As yet another side project I wanted to make use of my RPi camera + ANPR software to try and track down whoever is fly-tipping in my local estate. Since they dump their rubbish basically in full view of my living room, I’m looking to catch them in the act.
Attempt 1 – using the Raspbian packages (spoiler alert, it didn’t work)
Boring package install
sudo apt install openalpr openalpr-daemon openalpr-utils libopenalpr-dev
pip3 install openalpr picamera numpy
sudo apt-get install libatlas-base-dev
Get a test image wget http://plates.openalpr.com/ea7the.jpg
alpr -c us ea7the.jpg
Error opening data file /usr/share/openalpr/runtime_data/ocr/lus.traineddata
Please make sure the TESSDATA_PREFIX environment variable is set to your "tessdata" directory.
Failed loading language 'lus'
Tesseract couldn't load any languages!
Segmentation fault
Not good – so this is based on tesseract in the background. Looking around I see that the training data lives in tessdata, which is a subdirectory of ocr
/usr/share/openalpr/runtime_data/ocr/tessdata $ ls
lau.traineddata leu.traineddata lgb.traineddata lkr2.traineddata lkr.traineddata lsg.traineddata lus.traineddata
pi@raspberrypi:/usr/share/openalpr/runtime_data/ocr/tessdata $ mv ./* ../
pi@raspberrypi:/usr/share/openalpr/runtime_data $ tesseract --tessdata-dir /usr/share/openalpr/runtime_data/ocr/ --list-langs
Please make sure the TESSDATA_PREFIX environment variable is set to your "tessdata" directory.
List of available languages (7):
lau
leu
lgb
lkr
lkr2
lsg
lus
Ok, still not really making sense. Lets assume that OpenALPR is putting wrappers around the language so “us” becomes “lus” when fed to tesseract
pi@raspberrypi:/usr/share/openalpr/runtime_data/ocr $ tesseract -l lus ~/ea7the.jpg ./openalpr/runtime_data/config/us.conf
Error, could not create TXT output file: No such file or directory
Now that is more promising
alpr -c us ea7the.jpg
plate0: 10 results
- EA7THE confidence: 91.0578
- EA7TBE confidence: 84.133
- EA7T8E confidence: 83.0083
- EA7TRE confidence: 82.7869
- EA7TE confidence: 82.5961
- EA7TME confidence: 80.2908
- EA7TH6 confidence: 77.0045
- EA7THB confidence: 75.5779
- EA7TH confidence: 74.6576
- EA7TB6 confidence: 70.0797
Now lets take our python bindings for a spin
Python 3.7.3 (default, Dec 20 2019, 18:57:59)
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
import json
from openalpr import Alpr
alpr = Alpr("us", "/etc/openalpr/openalpr.conf", "/usr/share/openalpr/runtimedata")
Traceback (most recent call last):
File "", line 1, in
File "/home/pi/.local/lib/python3.7/site-packages/openalpr/openalpr.py", line 91, in init
self._initialize_func = self._openalprpy_lib.openalpr_init
File "/usr/lib/python3.7/ctypes/init.py", line 369, in getattr
func = self.getitem(name)
File "/usr/lib/python3.7/ctypes/init.py", line 374, in getitem
func = self._FuncPtr((name_or_ordinal, self))
AttributeError: /usr/lib/libopenalpr.so.2: undefined symbol: openalpr_init
Much Google time later and it seems that this is down to the pre-build python bindings not matching the version of the package that I’ve installed. Fsck it anyway
pi@raspberrypi:~/.local/lib/python3.7/site-packages $ pip3 show openalpr
Name: openalpr
Version: 1.1.0
Summary: OpenALPR Python Bindings
Home-page: http://www.openalpr.com/
Author: Matt Hill
Author-email: [email protected]
License: UNKNOWN
Location: /home/pi/.local/lib/python3.7/site-packages
Requires:
Required-by:
Attempt 2 – Build from master
Use git to clone from the master
Install the required packages
sudo apt-get install build-essential
sudo apt-get install cmake git libgtk2.0-dev pkg-config libavcodec-dev libavformat-dev libswscale-dev
sudo apt-get install libopencv-dev libtesseract-dev git cmake build-essential libleptonica-dev
sudo apt-get install libcurl4-openssl-dev
sudo apt-get install liblog4cplus-dev
Build and install OpenAPNR and the python bindings
cd openalpr/src
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr -DCMAKE_INSTALL_SYSCONFDIR:PATH=/etc ..
make
sudo make install
cd ../bindings/python
sudo python3 setup.py install
Now we can make progress
pi@raspberrypi:~ $ python3
Python 3.7.3 (default, Dec 20 2019, 18:57:59)
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import locale
>>> locale.setlocale(locale.LC_ALL, 'C')
'C'
>>> from openalpr import Alpr
>>> alpr = Alpr("us", "/etc/openalpr/openalpr.conf", "/usr/share/openalpr/runtime_data")
>>> import json
>>>
>>> results = alpr.recognize_file("/home/pi/ea7the.jpg")
>>>
>>> print(json.dumps(results, indent=4))
{
"version": 2,
"data_type": "alpr_results",
"epoch_time": 1589218326623,
"img_width": 636,
"img_height": 358,
"processing_time_ms": 234.429916,
"regions_of_interest": [
{
"x": 0,
"y": 0,
"width": 636,
"height": 358
}
],
"results": [
{
"plate": "EA7THE",
"confidence": 91.05777,
"matches_template": 0,
"plate_index": 0,
"region": "",
"region_confidence": 0,
"processing_time_ms": 59.747936,
"requested_topn": 25,
"coordinates": [
{
"x": 208,
"y": 157
},
{
"x": 393,
"y": 157
},
{
"x": 393,
"y": 245
},
{
"x": 208,
"y": 245
}
],
"candidates": [
{
"plate": "EA7THE",
"confidence": 91.05777,
"matches_template": 0
},
{
"plate": "EA7TBE",
"confidence": 84.132973,
"matches_template": 0
},
Where is the “openalpr/src” directory located?
Missed the git clone. I ran this, but still it’s broken.
Traceback (most recent call last):
File “”, line 1, in
File “/usr/local/lib/python3.7/dist-packages/openalpr/openalpr.py”, line 85, in __init__
self._recognize_raw_image_func = self._openalprpy_lib.recognizeRawImage
File “/usr/lib/python3.7/ctypes/__init__.py”, line 369, in __getattr__
func = self.__getitem__(name)
File “/usr/lib/python3.7/ctypes/__init__.py”, line 374, in __getitem__
func = self._FuncPtr((name_or_ordinal, self))
AttributeError: /lib/libopenalprpy.so: undefined symbol: recognizeRawImage