HI, help me please.

[Rik-son]

Hi. Greetings from Slovakia. Your code looks well done. I found it because I'm lost in a problem with my application. I have an application for searching and managing BT thermal printers. I print a PNG image through it, but my printing is too slow (15-20 seconds) and it's in parts (for example, 1/5 is printed then a pause, another 1/5, pause....) when I put the same image in your application, it prints it in one go, in one piece, without any interruptions and quickly. which is great.

I would like to ask for your advice, how do you do it? how can I do it better?

thank you

[anastaciocintra]

hi @Rik-TRIFY ,
in my understanding, you are building one application, probably android, that send data to the printer, and, this data are usually in image format. Am i right?
In this case, the pattern of image jpg or any other pattern (tiff, png, etc) shoudn't send directly to the esc/pos printer. Basicly you need to slice your image and send "line-by-line". The escpos-coffee have one interface ImageWrapperInterface and three implementation: RasterBitImageWrapper, GraphicsImageWrapper and BitImageWrapper, you can shose one bitonal algorithm (BitonalOrderedDither) is my preferred. And it this is all.
take a look at https://github.com/anastaciocintra/escpos-coffee/wiki/Images

[Rik-son]

Hello. Thanks for the answer.
Yes, exactly, an android application. I have an application that searches for and pairs a printer.
The application receives the image and processes it. Then it cuts it and sends it to the printer in chunks. but it is very slow in my case, and it prints a chunk then waits, again a chunk and waits again. Through other applications (rawBT and the like) it prints much faster and without stopping.

I don't know what I'm doing wrong. I also consulted chatgpt. Currently it works through GS in 0.

I'm trying to print plain text for a diacritics test, but even that fails through the classic ESC and prints strange characters.

Could you please guide me how to do it correctly?

Here is the code for plain text:

/// Tlač textovej úlohy priamo ako UTF-8 text (pôvodná funkčná verzia)
Future _printTextJob(
PrintJob job,
fbp.BluetoothDevice device,
Duration delay,
) async {
final text = utf8.decode(job.data);
_logService.log(
LogLevel.info,
LogCategory.print,
'Tlač textu s ESC t 18 (CP852 Latin-2): ${text.substring(0, text.length > 50 ? 50 : text.length)}...',
);

// ESC/POS príkazy s nastavením character code table
final List<int> printData = [];

// Inicializácia tlačiarne
printData.add(0x1B); // ESC
printData.add(0x40); // @ (reset tlačiarne)

// Nastavenie character code table na 18 (CP852 Latin-2 pre slovenské znaky)
printData.add(0x1B); // ESC
printData.add(0x74); // t (select character code table command)
printData.add(18); // 18 = CP852_Latin2 (pre slovenské diakritické znaky)

// Pridanie už enkódovaných UTF-8 bajtov z job.data
printData.addAll(job.data);

// Nový riadok a posun papiera
printData.add(0x0A); // LF
printData.add(0x0D); // CR

final Uint8List textData = Uint8List.fromList(printData);

// Rozdelenie na chunky pre Bluetooth
const int maxChunkSize = 150;
final chunks = <Uint8List>[];

for (int i = 0; i < textData.length; i += maxChunkSize) {
  final end = (i + maxChunkSize < textData.length) ? i + maxChunkSize : textData.length;
  chunks.add(textData.sublist(i, end));
}

await _sendChunkedData(job, device, chunks, delay);

}

it should print:

// Vytvorenie testovacieho obsahu s diakritikou - nový správny text
final String testContent = '''
Ľ Š Č Ť Ž Ý Á Í É Ú Ä Ň Ô Ď € a ľ š č ť ž ý á í é ä ú ň ô ď

text malým písmom a TEXT VELKÝM PÍSMOM
''';

I am also attaching the entire file. There is also the print version of the image. But I don't know if it will tell you anything and if you will be able to advise me.

print.txt

[anastaciocintra]

hi, @Rik-TRIFY
unfortunately I don't have sample in flutter, I have only sample in android java. U can see it at https://github.com/anastaciocintra/escpos-coffee-samples/tree/master/miscellaneous/AndroidImage.
Maybe it is necessary: build one lib in java and then, call it inside flutter app.