title: Printing an Image using a Bluetooth Thermal Printer From an Android App?
body: <p><br>I have been trying to get a print of an Image but I have not been successful so far.<br><Br>The printer is a locally manufactured 2" thermal printer having a printing resolution of 8dots/mm, 384dots/line, 203 dpi.<br> The printer is based of a board having the "NXP 2388 ARM v7 Microproc." having a Memory FLASH size of 512 KB, RAM: 128 KB &amp; a Receive Buffer Size of 16KB.
  <br><Br> I followed <a href="https://stackoverflow.com/questions/14530058/how-can-i-print-an-image-on-a-bluetooth-printer-in-android">this question</a> till now.</p>
  
  <p><b>Problem:</b> The image I tried printing is of 576x95 res.
  <img src="https://i.stack.imgur.com/3J2nj.png" alt="enter image description here"></p>
  
  <p>The image got printed(with some error LED lighting up and debug buzzer noise :D) but the orientation of the image was vertical instead of getting horizontally printed; that too at the very left side of the page and the top part of the image was cut-off</p>
  
  <p>Assuming here that I din't passed some of the flags(while making the "packet") compatible with the printer that I have.</p>
  
  <p>I have not worked on bluetooth printing before so any help is appreciable :)</p>
  
  <p>My Existing Main Activity:</p>
  
  <pre><code>public class MainActivity extends Activity 
      {
      // will show the statuses
      TextView myLabel;
      // will enable user to enter any text to be printed
      EditText myTextbox;
      EditText devName;
      public TableLayout tl2; 
      String devid;
      String[] pName;
      String[] LODQTY;
      String[] rte;
      String[] stk;
      String[] oQty;
      String[] oVal;
      String[] fQty;
  
      BitSet dots;
      int mWidth;
      int mHeight;
      String mStatus;
      String TAG = "TAG";
  
      public String msg;
  
      // android built in classes for bluetooth operations
      BluetoothAdapter mBluetoothAdapter;
      BluetoothSocket mmSocket;
      BluetoothDevice mmDevice;
  
      OutputStream mmOutputStream;
      InputStream mmInputStream;
      Thread workerThread;
  
      byte[] readBuffer;
      int readBufferPosition;
      int counter;
      volatile boolean stopWorker;
  
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          devName = (EditText) findViewById(R.id.etdevice);
  
          devName.setText("BTprinter0377");
  
          String[] product_info = new String[6];
          product_info[0] = "CPL400^10^1^0^4^0.4^0";
          product_info[1] = "CPL400^10^1^0^4^0.4^0";
          product_info[2] = "CPL400^10^1^0^4^0.4^0";
          product_info[3] = "CPL400^10^1^0^4^0.4^0";
          product_info[4] = "CPL400^10^1^0^4^0.4^0";
          product_info[5] = "CPL400^10^1^0^4^0.4^0";
  
  
          tl2 = (TableLayout) findViewById(R.id.dynSummary);
          LayoutInflater inflater = getLayoutInflater();
      for (int current = 0; current &lt;= (product_info.length - 1); current++) {
  
  
              final TableRow row = (TableRow)inflater.inflate(R.layout.table_summary_row, tl2 , false);
  
              TextView tv1 = (TextView)row.findViewById(R.id.tvSkuName);
              TextView tv2 = (TextView)row.findViewById(R.id.tvOrderQty);
              TextView tv3 = (TextView)row.findViewById(R.id.tvFreeQty);
  
              TextView tv4 = (TextView)row.findViewById(R.id.tvSampleQty);
              TextView tv5 = (TextView)row.findViewById(R.id.tvTotalOrderKg);
              TextView tv6 = (TextView)row.findViewById(R.id.tvTotalFreeKg);
             TextView tv7 = (TextView)row.findViewById(R.id.tvTotalSampleKg);
  
              StringTokenizer tokens = new StringTokenizer(String.valueOf(product_info[current]), "^");
              //System.out.println("tokens.nextToken().trim()"+tokens.nextToken().trim());
              tv1.setText(tokens.nextToken().trim());
              tv2.setText(tokens.nextToken().trim());
              tv3.setText(tokens.nextToken().trim());
              tv4.setText(tokens.nextToken().trim());
              tv5.setText(tokens.nextToken().trim());
              tv6.setText(tokens.nextToken().trim());
              tv7.setText(tokens.nextToken().trim());
  
              tl2.addView(row);
  
      }
  
          try {
  
              // we have three buttons for specific functions
              Button openButton = (Button) findViewById(R.id.open);
              Button sendButton = (Button) findViewById(R.id.send);
              Button closeButton = (Button) findViewById(R.id.close);
  
              myLabel = (TextView) findViewById(R.id.label);
  
              // open bluetooth connection
              openButton.setOnClickListener(new View.OnClickListener() {
                  public void onClick(View v) {
  
                      devid = devName.getText().toString().trim();
  
                      try {
                          findBT();
                          openBT();
                      } catch (IOException ex) {
                      }
  
                  }
              });
  
              // send data typed by the user to be printed
              sendButton.setOnClickListener(new View.OnClickListener() {
                  public void onClick(View v) {
                      try {
                          sendData();
                      } catch (IOException ex) {
                      }
                  }
              });
  
              // close bluetooth connection
              closeButton.setOnClickListener(new View.OnClickListener() {
                  public void onClick(View v) {
                      try {
                          closeBT();
                      } catch (IOException ex) {
                      }
                  }
              });
  
          } catch (NullPointerException e) {
              e.printStackTrace();
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  
      /*
       * This will find a bluetooth printer device
       */
      void findBT() {
  
          try {
              mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
  
              if (mBluetoothAdapter == null) {
                  myLabel.setText("No bluetooth adapter available");
              }
  
              if (!mBluetoothAdapter.isEnabled()) {
                  Intent enableBluetooth = new Intent(
                          BluetoothAdapter.ACTION_REQUEST_ENABLE);
                  startActivityForResult(enableBluetooth, 0);
              }
  
              Set&lt;BluetoothDevice&gt; pairedDevices = mBluetoothAdapter
                      .getBondedDevices();
              if (pairedDevices.size() &gt; 0) {
                  for (BluetoothDevice device : pairedDevices) {
  
                  System.out.println("device.getName(): "+device.getName().toString());
  
                      if (device.getName().equals("BTprinter0377")) {
                          mmDevice = device;
                          break;
                      }
                  }
              }
              myLabel.setText("Bluetooth Device Found");
          } catch (NullPointerException e) {
              e.printStackTrace();
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  
      /*
       * Tries to open a connection to the bluetooth printer device
       */
      void openBT() throws IOException {
          try {
              // Standard SerialPortService ID
              UUID uuid = UUID.fromString("00001101-0000-1000-8000-00805f9b34fb"); 
  
              mmSocket = mmDevice.createRfcommSocketToServiceRecord(uuid);
              mmSocket.connect();
              mmOutputStream = mmSocket.getOutputStream();
              mmInputStream = mmSocket.getInputStream();
  
              beginListenForData();
  
              myLabel.setText("Bluetooth Opened");
          } catch (NullPointerException e) {
              e.printStackTrace();
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  
      /*
       * After opening a connection to bluetooth printer device, 
       * we have to listen and check if a data were sent to be printed.
       */
      void beginListenForData() {
          try {
              final Handler handler = new Handler();
  
              // This is the ASCII code for a newline character
              final byte delimiter = 10;
  
              stopWorker = false;
              readBufferPosition = 0;
              readBuffer = new byte[1024];
  
              workerThread = new Thread(new Runnable() {
                  public void run() {
                      while (!Thread.currentThread().isInterrupted()
                              &amp;&amp; !stopWorker) {
  
                          try {
  
                              int bytesAvailable = mmInputStream.available();
                              if (bytesAvailable &gt; 0) {
                                  byte[] packetBytes = new byte[bytesAvailable];
                                  mmInputStream.read(packetBytes);
                                  for (int i = 0; i &lt; bytesAvailable; i++) {
                                      byte b = packetBytes[i];
                                      if (b == delimiter) {
                                          byte[] encodedBytes = new byte[readBufferPosition];
                                          System.arraycopy(readBuffer, 0,
                                                  encodedBytes, 0,
                                                  encodedBytes.length);
                                          final String data = new String(
                                                  encodedBytes, "US-ASCII");
                                          readBufferPosition = 0;
  
                                          handler.post(new Runnable() {
                                              public void run() {
                                                  myLabel.setText(data);
                                              }
                                          });
                                      } else {
                                          readBuffer[readBufferPosition++] = b;
                                      }
                                  }
                              }
  
                          } catch (IOException ex) {
                              stopWorker = true;
                          }
  
                      }
                  }
              });
  
              workerThread.start();
          } catch (NullPointerException e) {
              e.printStackTrace();
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  
      /*
       * This will send data to be printed by the bluetooth printer
       */
      void sendData() throws IOException {
          System.out.println("tl2.getChildCount(): "+tl2.getChildCount());
          try {
  
              print_image("/sdcard/tryimg.png");
  
              String msg22;
              msg22 = "\n";
              msg22 += "PN     Or Fr Sa TOKg TFKg TSKg";
              msg22 += "\n";
  
              //mmOutputStream.write(msg22.getBytes());
  
              // tell the user data were sent
              myLabel.setText("Data Sent");
  
          } catch (NullPointerException e) {
              e.printStackTrace();
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  
      /*
       * Close the connection to bluetooth printer.
       */
      void closeBT() throws IOException {
          try {
              stopWorker = true;
              mmOutputStream.close();
              mmInputStream.close();
              mmSocket.close();
              myLabel.setText("Bluetooth Closed");
          } catch (NullPointerException e) {
              e.printStackTrace();
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  
  
      public String convertBitmap(Bitmap inputBitmap) {
  
          mWidth = inputBitmap.getWidth();
          mHeight = inputBitmap.getHeight();
  
          convertArgbToGrayscale(inputBitmap, mWidth, mHeight);
          mStatus = "ok";
          return mStatus;
  
      }
  
      private void convertArgbToGrayscale(Bitmap bmpOriginal, int width,
              int height) {
          int pixel;
          int k = 0;
          int B = 0, G = 0, R = 0;
           dots = new BitSet();
          try {
  
              for (int x = 0; x &lt; height; x++) {
                  for (int y = 0; y &lt; width; y++) {
                      // get one pixel color
                      pixel = bmpOriginal.getPixel(y, x);
  
                      // retrieve color of all channels
                      R = Color.red(pixel);
                      G = Color.green(pixel);
                      B = Color.blue(pixel);
                      // take conversion up to one single value by calculating
                      // pixel intensity.
                      R = G = B = (int) (0.299 * R + 0.587 * G + 0.114 * B);
                      // set bit into bitset, by calculating the pixel's luma
                      if (R &lt; 55) {                       
                          dots.set(k);//this is the bitset that i'm printing
                      }
                      k++;
  
                  }
  
  
              }
  
  
          } catch (Exception e) {
              // TODO: handle exception
              Log.e(TAG, e.toString());
          }
      }
  
  
      private void print_image(String file) throws IOException {
          File fl = new File(file);
          if (fl.exists()) {
              Bitmap bmp = BitmapFactory.decodeFile(file);
              convertBitmap(bmp);
              mmOutputStream.write(PrinterCommands.SET_LINE_SPACING_24);
  
              int offset = 0;
              while (offset &lt; bmp.getHeight()) {
                  mmOutputStream.write(PrinterCommands.SELECT_BIT_IMAGE_MODE);
                  for (int x = 0; x &lt; bmp.getWidth(); ++x) {
  
                      for (int k = 0; k &lt; 3; ++k) {
  
                          byte slice = 0;
                          for (int b = 0; b &lt; 8; ++b) {
                              int y = (((offset / 8) + k) * 8) + b;
                              int i = (y * bmp.getWidth()) + x;
                              boolean v = false;
                              if (i &lt; dots.length()) {
                                  v = dots.get(i);
                              }
                              slice |= (byte) ((v ? 1 : 0) &lt;&lt; (7 - b));
                          }
                          mmOutputStream.write(slice);
                      }
                  }
                  offset += 24;
                  mmOutputStream.write(PrinterCommands.FEED_LINE);
                  mmOutputStream.write(PrinterCommands.FEED_LINE);          
                  mmOutputStream.write(PrinterCommands.FEED_LINE);
                  mmOutputStream.write(PrinterCommands.FEED_LINE);
                  mmOutputStream.write(PrinterCommands.FEED_LINE);
                  mmOutputStream.write(PrinterCommands.FEED_LINE);
              }
              mmOutputStream.write(PrinterCommands.SET_LINE_SPACING_30);
  
  
          } else {
              Toast.makeText(this, "file doesn't exists", Toast.LENGTH_SHORT).show();
          }
      }
  
  }
  </code></pre>
  
  <p>The PrinterCommands Class:</p>
  
  <pre><code>public class PrinterCommands {
  public static final byte[] INIT = {27, 64};
  public static byte[] FEED_LINE = {10};
  
  public static byte[] SELECT_FONT_A = {27, 33, 0};
  
  public static byte[] SET_BAR_CODE_HEIGHT = {29, 104, 100};
  public static byte[] PRINT_BAR_CODE_1 = {29, 107, 2};
  public static byte[] SEND_NULL_BYTE = {0x00};
  
  public static byte[] SELECT_PRINT_SHEET = {0x1B, 0x63, 0x30, 0x02};
  public static byte[] FEED_PAPER_AND_CUT = {0x1D, 0x56, 66, 0x00};
  
  public static byte[] SELECT_CYRILLIC_CHARACTER_CODE_TABLE = {0x1B, 0x74, 0x11};
  
  public static byte[] SELECT_BIT_IMAGE_MODE = {0x1B, 0x2A, 33, (byte) 255, 3};
  //public static byte[] SELECT_BIT_IMAGE_MODE = {0x1B, 0x2A, 0x64, 0x63, 48, (byte) 255};
  
  public static byte[] SET_LINE_SPACING_24 = {0x1B, 0x33, 24};
  public static byte[] SET_LINE_SPACING_30 = {0x1B, 0x33, 30};
  
  public static byte[] TRANSMIT_DLE_PRINTER_STATUS = {0x10, 0x04, 0x01};
  public static byte[] TRANSMIT_DLE_OFFLINE_PRINTER_STATUS = {0x10, 0x04, 0x02};
  public static byte[] TRANSMIT_DLE_ERROR_STATUS = {0x10, 0x04, 0x03};
  public static byte[] TRANSMIT_DLE_ROLL_PAPER_SENSOR_STATUS = {0x10, 0x04, 0x04};
  }
  </code></pre>
  
  <p>As mentioned in the dev manual of the printer(pdf):<br></p>
  
  <pre><code>Bit Map Image Print
  1. Select the image either from PC or from mobile's SD card.
  2. Convert the image into monochrome bmp.
  3. Resize the image to fit into the printer paper area if it is exceeding
  4. Now read the processed image through fileinputstream and save it into byte array.
  5. Make the packet of image and then send it to printer over outputstream.
  </code></pre>
  
  <p>The required packet structure:
  <img src="https://i.stack.imgur.com/qaGgS.png" alt="enter image description here">
  <br><Br>
   The packet fields chart:
  <img src="https://i.stack.imgur.com/JPbY5.png" alt="enter image description here">
  <br><br></p>
  
  <p>Alignment table &amp; other info:
  <img src="https://i.stack.imgur.com/nFXDo.png" alt="enter image description here">
  <br><Br></p>