expo-esc-pos-utils

A powerful Expo module for ESC/POS printer utilities, supporting image printing and text formatting. This module provides easy-to-use utilities for working with thermal printers in React Native and Expo applications.

Features

• Image printing support
• Text formatting
• Network printer support
• Base64 image conversion
• ESC/POS command utilities

Installation

npm install expo-esc-pos-utils
# or
yarn add expo-esc-pos-utils

Usage

import ExpoEscPosUtils from 'expo-esc-pos-utils';
import { NetPrinter } from './net-printer';

// Example: Print an image
const printImage = async () => {
  const printer = new NetPrinter();
  try {
    // Connect to printer
    await printer.connect('192.168.1.100', 9100);
    await printer.initialize();

    // Convert and print image
    const base64Image = '...'; // Your base64 image string
    const intArray = await ExpoEscPosUtils.convertBase64ToGsV0Data(base64Image, 576);
    const uint8Array = new Uint8Array(intArray);
    await printer.printBitmap(uint8Array);
    printer.cut();
  } catch (error) {
    console.error('Printing error:', error);
  } finally {
    printer.disconnect();
  }
};

API Reference

convertBase64ToGsV0Data(base64: string, width: number): Promise<number[]>

Converts a base64 image to ESC/POS GS v0 command data.

• base64: Base64 encoded image string
• width: Width of the image in pixels
• Returns: Promise resolving to an array of numbers representing the ESC/POS command data

Contributing

Contributions are very welcome! Please refer to guidelines described in the contributing guide.

License

MIT

API documentation

• Documentation for the latest stable release
• Documentation for the main branch

Installation in managed Expo projects

For managed Expo projects, please follow the installation instructions in the API documentation for the latest stable release. If you follow the link and there is no documentation available then this library is not yet usable within managed projects — it is likely to be included in an upcoming Expo SDK release.

Installation in bare React Native projects

For bare React Native projects, you must ensure that you have installed and configured the expo package before continuing.

Add the package to your npm dependencies

npm install expo-esc-pos-utils

Configure for Android

Configure for iOS

Run npx pod-install after installing the npm package.