How can I print an image with Esc Pos with Android (Java)

Question

I have an app that can print tickets with Thermal Printers using ESC POS language. The code I'm using right now is:

       /* <-40char-> */
                    Socket sock = new Socket(Impresora.getImpresora_Tickets().getIp(), Impresora.getImpresora_Tickets().getPuerto());
                    OutputStreamWriter osw = new OutputStreamWriter(sock.getOutputStream(), Charset.forName("CP1252"));
                    PrintWriter oStream = new PrintWriter(osw);

       /*Start*/
                    for(int i = 0; i<Impresora.getImpresora_Tickets().getInic().size(); i++)
                        oStream.print(Impresora.getImpresora_Tickets().getInic().get(i));

       /*Set Font Size*/
                    for(int i = 0; i<Impresora.getImpresora_Tickets().getLetra4().size(); i++)
                            oStream.print(Impresora.getImpresora_Tickets().getLetra4().get(i));

       oStream.println("HELLO WORLD");

And it works fine. The thing is that now I'm capturing the user's signature with the tablet and I want to print it in the end of the ticket. I have it as a bitmap object but I don't know how to send it to the printer. Can someone help me? Thanks!

EDIT 1:

I'm trying to do something but I think I'm not going in the right way...

/**
* Redimensionar imagen
*/
Bitmap firma = Current_Mesa.getT().getFirma_credito();
firma = Bitmap.createScaledBitmap(firma, 255, 64, false);

/**
* Print imagen
*/
ByteArrayOutputStream stream = new ByteArrayOutputStream();
firma.compress(CompressFormat.JPEG, 70, stream);
byte[] firma_bytes = stream.toByteArray();

byte[] SELECT_BIT_IMAGE_MODE = {0x1B, 0x2A, 33};
byte[] SET_LINE_SPACE_24 = {0x1B, 0x33, 24};
byte[] PRINT_AND_FEED_PAPER = new byte[]{0x0A};

for(byte b : SELECT_BIT_IMAGE_MODE)
oStream.print((char)b);

for(byte b : SET_LINE_SPACE_24)
oStream.print((char)b);

for(int i = 0; i < firma_bytes.length; i+=8)
{
    for(int plus = 0; plus < 8; plus++)
    oStream.print(firma_bytes[i+plus]);

    for(byte b : PRINT_AND_FEED_PAPER)
        oStream.print((char)b);
}

Is it a question about the ESC POS protocol, or about Java specifically? — Stack Exchange Broke The Law
– Stack Exchange Broke The Law, Commented Jun 23, 2015 at 12:01
It's about ESC POS, but if I can get a sample of how to do it in Java, it will be awesome. — Óscar
– Óscar, Commented Jun 23, 2015 at 12:55

Elemental · Accepted Answer · 2015-06-23 14:20:59Z

1

I have completed this task before in c++ and it isn't trivial. You need to get pixel by pixel access to the image (which should be easy if you have a bitmap).

Then you have to divide the image into 8 pixel horizontal bands and get a character representing each column of eight pixels (using a bitwise or). The POS documentation should tell you how to print a single row of graphics using this method.

None of this is very hard but it took a bit of fiddling to get it perfect for all image sizes and shapes.

A more detailed description: The printer can print images left to right in 8 pixel vertical bands, that means it first print the top 8 pixels of the image - then scrolls the paper and prints the next 8 pixel row. So you do it like this:

Go down the image starting at the top and divide it into 8 pixel high bands.For each band:

Send the ESC POS sequence that puts the printer into 'graphics mode'. Loop through the image band left to right. For each column of 8 pixels in the band:

Work out the bit values of the pixels top to bottom. Convert this to a simple byte values like so IsPixelBlack(0)*1+IsPixelBlack(1)*2+IsPixelBlack(2)*4+...+IsPixelBlack(7)*128 where IsPixelBlack(x) is 1 if the x pixel in the column is black or 0 otherwise. Then send this byte value to the printer as a character.

So you end up sending one character for every 8 pixel column expressed as string of one band of data to be printed.

Also I thought Epson had an android SDK for ESC/POS devices; I've never used it but thought it was free to use.

edited Jun 23, 2015 at 14:20

answered Jun 23, 2015 at 12:11

Elemental

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3 Comments

Óscar Over a year ago

It's easy to get pixel by pixel access, but I'm not sure about how to divide the image into 8 pixel horizontal bands. I'm not sure about how esc pos words for printing images... each band is a row? A row can be created with multiple bands? If u can help me with your c++ code I'll be really happy.

Elemental Over a year ago

Unfortunately this code is not public and so I can't paste it here but I will add a more complete description of what I mean.

Óscar Over a year ago

Hi Elemental, I'm trying to do what u told me but I'm pretty newbie with ESC POS and I'm lost. I'm trying to do something with this code: stackoverflow.com/questions/14099239/… but I'm not sure about how to divide the Bitmap in pixels. I have it in a Byte array but I don't know how to continue...

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