SimpleLPR

SimpleLPR is a software component for vehicle license plate recognition. It has a very simple programming interface that allows applications to supply a path to an image or a buffer in memory and returns the detected license plate text and its location in the input image. It can be used from C++, .NET-enabled programming languages, or Python.

Typical detection rates range between 85% and 95%, provided the license plates are in good condition, free of obstructions, and the text height is at least 20 pixels.

For further information, please download the user's guide and the class reference for .NET.

You can submit your questions/issues/bug reports/feedback to [e-mail]

Integration is simple and straightforward, as demonstrated in the following example:

using System;
using System.Collections.Generic;
using SimpleLPR3;

namespace TestSimpleLPR
{
    class Program
    {
    static void Main(string[] args)
    {
            // Create an instance of the SimpleLPR engine.
            EngineSetupParms setupP;
            setupP.cudaDeviceId = -1; // Select CPU
            setupP.enableImageProcessingWithGPU = false;
            setupP.enableClassificationWithGPU = false;
            setupP.maxConcurrentImageProcessingOps = 0;  // Use the default value.  

            ISimpleLPR lpr = SimpleLPR.Setup(setupP);

            // Output the version number
            VersionNumber ver = lpr.versionNumber;
            Console.WriteLine("SimpleLPR version {0}.{1}.{2}.{3}", ver.A, ver.B, ver.C, ver.D);

            try
            {
                bool bOk = (args.Length == 2 || args.Length == 3);
                if (bOk)
                {
                    string sFilePath = args[1];

                    // Configure country weights based on the selected country
                    uint countryId = uint.Parse(args[0]);

                    if (countryId >= lpr.numSupportedCountries)
                        throw new Exception("Invalid country id");

                    for (uint ui = 0; ui < lpr.numSupportedCountries; ++ui)
                        lpr.set_countryWeight(ui, 0.0f);

                    lpr.set_countryWeight(countryId, 1.0f);

                    lpr.realizeCountryWeights();

                    // Set the product key (if supplied)
                    if (args.Length == 3)
                        lpr.set_productKey(args[2]);

                    // Create a processor object
                    IProcessor proc = lpr.createProcessor();
                    proc.plateRegionDetectionEnabled = true;
                    proc.cropToPlateRegionEnabled = true;

                    // Use the analyze version that takes the path to a file
                    List<Candidate> cds = proc.analyze(sFilePath);

                    // Output the results
                    Console.WriteLine("***********");
                    Console.WriteLine("Results of IProcessor.analyze(file)");

                    if (cds.Count == 0)
                    {
                        Console.WriteLine("No license plate found");
                    }
                    else
                    {
                        Console.WriteLine("{0} license plate candidates found:", cds.Count);

                        // Iterate over all candidates
                        foreach (Candidate cd in cds)
                        {
                            Console.WriteLine("***********");
                            Console.WriteLine("Light background: {0}, left: {1}, top: {2}, width: {3}, height: {4}", cd.brightBackground, cd.bbox.Left, cd.bbox.Top, cd.bbox.Width, cd.bbox.Height);
                            Console.WriteLine("Plate confidence: {0}. Plate vertices: {1}", cd.plateDetectionConfidence, string.Join(", ", cd.plateRegionVertices));
                            Console.WriteLine("Matches:");

                            // Iterate over all country matches
                            foreach (CountryMatch match in cd.matches)
                            {
                                Console.WriteLine("-----------");
                                Console.WriteLine("Text: {0}, country: {1}, ISO: {2}, confidence: {3}", match.text, match.country, match.countryISO, match.confidence);
                                Console.WriteLine("Elements:");

                                foreach (Element e in match.elements)
                                {
                                    Console.WriteLine("   Glyph: {0}, confidence: {1}, left: {2}, top: {3}, width: {4}, height: {5}",
                                                      e.glyph, e.confidence, e.bbox.Left, e.bbox.Top, e.bbox.Width, e.bbox.Height);
                                }
                            }
                        }
                    }
                }
                else
                {
                    Console.WriteLine("\nUsage:  {0} <country id> <source file> [product key]", Environment.GetCommandLineArgs()[0]);
                    Console.WriteLine("    Parameters:");
                    Console.WriteLine("     country id: Country identifier. The allowed values are");

                    for (uint ui = 0; ui < lpr.numSupportedCountries; ++ui)
                        Console.WriteLine("\t\t\t{0}\t: {1}", ui, lpr.get_countryCode(ui));

                    Console.WriteLine("     source file: file containing the image to be processed");
                    Console.WriteLine("     product key:  product key file. this value is optional, if not provided SimpleLPR will run in evaluation mode");
                }
            }
            catch (System.Exception ex)
            {
                Console.WriteLine("Exception occurred!: {0}", ex.Message);
            }
        }
    }
}