QRCodeEncoder fails

[karolyi]

Hey,

I'm trying to convert the string 'B-4-1-20170805-6' into a QR-Code, but pyStrich raises an error:

Python 3.6.1 (default, Mar 22 2017, 06:17:05)
[GCC 6.3.0 20170321] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from pystrich.qrcode import QRCodeEncoder
>>> encoder = QRCodeEncoder('B-4-1-20170805-6')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/project/venv/lib/python3.6/site-packages/pystrich/qrcode/__init__.py", line 30, in __init__
    self.matrix = enc.encode(text, ecl)
  File "/project/venv/lib/python3.6/site-packages/pystrich/qrcode/textencoder.py", line 78, in encode
    self.create_matrix()
  File "/project/venv/lib/python3.6/site-packages/pystrich/qrcode/textencoder.py", line 197, in create_matrix
    matrix_content = self.minfo.create_matrix(self.version, self.codewords)
  File "/project/venv/lib/python3.6/site-packages/pystrich/qrcode/isodata.py", line 100, in create_matrix
    codeword_i = codewords[i]
IndexError: list index out of range

please investigate.

cheers

[edkirin]

Another bug report for this issue:

`
In [13]: from pystrich.qrcode import QRCodeEncoder

In [14]: encoder = QRCodeEncoder('00231872347699829949')

IndexError Traceback (most recent call last)
in ()
----> 1 encoder = QRCodeEncoder('00231872347699829949')

/home/eden/env/pdfworker2/lib/python3.5/site-packages/pystrich/qrcode/init.py in init(self, text, ecl)
28
29 enc = TextEncoder()
---> 30 self.matrix = enc.encode(text, ecl)
31 self.height = 0
32 self.width = 0

/home/eden/env/pdfworker2/lib/python3.5/site-packages/pystrich/qrcode/textencoder.py in encode(self, text, ecl)
76 "Codewords: " + ' '.join([str(codeword) for codeword in self.codewords]))
77
---> 78 self.create_matrix()
79
80 return self.matrix

/home/eden/env/pdfworker2/lib/python3.5/site-packages/pystrich/qrcode/textencoder.py in create_matrix(self)
195 """Create QR Code matrix"""
196
--> 197 matrix_content = self.minfo.create_matrix(self.version, self.codewords)
198 self.mtx_size = len(matrix_content)
199

/home/eden/env/pdfworker2/lib/python3.5/site-packages/pystrich/qrcode/isodata.py in create_matrix(self, version, codewords)
95 i = 0
96 while i < max_codewords:
---> 97 codeword_i = codewords[i]
98 j = 7
99 while j >= 0:

IndexError: list index out of range

`

[MrSurly]

Also having this problem.

[karolyi]

@MrSurly @edkirin and anyone else who has this problem, consider changing to https://github.com/lincolnloop/python-qrcode

[edkirin]

@karolyi Thanks for info, I will check this lib.

[MrSurly]

@karolyi I was looking for a generic library that does DMTX and QR, since my present QR generator makes rather large codes that don't print very clearly on my tiny labels.

[karolyi]

@MrSurly I feel you. I also wanted to use a more generic purpose data code imager library like this, but since this doesn't work and seemingly has no support, I was forced to change to the other one.

[MrSurly]

@karolyi I'm probably also going to change over -- has more control over the final size of the QR code, which is what I'm looking for, though I would like an API for accessing the individual pixels.

[mmulqueen]

I've had a look at this today. Ultimately, the code of this project is a mess and the tests are too high level to really help narrow down what's going on. This library is a Python 3 port of huBarcode (itself seemingly abandoned), with various improvements, but certainly not a re-write. If you run git blame on the responsible lines of code, you'll see that most of them are over a decade old.

I regularly use the code39, code128 and datamatrix aspects of this library, so I know those are relatively battle tested. I don't use the ean or qrcode parts. I've got some knowledge about how code39, code128 and datamatrix work and I've read a good chunk of the standardisation documentation about them. I know almost nothing about qrcode.

It looks to me like this bug only affects certain strings. It disappears by changing the case of the letter B in B-4-1-20170805-6 or changing one of the digits in 00231872347699829948. Digging deeper, it appears that error originates from the error correction codewords being 1 word too short. Everything else like the padding looks fine to me (again, I'm no expert).

So you're more than welcome to find the root cause and submit a patch. My recommendation would be to use a library that's better maintained for QR. The linked python-qrcode looks a lot cleaner to me in terms of implementation (no reliance on mysterious .dat files) - I can actually understand what's going on. I'd ideally drop QR support from this library, but I know people are using it.

This project is unlikely to receive major updates. I'd favour a re-write over trying to improve most of the existing code - this is something else that I don't currently have time for.

EDIT: Forgot to add. This bug is also present in huBarcode, so is unrelated to the port to Python 3. I haven't found a bug report for it though.

[darkfader]

My workaround was just to iterate through the various levels of redundancy until it passes. I only used used it for small numbers though.