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POHow can I print an image on a Bluetooth printer in Android?
 

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  1. POHow can I print an image on a Bluetooth printer in Android?
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    <p>I have to print some data on thermal bluetooth printer, I'm doing with this:</p> <pre><code>String message="abcdef any message 12345"; byte[] send; send = message.getBytes(); mService.write(send); </code></pre> <p>It works well for text, but not for images. I think I need to get the <code>byte[]</code> of the image data. I tried getting the data of the image this way:</p> <pre><code>Bitmap bitmap=BitmapFactory.decodeResource(getResources(), R.drawable.qrcode); ByteArrayOutputStream stream=new ByteArrayOutputStream(); bitmap.compress(Bitmap.CompressFormat.PNG, 90, stream); byte[] image=stream.toByteArray(); </code></pre> <p>Unfortunately the printer prints a lot of strange characters (approx. 50 cm of paper). I don't know how to print the image. </p> <p>I would like to try getting the pixels of the bitmap and next converting it to a <code>byte[]</code> and sending it, but i don't know how to do it. </p> <p>Thanks</p> <p><strong>UPDATE:</strong></p> <p>After so much time, i'm doing this: I have a method called print_image(String file), the which gets the path of the image that i want to print:</p> <pre><code>private void print_image(String file) { File fl = new File(file); if (fl.exists()) { Bitmap bmp = BitmapFactory.decodeFile(file); convertBitmap(bmp); mService.write(PrinterCommands.SET_LINE_SPACING_24); int offset = 0; while (offset &lt; bmp.getHeight()) { mService.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)); } mService.write(slice); } } offset += 24; mService.write(PrinterCommands.FEED_LINE); mService.write(PrinterCommands.FEED_LINE); mService.write(PrinterCommands.FEED_LINE); mService.write(PrinterCommands.FEED_LINE); mService.write(PrinterCommands.FEED_LINE); mService.write(PrinterCommands.FEED_LINE); } mService.write(PrinterCommands.SET_LINE_SPACING_30); } else { Toast.makeText(this, "file doesn't exists", Toast.LENGTH_SHORT) .show(); } } </code></pre> <p>I did it based on this <a href="http://android-essential-devtopics.blogspot.com/2013/02/sending-bit-image-to-epson-printer.html" rel="noreferrer">post</a></p> <p>This is the class PrinterCommands:</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, -128, 0}; 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 is seen in the print_image method I'm calling a method, called convertBitmap, and im sending a bitmap, this is the code:</p> <pre><code> 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()); } } </code></pre> <p>This is the <a href="http://www.rgprt.com/En/Products_show_53.html" rel="noreferrer">printer</a> that i'm using, resolution: 8 dots/mm, 576 dots/line</p> <p>And this is what I like to do (i did it with the same printer, but with an app downloaded from play store) <img src="https://i.stack.imgur.com/pIb37.jpg" alt="Image that I want to print"></p> <p>This is what i'm getting now <img src="https://i.stack.imgur.com/nYoOZ.jpg" alt="My printing trying"></p> <p>Closer: <img src="https://i.stack.imgur.com/PmQop.jpg" alt="A closer part"></p> <p>Closer2: <img src="https://i.stack.imgur.com/cRa98.jpg" alt="enter image description here"></p> <p>A little part of the image can be seen, so I think that i'm closer to can print the image... </p> <p>The image that i'm using is this (576x95):<img src="https://i.stack.imgur.com/DKu6f.png" alt="enter image description here"></p> <p>And this is the converted image (i'm converting it with the upper code): <img src="https://i.stack.imgur.com/oiRVe.png" alt="converted image"></p> <p><img src="https://i.stack.imgur.com/SIz4L.png" alt="Inverted "></p> <p>So, the answer is: what I'm doing wrong?, I think that the error is in this command:</p> <pre><code> public static byte[] SELECT_BIT_IMAGE_MODE = {0x1B, 0x2A, 33, -128, 0}; </code></pre> <p>But, how can I calculate the correct values for my image?, thanks</p>
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    1. COYeah, i send it of the same way that 1st snipplet `mService.write(image)`, the printer has a SDK but it don't compile, so I don't know how to do it.
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      1. POHow can I print an image on a Bluetooth printer in Android?
      1. USLeonardo Sapuy
    2. COIf you have the source for the SDK you can look at how they do it.
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      1. POHow can I print an image on a Bluetooth printer in Android?
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    3. CONow I decompile it, they use a method to return the byte[] array, but it don't works, I implemented that method but when I run the app on the tablet, it dies, generate a force close error... ``
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      1. POHow can I print an image on a Bluetooth printer in Android?
      1. USLeonardo Sapuy
 

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