OpenALPR Python binding failing when trying to load dll

Question

After downloading the precompiled binaries for Windows of the openALPR library, running the setup.py included in the source code to install it, and running the python_test.bat included in the precompiled binaries directory I get the following error:

File "C:\Users\rhenriquez\AppData\Local\Programs\Python\Python37-32\lib\site-packages\openalpr\openalpr.py", line 51, in __init__
    self._openalprpy_lib = ctypes.cdll.LoadLibrary("libopenalprpy.dll")
  File "C:\Users\rhenriquez\AppData\Local\Programs\Python\Python37-32\lib\ctypes\__init__.py", line 434, in LoadLibrary
    return self._dlltype(name)
  File "C:\Users\rhenriquez\AppData\Local\Programs\Python\Python37-32\lib\ctypes\__init__.py", line 356, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: OSError: [WinError 193] %1 is not a valid Win32 application

When I started to run the script at first the error was WinError 126 and then I noticed that the dll that the script was trying to call (openalprpy.dll) didn't had "lib" at the beginning of its name, so I added it to the dll's name. Then it started to send me WinError 193, and I've been clueless on what else to do or what am I doing wrong from then on.

Any help would be appreciated.

tgikal · Accepted Answer · 2019-01-23T19:27:36.440

EDIT: So I tried this with the 32-bit version and it gives the same error you are encountering. This appears to be an issue with trying to import a 32-bit .dll while using 64-bit python, or vice-versa, as seen in Python Ctypes Load Library

/EDIT

I did get it to work on my system... with a few modifications, this package is not as "plug and play" as it should be.

I don't know where I went right, so I'll just list what I did:

Download the pre-compiled biniaries from releases (I used openalpr-2.3.0-win-64bit.zip) https://github.com/openalpr/openalpr/releases

Download the project itself, https://github.com/openalpr/openalpr

Unzip both.

Goto the bindings folder in openalpr-master cd C:\openalpr-master\openalpr-master\src\bindings\python and run python setup.py install to make the bindings.

Then navigate to the project folder in site-packages, most likely C:\Users\rhenriquez\AppData\Local\Programs\Python\Python37-32\lib\site-packages\openalpr\ and open openalpr.py in IDLE,

here you can change line 51 from self._openalprpy_lib = ctypes.cdll.LoadLibrary("libopenalprpy.dll") to self._openalprpy_lib = ctypes.cdll.LoadLibrary("openalprpy.dll") since it appears other links are broken if you change the file name.

I also found it beneficial to change line 90 to except Exception: since it did not want to import correctly and was not raising an ImportError.

After that the python_test.bat worked correctly.

Namespace(config='openalpr.conf', country='us', plate_image='samples/us-1.jpg', runtime_data='runtime_data')
Using OpenALPR 2.3.0
Image size: 497x372
Processing Time: 561.825989
Plate #1
          Plate   Confidence
  -       THECAR   92.207481
  -       THEGAR   81.348961
  -        HECAR   80.229317
  -       TMECAR   78.159492
  -       THE0AR   77.702461
  -       THECAB   77.389000
  -        THEAR   76.510017
Press any key to continue . . .

Thank you so much!! Your edit was the one that did it for me. For some reason, I didn't pay attention and installed 32-bit Python instead of the 64-bit. Now it's working! Thank you! — Roy Henriquez, Jan 24 '19 at 13:45

OpenALPR Python binding failing when trying to load dll

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