Mstr
This program uses the String Reader module to define a font from an image containing a mosaic of Quebec license plates. Two String Models are then defined and parameterized to read only some valid Quebec license plates. A license plate reading is then performed in a target image of a car on the road.
Language: C#
Functions used: MappAlloc, MappFree, MappTimer, MbufFree, MbufLoad, MbufRestore, MdispAlloc, MdispControl, MdispFree, MdispInquire, MdispSelect, MstrAlloc, MstrAllocResult, MstrControl, MstrDraw, MstrEditFont, MstrFree, MstrGetResult, MstrPreprocess, MstrRead, MstrSetConstraint, MsysAlloc, MsysFree
Categories: Overview, General, Industries, Surveillance/ITS, Applications, ANPR/LPR, Modules, Buffer, Display, Graphics, String Reader, What's New, Older, AIL 10.0 U94
///////////////////////////////////////////////////////////////////////////////
// Aurora Imaging Library
// Filename: MStr.cs
//
// Description: This program uses the String Reader module to define a font
// from an image containing a mosaic of Quebec license plates.
// Two String Models are then defined and parameterized to read
// only some valid Quebec license plates.
// A license plate reading is then performed in a target image
// of a car on the road.
//
// (C) 1992-2026 Zebra Technologies Corp. and/or its affiliates
// All Rights Reserved
///////////////////////////////////////////////////////////////////////////////
using System;
using System.Collections.Generic;
using System.Text;
using Zebra.AuroraImagingLibrary;
namespace MStr
{
class Program
{
// Image file specifications.
private const string IMAGE_FILE_DEFINITION = AIL.M_IMAGE_PATH + "QcPlates.mim";
private const string IMAGE_FILE_TO_READ = AIL.M_IMAGE_PATH + "LicPlate.mim";
// String containing all characters used for font definition.
private const string TEXT_DEFINITION = "AVS300CVK781JNK278 EBX380QKN918HCC839 YRH900ZQR756977AMQ GPK742389EYE569ESQ";
// Font normalization size Y.
private const int NORMALIZATION_SIZE_Y = 20;
// Max size of plate string.
private const int STRING_MAX_SIZE = 32;
static void Main(string[] args)
{
AIL_ID AilApplication = AIL.M_NULL; // Application identifier.
AIL_ID AilSystem = AIL.M_NULL; // System identifier.
AIL_ID AilDisplay = AIL.M_NULL; // Display identifier.
AIL_ID AilImage = AIL.M_NULL; // Image buffer identifier.
AIL_ID AilOverlayImage = AIL.M_NULL; // Overlay image.
AIL_ID AilStrContext = AIL.M_NULL; // String context identifier.
AIL_ID AilStrResult = AIL.M_NULL; // String result buffer identifier.
AIL_INT NumberOfStringRead = 0; // Total number of strings to read.
double Score = 0.0; // String score.
StringBuilder StringResult = new StringBuilder(STRING_MAX_SIZE + 1); // String of characters read.
double Time = 0.0; // Time variable.
// Print module name.
Console.Write("\nSTRING READER MODULE:\n");
Console.Write("---------------------\n\n");
// Allocate defaults
AIL.MappAllocDefault(AIL.M_DEFAULT, ref AilApplication, ref AilSystem, ref AilDisplay, AIL.M_NULL, AIL.M_NULL);
// Restore the font definition image
AIL.MbufRestore(IMAGE_FILE_DEFINITION, AilSystem, ref AilImage);
// Display the image and prepare for overlay annotations.
AIL.MdispSelect(AilDisplay, AilImage);
AIL.MdispControl(AilDisplay, AIL.M_OVERLAY, AIL.M_ENABLE);
AIL.MdispInquire(AilDisplay, AIL.M_OVERLAY_ID, ref AilOverlayImage);
// Allocate a new empty String Reader context.
AIL.MstrAlloc(AilSystem, AIL.M_FONT_BASED, AIL.M_DEFAULT, ref AilStrContext);
// Allocate a new empty String Reader result buffer.
AIL.MstrAllocResult(AilSystem, AIL.M_DEFAULT, ref AilStrResult);
AIL.MstrControl(AilStrContext, AIL.M_CONTEXT, AIL.M_ENCODING, AIL.M_UNICODE);
// Add a new empty user defined font to the context.
AIL.MstrControl(AilStrContext, AIL.M_CONTEXT, AIL.M_FONT_ADD, AIL.M_USER_DEFINED);
// Add user-defined characters from the license plate mosaic image.
// Note that the string that identifies the character values to associate with the
// character representations (TEXT_DEFINITION) includes repeated character values
// (e.g. 'E'); each instance of a repeated character value causes the character
// representation associated with this value to be overwritten.
AIL.MstrEditFont(AilStrContext, AIL.M_FONT_INDEX(0), AIL.M_CHAR_ADD, AIL.M_USER_DEFINED + AIL.M_FOREGROUND_BLACK, AilImage, TEXT_DEFINITION);
// Draw all the characters in the font in the overlay image.
// Note that since M_ORIGINAL is specified, characters are drawn at the location
// from which they were originally extracted from the license plate mosaic image.
// This allows you to see which character representation was used for a repeated
// character value in TEXT_DEFINITION.
AIL.MgraControl(AIL.M_DEFAULT, AIL.M_COLOR, AIL.M_COLOR_GREEN);
AIL.MstrDraw(AIL.M_DEFAULT, AilStrContext, AilOverlayImage, AIL.M_DRAW_CHAR, AIL.M_FONT_INDEX(0), AIL.M_ORIGINAL);
// Normalize the characters of the font to an appropriate size.
AIL.MstrEditFont(AilStrContext, AIL.M_FONT_INDEX(0), AIL.M_CHAR_NORMALIZE, AIL.M_SIZE_Y, NORMALIZATION_SIZE_Y);
// Add 2 new empty strings models to the context for the 2 valid types of
// plates (3 letters followed by 3 numbers or 3 numbers followed by 3 letters)
// Note that the read time increases with the number of strings in the context.
AIL.MstrControl(AilStrContext, AIL.M_CONTEXT, AIL.M_STRING_ADD, AIL.M_USER_DEFINED);
AIL.MstrControl(AilStrContext, AIL.M_CONTEXT, AIL.M_STRING_ADD, AIL.M_USER_DEFINED);
// Set number of strings to read.
AIL.MstrControl(AilStrContext, AIL.M_CONTEXT, AIL.M_STRING_NUMBER, 1);
// Set number of expected characters for all string models to 6 characters.
AIL.MstrControl(AilStrContext, AIL.M_STRING_INDEX(AIL.M_ALL), AIL.M_STRING_SIZE_MIN, 6);
AIL.MstrControl(AilStrContext, AIL.M_STRING_INDEX(AIL.M_ALL), AIL.M_STRING_SIZE_MAX, 6);
// Set default constraint to uppercase letter for all string models
AIL.MstrSetConstraint(AilStrContext, AIL.M_STRING_INDEX(0), AIL.M_DEFAULT, AIL.M_LETTER + AIL.M_UPPERCASE, IntPtr.Zero);
AIL.MstrSetConstraint(AilStrContext, AIL.M_STRING_INDEX(1), AIL.M_DEFAULT, AIL.M_LETTER + AIL.M_UPPERCASE, IntPtr.Zero);
// Set constraint of 3 last characters to digit for the first string model
AIL.MstrSetConstraint(AilStrContext, AIL.M_STRING_INDEX(0), 3, AIL.M_DIGIT, IntPtr.Zero);
AIL.MstrSetConstraint(AilStrContext, AIL.M_STRING_INDEX(0), 4, AIL.M_DIGIT, IntPtr.Zero);
AIL.MstrSetConstraint(AilStrContext, AIL.M_STRING_INDEX(0), 5, AIL.M_DIGIT, IntPtr.Zero);
// Set constraint of 3 first characters to digit for the second string model
AIL.MstrSetConstraint(AilStrContext, AIL.M_STRING_INDEX(1), 0, AIL.M_DIGIT, IntPtr.Zero);
AIL.MstrSetConstraint(AilStrContext, AIL.M_STRING_INDEX(1), 1, AIL.M_DIGIT, IntPtr.Zero);
AIL.MstrSetConstraint(AilStrContext, AIL.M_STRING_INDEX(1), 2, AIL.M_DIGIT, IntPtr.Zero);
// Pause to show the font definition.
Console.Write("This program has defined a font with this Quebec plates mosaic image.\n");
Console.Write("Press any key to continue.\n\n");
Console.ReadKey(true);
// Clear the display overlay.
AIL.MdispControl(AilDisplay, AIL.M_OVERLAY_CLEAR, AIL.M_DEFAULT);
// Load image to read into image buffer.
AIL.MbufLoad(IMAGE_FILE_TO_READ, AilImage);
// Preprocess the String Reader context.
AIL.MstrPreprocess(AilStrContext, AIL.M_DEFAULT);
// Dummy first call for bench measure purpose only (bench stabilization, cache effect, etc...). This first call is NOT required by the application.
AIL.MstrRead(AilStrContext, AilImage, AilStrResult);
// Reset the timer.
AIL.MappTimer(AIL.M_DEFAULT, AIL.M_TIMER_RESET + AIL.M_SYNCHRONOUS, AIL.M_NULL);
// Perform the read operation on the specified target image.
AIL.MstrRead(AilStrContext, AilImage, AilStrResult);
// Read the time.
AIL.MappTimer(AIL.M_DEFAULT, AIL.M_TIMER_READ + AIL.M_SYNCHRONOUS, ref Time);
// Get number of strings read and show the result.
AIL.MstrGetResult(AilStrResult, AIL.M_GENERAL, AIL.M_STRING_NUMBER + AIL.M_TYPE_AIL_INT, ref NumberOfStringRead);
if (NumberOfStringRead >= 1)
{
Console.Write("The license plate was read successfully ({0:#.##} ms)\n\n", Time * 1000);
// Draw read result.
AIL.MgraControl(AIL.M_DEFAULT, AIL.M_COLOR, AIL.M_COLOR_BLUE);
AIL.MstrDraw(AIL.M_DEFAULT, AilStrResult, AilOverlayImage, AIL.M_DRAW_STRING, AIL.M_ALL, AIL.M_DEFAULT);
AIL.MgraControl(AIL.M_DEFAULT, AIL.M_COLOR, AIL.M_COLOR_GREEN);
AIL.MstrDraw(AIL.M_DEFAULT, AilStrResult, AilOverlayImage, AIL.M_DRAW_STRING_BOX, AIL.M_ALL, AIL.M_DEFAULT);
// Print the read result.
Console.Write(" String Score\n");
Console.Write(" -----------------------------------\n");
AIL.MstrGetResult(AilStrResult, 0, AIL.M_STRING, StringResult);
AIL.MstrGetResult(AilStrResult, 0, AIL.M_STRING_SCORE, ref Score);
Console.Write(" {0} {1:0.0}\n", StringResult.ToString(), Score);
}
else
{
Console.Write("Error: Plate was not read.\n");
}
// Pause to show results.
Console.Write("\nPress any key to end.\n\n");
Console.ReadKey(true);
// Free all allocations.
AIL.MstrFree(AilStrContext);
AIL.MstrFree(AilStrResult);
AIL.MbufFree(AilImage);
// Free defaults.
AIL.MappFreeDefault(AilApplication, AilSystem, AilDisplay, AIL.M_NULL, AIL.M_NULL);
}
}
}