The following examples show how to use OpenALPR's prewarp configuration generated by the camera calibration utility. In the latter example this is combined with the ability to crop multiple regions of the image.

The license plates recognized after each preprocess rule are combined into a single JSON response.

Poll URL for an image every 10 seconds

docker run flyingtophat/alpr http://example.com/traffic_cam \
  --interval 10 \
  --verbose

Pre-process each image retrieved from URL before recognition

docker run flyingtophat/alpr http://example.com/traffic_cam \
  --verbose \
  --preprocess planar,429.000000,300.000000,-0.000000,0.000000,0.670000,1.000000,1.000000,0.000000,0.000000

The rule passed in is the value generated by OpenALPR's camera calibration utility. Further information on the value can be found in OpenALPR's configuration file for the prewarp option

Pre-process cropped regions of the image retrieved from URL before recognition

docker run flyingtophat/alpr http://example.com/traffic_cam \
  --verbose \
  --preprocess 0,0,435,299=planar,429.000000,300.000000,-0.000000,0.000000,0.670000,1.000000,1.000000,0.000000,0.000000 \
  --preprocess 435,0,705,299=planar,272.000000,300.000000,-0.000000,0.000000,-0.650000,1.000000,1.000000,0.000000,0.000000

In this example the prewarp rules are applied to their respective cropped area (<x1,y1,x2,y2>=) and all license plates are combined into a single JSON response.