title: Tesseract ocr returns null string
body: <p>I am building an OCR app for android and i use tesseract ocr engine. Somehow every time i use the engine on a photo it returns an empty text.
  This is my code:</p>
  
  <pre><code>public String detectText(Bitmap bitmap) {
      TessBaseAPI tessBaseAPI = new TessBaseAPI();
      String mDataDir = setTessData();
      tessBaseAPI.setDebug(true);
      tessBaseAPI.init(mDataDir + File.separator, "eng");
      tessBaseAPI.setImage(bitmap);
      tessBaseAPI.setPageSegMode(TessBaseAPI.OEM_TESSERACT_ONLY);
      String text = tessBaseAPI.getUTF8Text();
  
      tessBaseAPI.end();
  
      return text;
  }
  
  private String setTessData(){
      String mDataDir = this.getExternalFilesDir("data").getAbsolutePath();
      String mTrainedDataPath = mDataDir + File.separator + "tessdata";
      String mLang = "eng";
      // Checking if language file already exist inside data folder
      File dir = new File(mTrainedDataPath);
      if (!dir.exists()) {
          if (!dir.mkdirs()) {
              //showDialogFragment(SD_ERR_DIALOG, "sd_err_dialog");
          } else {
          }
      }
  
      if (!(new File(mTrainedDataPath + File.separator + mLang + ".traineddata")).exists()) {
  
          // If English or Hebrew, we just copy the file from assets
          if (mLang.equals("eng") || mLang.equals("heb")){
              try {
                  AssetManager assetManager = context.getAssets();
                  InputStream in = assetManager.open(mLang + ".traineddata");
                  OutputStream out = new FileOutputStream(mTrainedDataPath + File.separator + mLang + ".traineddata");
                  copyFile(in, out);
                  //Toast.makeText(context, getString(R.string.selected_language) + " " + mLangArray[mLangID], Toast.LENGTH_SHORT).show();
                  //Log.v(TAG, "Copied " + mLang + " traineddata");
              } catch (IOException e) {
                  //showDialogFragment(SD_ERR_DIALOG, "sd_err_dialog");
              }
          }
  
          else{
  
              // Checking if Network is available
              if (!isNetworkAvailable(this)){
                  //showDialogFragment(NETWORK_ERR_DIALOG, "network_err_dialog");
              }
              else {
                  // Shows a dialog with File dimension. When user click on OK download starts. If he press Cancel revert to english language (like NETWORK ERROR)
                  //showDialogFragment(CONTINUE_DIALOG, "continue_dialog");
              }
          }
      }
      else {
          //Toast.makeText(mThis, getString(R.string.selected_language) + " " + mLangArray[mLangID], Toast.LENGTH_SHORT).show();
      }
      return mDataDir;
  }
  </code></pre>
  
  <p>I have debugged it many times and the bitmap is being transferred correctly to the detectText method. The language data files(tessdata) exists on the phone and the path to them is also correct.</p>
  
  <p>Does anybody knows what the problem here?</p>