General - Automatic License Plate Recognition
These docs are for iSpy - See Agent DVR Docs for our new platform

What is ANPR?

ANPR stands for Automatic Number Plate Recognition. Depending on where you are in the world this may also be called Automatic License Plate Recognition or Car Plate Recognition or just License Plate Recognition (LPR).

ANPR is the process by which computers can recognise license plates. This can be useful in many scenarios for example:

  • Automatically opening gates/ doors for authorised vehicles
  • Alerting on unrecognised vehicles parking in your car spot or driveway
  • Alerting on unrecognised vehicles parking in reserved spots
  • Traffic monitoring and recognition
  • Car Park usage monitoring

How does it work?

iSpy has a plugin for ANPR that extracts license plates with an 85-95% success rate.

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There is a 7 day trial available after which you will need to license it to continue using it.. The plugin can alert on recognised or not recognised plates. You can integrate the LPR plugin to your own software by setting up the plugin to HTTP POST the LPR results to a URL of your choice (including frame grab, plate text and plate location - multiple plates per frame are supported).

Install Instructions

  • Download the plugin and extract the zip file to the plugins directory, (c:\program files\ispy\ispy\plugins)
  • Restart iSpy
  • Edit your camera, choose the alerts tab, select LPR in the drop down and click the "..." button to configure it.
  • Drag out an area to monitor for number plates in the main window. Select your country and other options on the right
  • Tip: To cut down on CPU use you can tell ispy to only scan for plates when it detects movement - on the alerts tab check the box under the alert type dropdown marked "When Motion Detected". You can also set it up to scan on a trigger - select "On Trigger" and use the http or command line interface (look for "triggerplugin") to trigger the plugin
  • If you need help integrating it with your own software please contact us

Plugin Configuration





  • Drag out an area to monitor for plates in the main window.
  • Overlay Results: Draw rectangles and detected plates on the live video stream
  • Country: Select your country (iSpyLPR has been optimised for different countries). This plugin does not currently work on USA plates
  • Min Confidence: The minimum level of confidence required to trigger a successful plate notification
  • Display: Display the detected confidence level on screen
  • Min Samples: The minimum number of successful identical results to trigger a successful plate notification
  • Scan Interval: The time in ms between scans
  • Min Characters: The minimum number of characters on the plate
  • Max Char Height: The maximum height of characters (in px)
  • Normalise Plates: Replace commonly misidentified characters


This tab lets you integrate ispy/ LPR with your own code/ software. The detected plates are sent to your batch files or http end points. All detected plates are sent regardless of whether they are in your alert list or not.

  • Location Name: The name of the location, eg: Car Port 1
  • URL: The HTTP URL to POST results to. iSpyLPR will post a JPEG image (called grab.jpg) along with the "plate", "area" and "location" in the querystring. The area is a CSV of numbers corresponding to a rectangle (x,y,w,h). This makes it easy to integrate iSpyLPR with your own backend software.
  • Code example for retrieving results from the HTTP POST (c#):
         string plate = Request.QueryString["plate"];
        string[] xywh = Request.QueryString["area"].ToString().Split(',');
        string location = Request.QueryString["location"];
        Bitmap bmp = new Bitmap(Request.Files[0].InputStream);
        //integrate plate, area, location and plate image with your systems
  • Executable: Call an executable or batch file with the detected plate and a path to the saved image (useful for gate opening software/ scripts)
  • Folder: Choose a folder to save captured images of license plates
  • Filename: Enter a template for the generated filenames. For example {PLATE}.jpg. You can also use {DATE} or {TIME}
  • Create CSV File: Create a CSV file in the grabs folder called "plates.csv" with the following format:


The plugin will generate an alert on the camera when a plate is detected that is either in the list or not in the list.

  • In List: Trigger an alert if the detected plate is in this list. An example list is: ABC123,BCD234,CDE345. Do not use new line or quotes in the CSV string.
  • Not In List: Trigger an alert if the detected plate is not in this list (leave blank to disable)*
  • Continuous Alerts: Continuously alert whilst the plate is visible instead of raise one alert when a plate is first recognised.

*By default, iSpy will only generate an alert every 180 seconds. You can modify this from the alerts tab when editing the camera.


Plugin version information and license activation. To license the ALPR plugin you need to use this tab and generate a license key.

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