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From: Paul 
Newsgroups: microsoft.public.windowsxp.general
Subject: Re: General question about QR code scanning
Date: Sat, 18 Nov 2017 21:03:51 -0500
Organization: A noiseless patient Spider
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J. P. Gilliver (John) wrote:
> In message , Paul  
> writes:
>> james@nospam.com wrote:
>>> I got a thing in the mail about using USPS (post office) to ship holiday
>>> gifts. It says to scan your QR code at home to speed up shipping. I know
>>> that a smartphone with an app can do this, using the phone's camera, but
>>> how can someone using a computer do this? (Or maybe it's not
>>> possible)....
>>>  I just take my stuff to the post office, but I always like to learn how
>>> this technology stuff all works....
> 
> Me too. I'm puzzled: how are you supposed to get the QR code to scan 
> before you've handed the parcel over the counter?
>>
>> Well, without knowing the answer, I'd say your machine
>> needs "vision". Your desktop would at least need a webcam.
>> Or alternately, if you have a point&shoot digital camera,
>> you could take a picture of the offensive QR code, and
>> load that into your computer.
> 
> Or a scanner of course.
>>
>> Then the next job, is getting a program to orient the
>> picture so it can be decoded, then convert it into
>> a URL for you.
>>
>> https://www.nextofwindows.com/how-to-scan-qr-code-on-your-pc
>>
>> So for fun, I took the picture of a QR code from that sample
>> article (cropped it in GIMP so just the QR squares were
>> in the picture), and uploaded it here.
>>
>> https://webqr.com/
> 
> Thanks for that - looks like a useful site. (Asked if I wanted to 
> "share" my webcam! I closed the asking box this time, but presumably if 
> I'd said yes, I could have held something with a QR in front of it!)
>>
>> And that site gave back a URL of "http://en.m.wikipedia.org".
>>
>> That means you don't even need a resident Win32 program
>> on your PC. You can also upload the image of the QR to
>> a web site and the web site can decode it for you. And
>> out comes a URL. Or other textual info.
>>
>>   Paul
>>
> In practice, are QR codes - at least on products, in magazine articles, 
> and the like - used for anything _other_ than URLs? I ask because I'm 
> off and on looking for something that will interpret them for my blind 
> friends (might well be an iPhone app.), but if all they normally contain 
> are URLs, I doubt they'd be that useful. (In that most things that have 
> them also have the URL printed nearby anyway, and OCR can do that for my 
> friends anyway - and URLs probably aren't much use to them anyway, given 
> the poor design [for VH/VI folk] of most web pages.)

The above is the first QR I've ever processed.
I couldn't tell you from first hand experience,
how many non-URL applications there are.

The article here shows a few uses for it, and it
can pass binary data. The interesting part
for me, is a claim it uses Reed Solomon code
(that's the same kind of error correcting code
used on CDs, to acquire data even when the disc
is scratched).

https://en.wikipedia.org/wiki/QR_code

    "The processor locates the three distinctive squares
     at the corners of the QR code image, using a smaller
     square (or multiple squares) near the fourth corner
     to normalize the image for size, orientation, and
     angle of viewing. The small dots throughout the QR
     code are then converted to binary numbers and
     validated with an error-correcting algorithm."

The RS interleave layout is presumably an attempt
to guess how the label will be damaged or defaced.
For example, there's one QR sample they show, which
still works, and a corner is missing. I think the
RS was interleaved the way it was, to handle cases
like this on purpose.

So we should be testing this one on that web site :-)

https://en.wikipedia.org/wiki/QR_code#/media/File:QR_Code_Damaged.jpg

    Paul
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