thermal_unicode_print: Print Bangla, Arabic & Unicode Text on Thermal Printers in Flutter

Most ESC/POS thermal printers only understand a limited set of built-in character sets, which makes printing Bangla, Arabic, Devanagari, or other Unicode scripts a real headache. The common workaround — screenshotting an entire widget tree and printing it as one giant image — burns memory fast and gets worse as receipts grow longer. The thermal_unicode_print package solves this by rendering Unicode text one bounded line or row at a time, so output size never grows with receipt length.

Why thermal_unicode_print?

Thermal printers used in POS systems across Bangladesh, the Middle East, and South Asia rarely ship with proper Unicode fonts. Rendering a full receipt as a single bitmap works for short receipts, but memory usage balloons on longer ones. This package renders each line or row independently as a small, bounded bitmap and streams it straight into an esc_pos_utils_plus Generator, keeping memory usage flat regardless of receipt length.

Key Features

• Prints any Unicode script — Bangla, Arabic, Devanagari, and more — on ESC/POS compatible printers
• Memory-efficient line-by-line rendering instead of whole-receipt screenshots
• Tabular rows with flexible, configurable column widths
• PNG preview variants so you can develop and test without physical hardware
• Integrates directly with the esc_pos_utils_plus Generator API

Installation

Add the package to your pubspec.yaml:

dependencies:
  thermal_unicode_print: ^0.0.1
  esc_pos_utils_plus: ^2.0.4

Then run:

flutter pub get

Getting Started

Render a single line of Unicode text and feed it into your ESC/POS generator:

import 'package:thermal_unicode_print/thermal_unicode_print.dart';
import 'package:esc_pos_utils_plus/esc_pos_utils_plus.dart';

Future<void> printReceiptHeader(Generator generator) async {
  final line = await UnicodeLinePrinter.renderLine(
    text: 'পণ্যের তালিকা',
    fontSize: 28,
  );

  generator.imageRaster(line);
}

Printing Tabular Rows

Receipts often need aligned columns for item name, quantity, and price. Use renderRow with fixed column widths:

final row = await UnicodeLinePrinter.renderRow(
  columns: ['চাল (৫ কেজি)', '২', '৳ ৪০০'],
  columnWidths: [0.5, 0.2, 0.3],
  fontSize: 24,
);

generator.imageRaster(row);

Real-World Use Case

Here is a practical example printing a full itemized receipt:

Future<List<int>> buildReceipt(List<Map<String, String>> items) async {
  final profile = await CapabilityProfile.load();
  final generator = Generator(PaperSize.mm80, profile);
  List<int> bytes = [];

  bytes += generator.text('দোকানের নাম', styles: PosStyles(align: PosAlign.center));

  for (final item in items) {
    final row = await UnicodeLinePrinter.renderRow(
      columns: [item['name']!, item['qty']!, item['price']!],
      columnWidths: [0.5, 0.2, 0.3],
      fontSize: 22,
    );
    bytes += generator.imageRaster(row);
  }

  bytes += generator.cut();
  return bytes;
}

Previewing Without Hardware

During development, render lines to PNG bytes to preview them on screen instead of sending them to a printer:

final previewBytes = await UnicodeLinePrinter.renderLinePreview(
  text: 'রসিদ প্রিভিউ',
  fontSize: 28,
);

Image.memory(previewBytes);

Platform Support

The package works across all Flutter platforms: Android, iOS, Linux, macOS, Web, and Windows.

Summary

The thermal_unicode_print package makes it possible to print Bangla, Arabic, Devanagari, and other Unicode scripts on standard ESC/POS thermal printers without memory blowing up as receipts get longer. If you are building POS software for markets where the built-in printer character sets fall short, this package is a drop-in solution alongside esc_pos_utils_plus.

Check it out on pub.dev or explore the source on GitHub.