again no…

Of course they would have been better off with T.6, as Group 4 at least did not modify the image content. However especially with TIFF there are/were countless implementations of viewers, components, libraries and every single one of them had their own habits. Some would not regard endianess, some would assume payload endianess is the same as the TIFF, some did respect the Tag for byte order specific to the image. When I coded my first TIFF Library, I was around 14 and the most troublesome part of doing it was keeping myself from bashing my head against the next available wall due to stupidity of other people who thought interpreting a standard according to their wishes was ok, because there'd never be someone trying to display the images with a viewer different from theirs.

I don't know how deep you have dived into TIFF, but maybe you remember the TIFF6 Standard way of embedding JPEG. It was the biggest pain in the ass imaginable, having to parse JPEG files, splitting them and packaging it into different TIFF Tags. Before TTN2 and easy embedding of JPEG Images, everyone invented their own way of avoiding the standard. Some defined their own compression type, some used the standard compression type, but used it in a nonstandard way, ah, I'm starting to lose my hair again ;-)

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

#85

Post by epistasis »

lotharbot wrote: post #64
epistasis wrote: post #61

Earlier quoted context omitted.

But we're not dealing with barns or letters or any physical object, we're dealing with abstract systems where the physics are much more flexible and changeable. It's important to change our computer systems to work for us, rather than attempting to change people to adapt to the computer systems. We should discard those systems that can not adapt to humanity, as they are of little worth in the long run. When somebody…

There are some pieces of content for which it's entirely impractical to "grant access via e-mail". On occasion people ask to be e-mailed extremely large blocks of data, where it would literally be faster to burn it to a pile of DVDs and then FedEx them than to upload-and-then-download the data. Depending on the size of the medical images mentioned in a previous post, that might actually be the case in that circumstan…

> But it's a failure of people when they don't recognize the possibility that some types of data (video, large numbers of images, scientific research data, whole databases) simply can't be sent quickly, yet they fail to plan ahead to gain access. (I've also entirely skirted the issue of "some data should have its access restricted physically"...)

I disagree vehemently with that attitude, and I have to deal with it everyday. In my field, >50% of the data we receive is transferred by overnight courier of hard drives due to quantity of data. It's a crappy attitude to blame people for having to learn that, and in an ideal world we'd share it via access granted by email. People should not be blamed for not understanding that, our infrastructure should be blamed for not supporting 10Gb everywhere, and cheap access to 40Gb+ on long-distance connections.

Nothing is helped by blaming people, and relationships can be harmed by doing that. But we can change the technology.

As a side note, DVDs? Really? They're incredibly slow at data transfer once you have them in hand, the tiny size of a DVD requires tricky archive spanning methods, and optical discs are flaky technology all around. Hard drives or LTO-5/6 all the way.

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

#86

Post by rdtsc »

jws wrote: post #83
rdtsc wrote: post #74

Earlier quoted context omitted.

> Why shouldn't Xerox use a standard compression algorithm in their scanner/copiers? I have never heard of JBIG2. I implemented JPEG2000 codecs from scratch, arithmetic coding compression and I have never heard of JBIG2. And here the are using and it others claiming it is just a standard run of the mill thing. > That would seem to be a safer choice than writing a lossy compression algorithm from scratch. Going out on…

JBIG2 is hardly obscure. It is billed just as prominently on the official JPEG site as JPEG and JPEG2000. It is useless to someone that wants to compress arbitrary images, since it is bi-level only, I'd ignore it too if I wanted to compress a photograph. Not having an open specification hurts. The "last draft" is available, but the final was sacrificed to someone's business model.

You are right, I was just saying I was playing with image compression and just hadn't found JBIG2. Also probably because it has a patent associated with it and it is mainly for bi-level images.

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

#87

Post by WalterBright »

mikeash wrote: post #51
Canada wrote: post #25

That's what you get when you use lossy compression, and it's hardly a problem unique to Xerox scanners. Maybe important documents should be scanned to a higher resolution so you don't have problems like this.

Could you share with us a list of other scanners that have this problem, so we can avoid them?

I tried various compression and density settings on my Fujitsu scanner, and didn't see any problems like those mentioned in the article.

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

#89

Post by ygra »

yew wrote: post #63

Minor correction: The article says that the JBIG2 patch size might be the size of the scanned text. JBIG2 actually has the capability to detect regions of text and compress them using a specialized technique that operates on individual symbols. I suspect Xerox is using this option and their implementation is getting confused (perhaps by the low resolution). Unless I'm greatly mistaken, the patch size for normal compr…

I was confused by that as well. From what I understood how JBIG2 worked, those symbols don't even have to have the same size everywhere (as would be quite common with proportional fonts anyway). So there is no "patch size" per se; just the low resolution confusing the classifier.

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

#90

Post by NamTaf »

Do we know the scope of likely affected printers? The company I work at runs a whole heap (~80) of WorkCentre 3220, 4150 and 4250s, as well as ApeosPorts, etc.

I shudder to think how much we've scanned that could be affected by this. Thankfully, I think all of our engineering drawings (which for a decade+ were printed, signed, then scanned when needed for digital issue) were done on a non-xerox device, but all of our standard A3/A4 business stuff is done on Xerox devices.

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