Mobile license card recognition OCR- combined OpenCV

@Override
public void onManagerConnected(int status) {
super. onManagerConnected(status);
if (status == LoaderCallbackInterface.SUCCESS) {
Log.d(TAG, "OpenCV loaded successfully");
} else {
Log.d (TAG, "OpenCV failed to load");
}
}
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}

@Override
protected void onResume() {
super.onResume();
if (!OpenCVLoader.initDebug()) {
Log.d(TAG, "Internal OpenCV library not found. Using OpenCV Manager for initialization");
OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_3_4_0, getApplicationContext(), mLoaderCallback);
} else {
Log.d(TAG, "OpenCV library found inside package. Using it!");
mLoaderCallback.onManagerConnected(LoaderCallbackInterface.SUCCESS);
}
}
}

When you run the project, you can see that the log is loaded successfully. In fact, if OpenCV is not loaded successfully, a dialog box will prompt you.

Configure NDK, compile library files

Now the latest version of NDK should be r20, you can’t use the latest NDK, otherwise there will be problems with compiling, we go to the official website to download NDK-r14b The author should develop on this version, and attach the download link: NDK download link to download the NDK of the corresponding platform, be sure to download the NDK-r14b version. After configuring the NDK, we create a new jin directory under the main directory, then download the DemoLPR library, and add the include, src, and javaWarpper.cpp in the app/src/main/jni directory inside Copy the files to the jni directory, and copy all the files in the assets/lpr/ directory to the lpr folder in the assets directory of our project. As shown below:

minSdkVersion 19
targetSdkVersion 28
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
ndk {
//Select the corresponding cpu to be added Type of .so library.
abiFilters'armeabi-v7a'
// You can also add'x86','x86_64','mips','mips64'
}

externalNativeBuild {< br /> cmake {
cppFlags "-std=gnu++11"
// Attention! ! ! ! Notice! ! ! ! ! !
//If you are a user developed with Linux, do not change the following line of code. If you are a Win user, please comment the following line of code.
arguments "-DANDROID_TOOLCHAIN=gcc", "-DANDROID_ARM_NEON=TRUE ", "-DANDROID_STL_FORCE_FEATURES=OFF"
}
}
}

externalNativeBuild {
cmake {
path "CMakeLists.txt"< br /> }
}

buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), ' proguard-rules.pro'
}
}
}

dependencies {
implementation fileTree(dir:'libs', include: ['*. jar'])
implementation'com.android.support:appcompat-v7:28.0.0'
implementation'com.android.support.constraint:constraint-layout:1.1.3'
testImplementation'junit:junit:4.12'
androidTestImplementation'com.android.support.test:runner:1.0.2'
androidTestImplementation'com.android .support.test.espresso:espresso-core:3.0.2'
implementation project(path:':openCV')
}

OK, let’s create a new PlateRecognition class under the project And DeepAssetUtil: PlateRecognition:

package com.pcl.lpr.utils;

/**
 * @auther: Aleyn
 * time: 2019/04/24
 */
public class PlateRecognition {

 static {
 System.loadLibrary("lpr");
 }

 static native long InitPlateRecognizer(String casacde_detection,
 String finemapping_prototxt, String finemapping_caffemodel,
 String segmentation_prototxt, String segmentation_caffemodel,
 String charRecognization_proto, String charRecognization_caffemodel,
 String segmentation_free_prototxt, String segmentation_free_caffemodel);

 static native void ReleasePlateRec ognizer(long object);

 public static native String SimpleRecognization(long inputMat, long object);

}

If your package name is the same as mine Not the same, you must go to the javaWartpper.cpp file and modify it to correspond to yours.

DeepAssetUtil:

package com.pcl.lpr.utils;

import android.content.Context;
import android.os.Environment;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class DeepAssetUtil {

 public static final String ApplicationDir = "lpr";
 public static final String CASCADE_FILENAME = "cascade.xml";
 public static final String FINEMAPPING_PROTOTXT = "HorizonalFinemapping.prototxt";
 public static final String FINEMAPPING_CAFFEMODEL = "HorizonalFinemapping.caffemodel";
 public static final String SEGMENTATION_PROTOTXT = "Segmentation.prototxt";
 public static final String SEGMENTATION_CAFFEMODEL = "Segmentation.caffemodel";
 public static final String RECOGNIZATION_PROTOTXT = "CharacterRecognization.prototxt";
 public static final String RECOG NIZATION_CAFFEMODEL = "CharacterRecognization.caffemodel";
 public static final String FREE_INCEPTION_PROTOTXT = "SegmenationFree-Inception.prototxt";
 public static final String FREE_INCEPTION_CAFFEMODEL = "SegmenationFree-Inception.caffemodel";

 /> public static final String SDCARD_DIR = Environment.getExternalStorageDirectory().getAbsolutePath() + File.separator + ApplicationDir; //Decompression file storage location

 private static void CopyAssets(Context context, String assetDir, String dir) {
 String[] files;
 try {
 // How many files are there to get Assets
 files = context.getAssets().list(assetDir);
} catch (IOException e1) {
 return;
 }
 File mWorkingPath = new File(dir);
 // If the file path does not exist
 if ( !mWorkingPath.exists()) {
 // Create a folder
 if (!mWorkingPath.mkdirs()) {
 // Called when the folder is not created successfully
 }< br /> }

 for (String file: files) {
 try {
 // Determine whether it is a folder or a file according to the path
 if (!file.contains(". ")) {
 if (0 == assetDir.length()) {
 CopyAssets(context, file, dir + file + "/");
} else {
 CopyAssets(context, assetDir + "/" + file, dir + "/" + file + "/");
 }
 continue;
 }
 File outFile = new File (mWorkingPath, file);
 if (outFile.exists())
 continue;
 InputStream in;
 if (0 != assetDir.length()) {
 in = context.getAssets().open(assetDir + "/" + file);
} else {
 in = context.getAssets().open(file);
 }< br />
 OutputStream out = new FileOutputStream(ou tFile);
 // Transfer bytes from in to out
 byte[] buf = new byte[1024];
 int len;
 while ((len = in.read( buf))> 0) {
 out.write(buf, 0, len);
 }

 in.close();
 out.close() ;
} catch (IOException e) {
 e.printStackTrace();
 }
 }
 }

 private static void copyFilesFromAssets( Context context) {
 DeepAssetUtil.CopyAssets(context, ApplicationDir, SDCARD_DIR);
 }

 //Initialize recognition resources
 public static long initRecognizer(Context context) { 
 String cascade_filename = SDCARD_DIR + File.separator + CASCADE_FILENAME;
 String finemapping_prototxt = SDCARD_DIR + File.separator + FINEMAPPING_PROTOTXT;
 String finemapping_caffemodel = SDCARD_DIR + File.separator + FINEMAPPLING_CAFFEEM ;
 String segmentation_prototxt = SDCARD_DIR + File.separator + SEGMENTATION_PROTOTXT;
 String segmentation_caffemodel = SDCARD_DIR + File.separator + SEGMENTATION_CAFFEMODEL;
 String character_prototxt = SDCARD_DIR + File.TNIZ; String character_caffemodel = SDCARD_DIR + File.separator + RECOGNIZATION_CAFFEMODEL;
 String segmentation_free_prototxt = SDCARD_DIR + File.separator + FREE_INCEPTION_PROTOTXT;
 String segmentation_free_caffemodel = SDCARD_DIRF + File. 
 //Call JNI to load resource function
 return PlateRecognition.InitPlateRecognizer(
 cascade_filename,
 finemapping_prototxt, finemapping_caffemodel,
 segmentation_prototxt, segmentation_caffemodel,
 character_prototxt, character_caffemodel, 
 segmen tation_free_prototxt, segmentation_free_caffemodel);
 }
}

Okay, now the recognition function is available, there is a difference in recognition interface

Recognition interface:

< p>The recognition interface is actually a camera interface. I just wrote one casually. I also made a recognition box but did not adapt the screen. I originally wanted to post the code in the article, but there is a little bit more, so let’s take a look. Inside the demo. Combine the demo to transplant the recognition function to your project.

Demo operation instructions

Demo address: LPR Open the project will definitely report an error, make the following changes

1. Open with AS Project
2. Set the project NDK to NDK-r14b
3. First modify the CMakeLists.txt file, and modify line 19 to the corresponding path of your local OpenCV SDK.
4. According to your own development platform, set whether to comment on line 23 of build.gradle under the app. After completing the above steps, run the project and there will be no problem.

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That’s it, if you have any questions, please leave a message and more articles. Stay tuned.

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