安卓OCR扫描问题

Question

安卓OCR扫描问题

3

我正在尝试使用tessract/tess-two库创建一个带有OCR扫描仪的应用程序，我已经成功地访问了手机相机，我可以手动对焦，但当我拍照时会出现以下错误：

07-18 19:07:06.335 2585-2585/com.fastnetserv.myapp D/DBG_com.fastnetserv.myapp.MainActivity: Picture taken
07-18 19:07:06.335 2585-2585/com.fastnetserv.myapp D/DBG_com.fastnetserv.myapp.MainActivity: Got null data
07-18 19:07:06.405 2585-2585/com.fastnetserv.myapp D/DBG_com.fastnetserv.myapp.MainActivity: Picture taken
07-18 19:07:06.426 2585-2585/com.fastnetserv.myapp D/DBG_com.fastnetserv.myapp.MainActivity: Got bitmap
07-18 19:07:06.427 2585-11599/com.fastnetserv.myapp E/DBG_com.fastnetserv.myapp.TessAsyncEngine: Error passing parameter to execute(context, bitmap)
07-18 19:07:14.111 2585-2585/com.fastnetserv.myapp D/DBG_com.fastnetserv.myapp.CameraUtils: CameraEngine Stopped

以下是CameraFragment的代码：

package com.fastnetserv.myapp;

import android.content.Context;
import android.graphics.Bitmap;
import android.hardware.Camera;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

import com.googlecode.tesseract.android.TessBaseAPI;


/**
 * A simple {@link Fragment} subclass.
 * Activities that contain this fragment must implement the
 * {@link //CameraFragment.//OnFragmentInteractionListener} interface
 * to handle interaction events.
 * Use the {@link CameraFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class CameraFragment extends Fragment implements SurfaceHolder.Callback, View.OnClickListener,
        Camera.PictureCallback, Camera.ShutterCallback {

    static final String TAG = "DBG_" + MainActivity.class.getName();

    Button shutterButton;
    Button focusButton;
    FocusBoxView focusBox;
    SurfaceView cameraFrame;
    CameraEngine cameraEngine;

    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    private OnFragmentInteractionListener mListener;

    public CameraFragment() {
        // Required empty public constructor
    }

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment CameraFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static CameraFragment newInstance(String param1, String param2) {
        CameraFragment fragment = new CameraFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_camera, container, false);
    }

    // TODO: Rename method, update argument and hook method into UI event
    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        try {
            mListener = (OnFragmentInteractionListener) context;
        } catch (ClassCastException e) {
            throw new ClassCastException(context.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }

    // Camera Code

    public String detectText(Bitmap bitmap) {

        TessDataManager.initTessTrainedData(getActivity());
        TessBaseAPI tessBaseAPI = new TessBaseAPI();

        String path = "/mnt/sdcard/com.fastnetserv.myapp/tessdata/ita.traineddata";

        Log.d(TAG, "Check data path: " + path);

        tessBaseAPI.setDebug(true);
        tessBaseAPI.init(path, "ita"); //Init the Tess with the trained data file, with english language

        //For example if we want to only detect numbers
        tessBaseAPI.setVariable(TessBaseAPI.VAR_CHAR_WHITELIST, "1234567890");
        tessBaseAPI.setVariable(TessBaseAPI.VAR_CHAR_BLACKLIST, "!@#$%^&*()_+=-qwertyuiop[]}{POIU" +
                "YTREWQasdASDfghFGHjklJKLl;L:'\"\\|~`xcvXCVbnmBNM,./<>?");


        tessBaseAPI.setImage(bitmap);

        String text = tessBaseAPI.getUTF8Text();

        //Log.d(TAG, "Got data: " + result);
        tessBaseAPI.end();

        return text;
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {

        Log.d(TAG, "Surface Created - starting camera");

        if (cameraEngine != null && !cameraEngine.isOn()) {
            cameraEngine.start();
        }

        if (cameraEngine != null && cameraEngine.isOn()) {
            Log.d(TAG, "Camera engine already on");
            return;
        }

        cameraEngine = CameraEngine.New(holder);
        cameraEngine.start();

        Log.d(TAG, "Camera engine started");
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {

    }


    @Override
    public void onResume() {
        super.onResume();

        cameraFrame = (SurfaceView) getActivity().findViewById(R.id.camera_frame);
        shutterButton = (Button) getActivity().findViewById(R.id.shutter_button);
        focusBox = (FocusBoxView) getActivity().findViewById(R.id.focus_box);
        focusButton = (Button) getActivity().findViewById(R.id.focus_button);

        shutterButton.setOnClickListener(this);
        focusButton.setOnClickListener(this);

        SurfaceHolder surfaceHolder = cameraFrame.getHolder();
        surfaceHolder.addCallback(this);
        surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

        cameraFrame.setOnClickListener(this);
    }

    @Override
    public void onPause() {
        super.onPause();

        if (cameraEngine != null && cameraEngine.isOn()) {
            cameraEngine.stop();
        }

        SurfaceHolder surfaceHolder = cameraFrame.getHolder();
        surfaceHolder.removeCallback(this);
    }

    @Override
    public void onClick(View v) {
        if(v == shutterButton){
            if(cameraEngine != null && cameraEngine.isOn()){
                cameraEngine.takeShot(this, this, this);
            }
        }

        if(v == focusButton){
            if(cameraEngine!=null && cameraEngine.isOn()){
                cameraEngine.requestFocus();
            }
        }
    }

    @Override
    public void onPictureTaken(byte[] data, Camera camera) {

        Log.d(TAG, "Picture taken");

        if (data == null) {
            Log.d(TAG, "Got null data");
            return;
        }

        Bitmap bmp = Tools.getFocusedBitmap(getActivity(), camera, data, focusBox.getBox());

        Log.d(TAG, "Got bitmap");

        new TessAsyncEngine().executeOnExecutor(AsyncTask.SERIAL_EXECUTOR, this, bmp);

    }

    @Override
    public void onShutter() {

    }

}

这里是TessAsyncEngine：

package com.fastnetserv.myapp;

import android.app.Activity;
import android.graphics.Bitmap;
import android.os.AsyncTask;
import android.util.Log;

import com.fastnetserv.myapp.ImageDialog;
import com.fastnetserv.myapp.Tools;

/**
 * Created by Fadi on 6/11/2014.
 */
public class TessAsyncEngine extends AsyncTask<Object, Void, String> {

    static final String TAG = "DBG_" + TessAsyncEngine.class.getName();

    private Bitmap bmp;

    private Activity context;


    @Override
    protected String doInBackground(Object... params) {

        try {

            if(params.length < 2) {
                Log.e(TAG, "Error passing parameter to execute - missing params");
                return null;
            }

            if(!(params[0] instanceof Activity) || !(params[1] instanceof Bitmap)) {
                Log.e(TAG, "Error passing parameter to execute(context, bitmap)");

                return null;
            }

            context = (Activity)params[0];

            bmp = (Bitmap)params[1];

            if(context == null || bmp == null) {
                Log.e(TAG, "Error passed null parameter to execute(context, bitmap)");
                return null;
            }

            int rotate = 0;

            if(params.length == 3 && params[2]!= null && params[2] instanceof Integer){
                rotate = (Integer) params[2];
            }

            if(rotate >= -180 && rotate <= 180 && rotate != 0)
            {
                bmp = Tools.preRotateBitmap(bmp, rotate);
                Log.d(TAG, "Rotated OCR bitmap " + rotate + " degrees");
            }

            TessEngine tessEngine =  TessEngine.Generate(context);

            bmp = bmp.copy(Bitmap.Config.ARGB_8888, true);

            String result = tessEngine.detectText(bmp);

            Log.d(TAG, result);

            return result;

        } catch (Exception ex) {
            Log.d(TAG, "Error: " + ex + "\n" + ex.getMessage());
        }

        return null;
    }

    @Override
    protected void onPostExecute(String s) {

        if(s == null || bmp == null || context == null)
            return;

        ImageDialog.New()
                .addBitmap(bmp)
                .addTitle(s)
                .show(context.getFragmentManager(), TAG);

        super.onPostExecute(s);
    }
}

我遵循了这个教程（http://www.codeproject.com/Tips/840623/Android-Character-Recognition），但由于我对Android的知识不足，可能忘记了某些内容。

- DarkVex

不要将this传递到executeOnExecutor中，而是尝试使用getActivity()，因为你在一个片段中。但是，Ped7g所说的是正确的，你也可以将你的异步任务作为CameraFragment的内部类，这样它就可以在onPreExecute和onPostExecute中访问相同的上下文。 - Jon

我也会尝试你的建议，谢谢Jonathan！ - DarkVex

1个回答

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- Ped7g · Accepted Answer

那个if(context == null || bmp == null)是不必要的，因为你已经用instanceof测试了这些值。

但我猜你的主要问题是从Fragment传递this作为Activity参数，而它并不是。

为了解决这个问题..我总体上会尽量避免在android上随意传递Activity指针，因为它们的生命周期非常有限。我有一个使用tess-two的应用程序，我不记得需要Activity来初始化它（尽管通常我从本地C++中初始化它，所以YMMV）。

那个调用只需要Context，不是吗？如果是的话，我建议改为使用getApplicationContext()值。我认为这也可以直接或间接地从Fragment中访问。

很抱歉没有尝试你的代码，但这是你可以很容易地调试的问题。

关于Android和Tesseract的使用，还有一个需要注意的问题。什么是Tools.getFocusedBitmap？它会合理地裁剪图片吗？如果它保持全尺寸，并且您的相机设置为全尺寸，则会在Android中立即触发内存不足（OOM）错误，因为您正在处理5-10+MP的位图。要么将相机设置为合理的低分辨率，要么尽快剪切照片的设计部分并放弃整个图像，最好作为处理的第一步。

您可能需要重新考虑整个tess-two事情，并尝试来自Google Play服务的官方Google Text API。

https://developers.google.com/android/reference/com/google/android/gms/vision/text/Text

这是全新的添加内容，我猜它将使用第二代Tesseract引擎和最新改进，因此很可能会获得比tess-two更好的结果和速度。

我认为它只能从Android 4.4及具有Google Play服务的设备中访问，并且跨平台性不好，因此我在我的项目中仍然使用tess-two - 因为我还必须支持iOS和Windows Phone。

总的来说，我不相信那些没有源代码的东西，没有源代码的软件就像僵尸一样，在你使用它时已经死了（最多需要30-50年才会死亡），而且这浪费了那些程序员的时间和技能。