OpenALPR is an open source Automated License Plate Recognition library written in C++. The library analyzes images and identifies license plates. The output is the text representation of any license plate characters found in the image.
Check out a live online demo here: http://www.openalpr.com/demo.html
OpenALPR includes a command line utility. Simply typing "alpr [image file path]" is enough to get started recognizing license plate images.
For example, the following output is created by analyzing this image:
The library is told that this is a Missouri (MO) license plate which validates the plate letters against a regional template.
user@linux:~/openalpr$ alpr ./samplecar.png -t mo -r ~/openalpr/runtime_dir/
plate0: top 10 results -- Processing Time = 58.1879ms.
- PE3R2X confidence: 88.9371 template_match: 1
- PE32X confidence: 78.1385 template_match: 0
- PE3R2 confidence: 77.5444 template_match: 0
- PE3R2Y confidence: 76.1448 template_match: 1
- P63R2X confidence: 72.9016 template_match: 0
- FE3R2X confidence: 72.1147 template_match: 1
- PE32 confidence: 66.7458 template_match: 0
- PE32Y confidence: 65.3462 template_match: 0
- P632X confidence: 62.1031 template_match: 0
- P63R2 confidence: 61.5089 template_match: 0
Detailed command line usage:
user@linux:~/openalpr$ alpr --help
USAGE:
alpr [-t <region code>] [-r <runtime_dir>] [-n <topN>]
[--seek <integer_ms>] [-c <country_code>]
[--clock] [-d] [-j] [--] [--version] [-h]
<image_file_path>
Where:
-t <region code>, --template_region <region code>
Attempt to match the plate number against a region template (e.g., md
for Maryland, ca for California)
-r <runtime_dir>, --runtime_dir <runtime_dir>
Path to the OpenAlpr runtime data directory
-n <topN>, --topn <topN>
Max number of possible plate numbers to return. Default=10
--seek <integer_ms>
Seek to the specied millisecond in a video file. Default=0
-c <country_code>, --country <country_code>
Country code to identify (either us for USA or eu for Europe).
Default=us
--clock
Measure/print the total time to process image and all plates.
Default=off
-d, --detect_region
Attempt to detect the region of the plate image. Default=off
-j, --json
Output recognition results in JSON format. Default=off
--, --ignore_rest
Ignores the rest of the labeled arguments following this flag.
--version
Displays version information and exits.
-h, --help
Displays usage information and exits.
<image_file_path>
(required) Image containing license plates
OpenAlpr Command Line Utility
OpenALPR compiles and runs on Linux, Mac OSX and Windows.
OpenALPR requires the following additional libraries:
- Tesseract OCR v3.x (https://code.google.com/p/tesseract-ocr/)
- OpenCV v2.4.x (http://opencv.org/)
After cloning this GitHub repository, you should download and extract Tesseract and OpenCV source code into their own directories. Compile both libraries.
Update the src/CMakeLists.txt file in the OpenALPR project. Update the following lines to match the directories of your libraries on your system:
- SET(OpenCV_DIR "../libraries/opencv/")
- SET(Tesseract_DIR "/home/mhill/projects/alpr/libraries/tesseract-ocr")
Finally, in the src directory, execute the following commands:
- cmake ./
- make
If all went well, there should be an executable named alpr along with libopenalpr.a that can be linked into your project.
Please post questions or comments to the Google group list: https://groups.google.com/forum/#!forum/openalpr
Affero GPLv3 http://www.gnu.org/licenses/agpl-3.0.html