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🚗 openalpr - Automated license plate reader

This repository is a fork of the primary repository with minor modifications to run on Raspian Buster and Ubuntu 18+ with OpenCV. The Open Horizon service alpr utilizes this repository to build Docker containers. Please refer to the Dockerfile for details.

About

OpenALPR is an open source Automatic License Plate Recognition library written in C++ with bindings in C#, Java, Node.js, Go, and Python. The library analyzes images and video streams to identify license plates. The output is the text representation of any license plate characters.

Check out a live online demo here: http://www.openalpr.com/demo-image.html

Installation

Outside of use in building the alpr service, see The Easy Way for installation on Debian LINUX.

✋ Remember to specify http://github.com/dcmartin/openalpr.git as the repository.

Usage

OpenALPR includes a command line utility: alpr. Options may be specified for a variety of needs:

alpr options

  • -c --country country code - Either us for USA or eu for Europe; default: us
  • --config config file - Path to the openalpr.conf file
  • -n --topn integer - Maximum possible plates to return; default: 10
  • --seek milliseconds - Seek to the specified millisecond in a video file; default: 0
  • -p --pattern pattern code - Pattern to match (e.g. H7*) for plate; default: none
  • --clock on/off - Measure the total time to process image and all plates; default: off
  • -j --json - Output recognition results in JSON format; default: false

Example

After successfully building the alpr executable use the shell script alpranno.sh to annotate the original image with all detected license plates, for example:

% cd example
% ../src/build/alpr --json ea7the.jpg | tee ea7the.json | jq '.'
{
  "version":2,
  "data_type":"alpr_results",
  "epoch_time":1583029314644,
  "img_width":636,
  "img_height":358,
  "processing_time_ms":250.124680,
  "regions_of_interest":[{"x":0,"y":0,"width":636,"height":358}],
  "results":[
    {
      "plate":"EA7THE",
        "confidence":91.147400,
        "matches_template":0,
        "plate_index":0,
        "region":"",
        "region_confidence":0,
        "processing_time_ms":63.775341,
        "requested_topn":10,
        "coordinates":[{"x":206,"y":163},{"x":391,"y":161},{"x":394,"y":245},{"x":207,"y":248}],
        "candidates":[
          {"plate":"EA7THE","confidence":91.147400,"matches_template":0},
          {"plate":"EA7TBE","confidence":81.818542,"matches_template":0},
          {"plate":"EA7TRE","confidence":79.659111,"matches_template":0},        
          {"plate":"EA7TE","confidence":79.018761,"matches_template":0},
          {"plate":"EA7T8E","confidence":78.560219,"matches_template":0},
          {"plate":"EA7IHE","confidence":78.108887,"matches_template":0},
          {"plate":"EA7HE","confidence":78.106224,"matches_template":0},
          {"plate":"EA7TME","confidence":78.101746,"matches_template":0},
          {"plate":"EA7THB","confidence":77.812828,"matches_template":0},
          {"plate":"EA7TH6","confidence":76.512367,"matches_template":0}
      ]
    }
  ]
}

alpranno.sh script

The script requires ImageMagick and jq software; to install on Debian LINUX:

sudo apt update -qq -y && sudo apt install -qq -y imagemagick jq

Use the the shell script to annotate the image; for example:

% ./alpranno.sh ea7the
ea7the-alpr.jpg

Output

Changelog & Releases

Releases are based on Semantic Versioning, and use the format of MAJOR.MINOR.PATCH. In a nutshell, the version will be incremented based on the following:

  • MAJOR: Incompatible or major changes.
  • MINOR: Backwards-compatible new features and enhancements.
  • PATCH: Backwards-compatible bugfixes and package updates.

Authors & contributors

David C Martin (github@dcmartin.com)