Compiling QR reader for python / Ubuntu 11.10

Steps that apparently worked to get a QR code reader compiled for python (2.7) un Ubuntu 11.10 64 bit as of 2011-11-30.

(an alternative to the steps here might be this: http://pyqrcode.sourceforge.net/ but that didn't work easily for me in recent Ubuntus)

These instructions:
http://hi.baidu.com/paulau/blog/item/915e860ffbf7032c6059f34c.html

cover most of the steps, but lots of details need changing now vs. 2008.

The PyQrcodec_Linux.tar.gz mentioned in various places on the web has disappeared from www.pedemonte.eu - in fact that whole domain is gone. You can get it from http://gentoo.mirrors.pair.com/distfiles/PyQrcodec_Linux.tar.gz

The instructions above say:

sudo apt-get install g++
sudo apt-get install python-dev
sudo apt-get install libcv-dev libcvaux-dev

in addition you now need

sudo apt-get install libhighgui-dev

Untar and cd into the PyQrCodec folder.

then edit setup.py and add

extra_compile_args = ['-fpermissive'],

before each of the "sources = ..." lines.

then in the shell run (once and once only)

for file in $(grep -lre BEGIN ./*|grep -v svn); do sed -e "s/_BEGIN_/_CV_BEGIN_/;s/_END_/_CV_END_/" $file -i; done

now python setup.py build and sudo python setup.py install
should work (with all kinds of warnings).

The how to use example should be:

import PyQrcodec
size, image = PyQrcodec.encode('www.example.com')
image.save('example.png')
status, text = PyQrcodec.decode('example.png')
print(text)

.encode() params are:

Definition:     PyQrcodec.encode(string, image_width=400,
  case_sensitive=True, version=5,
  error_correction_level='QR_ECLEVEL_L',
  encoding_hint='QR_MODE_AN')
Docstring:
  Returns a PIL image of the QR code generated
  from the given string

Note: for http://upload.wikimedia.org/wikipedia/commons/thumb/9/9b/Wikipedia_mobile_en.svg/220px-Wikipedia_mobile_en.svg.png I had to flatten the image (replace the transparent background) for decode() to work.