Sren-Hmkn

<!--

    <uses-permission android:name="android.permission.CAMERA" /> 
Add the following two lines below the line above -->
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

<!-- ... -->

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// public class CameraActivity extends AppCompatActivity implements CameraBridgeViewBase.CvCameraViewListener {...
//
//  define a constant of the needed subfolder
    public static final String TESS_DATA = "/tessdata";
//
//  private static final String TAG = "CameraActivity";
//...
//  protected void onCreate(Bundle savedInstanceState) {...
//...
//     Call method in onCreate before you create a MyTessOCR instance

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//...
//...
//...
//       Mat usedMat;
         MyTessOCR mTessOCR;
         Bitmap bitmap;
//
//       BaseLoaderCallback mLoaderCallBack = new BaseLoaderCallback(this){...}
//...
//...

Sren-Hmkn

package com.example.android.myapplication;

import android.content.Context;
import android.graphics.Bitmap;

import com.googlecode.tesseract.android.TessBaseAPI;

import static com.googlecode.tesseract.android.TessBaseAPI.PageSegMode.PSM_AUTO;

public final class MyTessOCR {

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// ...
// ...
//    JavaCameraView javaCameraView;
//    Button makeNormal, makeGray, makeCanny, makeDilate, makeErode;
  
    Button makeRead;
    TextView readTextView;
    Bitmap bitmap;
  
//    Mat usedMat;

Sren-Hmkn

// include your header file here!
#include <com_example_android_myapplication_OpenCvMaker.h>

// change the name of this according to the methods name in your header, mine looks like this:
JNIEXPORT jint JNICALL Java_com_example_android_myapplication_OpenCvMaker_makeGray
  (JNIEnv *, jclass, jlong addrInput, jlong addrOutput){
  return (jint) toGray((*(Mat*) addrInput),(*(Mat*) addrOutput));
  }

  int toGray(Mat img, Mat& gray) {

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//...#include <jni.h>

#include <opencv2/opencv.hpp>
#include <stdio.h>

using namespace cv;
using namespace std;
// ...
// extern "C" {
// #endif

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// change the package name to yours here
package com.example.android.opencvdemo;

public class OpenCvMaker {

    private static boolean canny;
    private static boolean dilate;
    private static boolean erode;
    private static boolean gray;
    private static boolean normal;

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//...
//    JavaCameraView javaCameraView;
//    Mat usedMat;

      Button makeNormal, makeGray, makeCanny, makeDilate, makeErode;

//...
// BaseLoaderCallback mLoaderCallBack = new BaseLoaderCallback(this){}
//...

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    protected void deliverAndDrawFrame(CvCameraViewFrame frame) {
        Mat modified;

        if (mListener != null) {
            modified = mListener.onCameraFrame(frame);
        } else {
            modified = frame.rgba();
        }