Load and display image in Android Studio using OpenCV

Question

I'm trying to load and display an image in Android Studio using OpenCV but it's crash. I don't find where is the problem... Appreciate any helps! Thanks!

public class MainActivity2 extends Activity {

private static final String TAG = "Kate : ";
BaseLoaderCallback mOpenCVCallBack;
Mat mRgba;
ImageView imge1;
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main_activity2);
}


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

public void load_AND_display() {

    //getting ImageView
    imge1= (ImageView) findViewById(R.id.img1);

    try {
        //Loading Image to Mat object
        mRgba= Utils.loadResource(this,R.drawable.mako,Highgui.CV_LOAD_IMAGE_COLOR);
    } catch (IOException e) {
        e.printStackTrace();
    }
    // create a bitmap:
    Bitmap bm = Bitmap.createBitmap(mRgba.cols(), mRgba.rows(),Bitmap.Config.ARGB_8888);
    // convert Mat image to bitmap::
    Utils.matToBitmap(mRgba, bm);
    //setting the image
    imge1.setImageBitmap(bm);
}

@Override
public void onResume() {
    super.onResume();
    mLoaderCallback.onManagerConnected(LoaderCallbackInterface.SUCCESS);
    /*OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_2_4_6, this, mLoaderCallback);*/
}

this is the Logcat:

05-05 15:54:20.323  29948-29948/com.example.myapplication E/art﹕ 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__)
05-05 15:54:20.323  29948-29948/com.example.myapplication E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.example.myapplication, PID: 29948
java.lang.UnsatisfiedLinkError: 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__)

why did you comment the last(correct) line in onResume ? you have to call OpenCVLoader.initAsync() , not mLoaderCallback.onManagerConnected() — berak
– berak, Commented May 5, 2015 at 13:28

DaveL17 · Accepted Answer · 2021-04-21 18:16:58Z

Use the following steps:

Create a loaderCallback variable to check for OpenCv in android studio in the main activty

private val mLoaderCallback: BaseLoaderCallback = object : BaseLoaderCallback(this) {
       override fun onManagerConnected(status: Int) {
           when (status) {
               SUCCESS -> {
                   Log.e("OpenCV", "OpenCV loaded successfully")
               }
               else -> {
                   super.onManagerConnected(status)
               }
           }
       }
   }

In the onResume() of the main activity, check weather OpenCv has been loaded or not:

override fun 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)
    }
}

In the Activity--before calling any opencv operations or initialization Mat--call this:

.....
setContentView(R.layout.activity_main)
OpenCVLoader.initDebug()
 .....

For the image you want to use, convert the bitmap of the image to mat:

val matObject = Mat()
Utils.bitmapToMat(mBitmap, matObject)

Here mBitmap is the bitmap of the image we want to use and Utils.bitmapToMat() is an in-built function of org.opencv.android* In your code, load the drawable as bitmap and then convert to mat.

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