No implementation found for long org.opencv.core.Mat.n_Mat() error Using OpenCV

Question

I am using OpenCV for adaptiveThreshold. My code for image processing using OpenCV is like this:

imageMat=new Mat();
Utils.bitmapToMat(bmp, imageMat);
Imgproc.cvtColor(imageMat, imageMat, Imgproc.COLOR_BGR2GRAY);
Imgproc.GaussianBlur(imageMat, imageMat, new Size(3, 3), 0);
Imgproc.adaptiveThreshold(imageMat, imageMat, 255,Imgproc.ADAPTIVE_THRESH_MEAN_C, Imgproc.THRESH_BINARY_INV, 5, 4);

But I am getting an error while declaring Mat:

No implementation found for long org.opencv.core.Mat.n_Mat() (tried Java_org_opencv_core_Mat_n_1Mat and Java_org_opencv_core_Mat_n_1Mat__)
        at org.opencv.core.Mat.n_Mat(Native Method)
        at org.opencv.core.Mat.<init>(Mat.java:24)
        at com.example.pial_pc.instantbookreview.ImageCapture$3.onPictureTaken(ImageCapture.java:105)

As I'm new to OpenCV, I am not clearly understanding the error. The entire Java class where this code belongs is here.

What should I do to eliminate the error?

Pial Kanti · Accepted Answer · 2016-01-30T08:10:40.007

I have successfully eliminate the error and my app does not crash while executing this line imageMat=new Mat();

The reason for the error is that Android calls the "onCreate" method before loading the OpenCV4Android library.So i have used Async Initialization of OpenCV using OpenCVManager. I have created BaseLoaderCallback before onCreate method. And inside that i have declared new Mat() like this:

private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this) {
    @Override
    public void onManagerConnected(int status) {
        switch (status) {
            case LoaderCallbackInterface.SUCCESS:
            {
                Log.i("OpenCV", "OpenCV loaded successfully");
                imageMat=new Mat();
            } break;
            default:
            {
                super.onManagerConnected(status);
            } break;
        }
    }
};

Then in onResume() i have checked if OpenCV library have been loaded and initialized from within current application package or not. The codes are as follows:

public void onResume()
{
    super.onResume();
    if (!OpenCVLoader.initDebug()) {
        Log.d("OpenCV", "Internal OpenCV library not found. Using OpenCV Manager for initialization");
        OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_3_0_0, this, mLoaderCallback);
    } else {
        Log.d("OpenCV", "OpenCV library found inside package. Using it!");
        mLoaderCallback.onManagerConnected(LoaderCallbackInterface.SUCCESS);
    }
}

And my error is gone. My full updated java class is here.

Reference links :

i'm really in need of help with this question, can you help me, please? https://stackoverflow.com/questions/61216402/how-to-improve-image-segmentation-using-the-watershed — Carlos Diego, Apr 28 '20 at 17:09
InitDebug will always work even in a release build? How do we load/init the library when on release? — Juan Ignacio Avendaño Huergo, Mar 23 '22 at 08:04

score 21 · Answer 2 · edited Oct 25 '19 at 06:58

21

Initialize openCV library in your activity add this code before onCreate() method

static {
    if (!OpenCVLoader.initDebug()) {
        // Handle initialization error
    }
}

add this lib in your project : https://github.com/hschott/Camdroid

edited Oct 25 '19 at 06:58

KlimczakM

12,576
11
64
83

answered Dec 02 '16 at 05:11

user7176550

1,501
14
19

score 15 · Answer 3 · edited Aug 26 '18 at 13:05

15

I put this line on onCreate method and make sure openCvManager is installed. This worked fine for me.

OpenCVLoader.initDebug();

edited Aug 26 '18 at 13:05

Jean-François Corbett

37,420
30
139
188

answered Aug 26 '18 at 12:49

Rikad Fauzi Alawi

177
1
6

Siddharth Bhatheja · Answer 4 · 2018-07-19T12:49:50.617

7

Maybe you are forgetting to include the openCV library.

Include

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

for OpenCV version 3 you should instead add:

static { 
     System.loadLibrary("opencv_java3");
}

Good Luck :)

edited Jul 19 '18 at 12:49

answered Jul 19 '18 at 12:19

Siddharth Bhatheja

376
3
10

This worked with me. Thanks Siddharth Bhatheja! – Zeeshan Qureshi Feb 09 '21 at 01:17
Should I use this code in my activity class ? And what is the equivalent code for Kotlin ? – Abdulsamet Kılınçarslan May 06 '21 at 22:16

score 3 · Answer 5 · answered Jan 08 '20 at 13:51

Use this to resolve error.

public class MainActivity : Activity
    {

        Mat m;
        Mat grayM;
        ImageView imageView;
        public MainActivity()
        {
            if (!OpenCVLoader.InitDebug())
            {
                System.Console.WriteLine("GG");
            }

        }
}

score 1 · Answer 6 · answered Sep 20 '21 at 09:20

This worked for me:

Make sure when linking the module dependency copy the file in native/libs opencv to a jniLibs directory in your project then set the following in your build.gradle(app) the build.

    sourceSets {
        main {
            jni {
                srcDirs 'src/main/jni', 'src/main/jniLibs'
            }
        }
    }

After that add this to your main activity

OpenCVLoader.initDebug()

No implementation found for long org.opencv.core.Mat.n_Mat() error Using OpenCV

6 Answers6

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