Chrome app to enable raw printing from a browser
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README.md

Raw printing for Chrome

Chrome Apps are being discontinued by Google in 2018, so this project will no longer be actively developed. At the time of writing, neither WebUSB nor raw sockets can be used from regular web pages, so you will need to transition to a native app for this functionality once the runtime becomes unavailable.

Thank you to everybody who has used or contributed to this app over the past year and a half!


This is a Chrome app to allow browser-based Javascript code to pass raw data to a supported printer. It is aimed at developers of web-based point-of-sale systems where server-side printing is not feasable.

This has been developed for use with a USB receipt printer, with an ESC/POS command generator (escpos-php) providing the binary data.

The problem

It can be difficult to add printing to a web-based point-of-sale system:

  • The local print system does not use raw output, so you get low-quality, rasterised output.
  • Allowing inbound connectivity to allow a server to print requires a static IP, and is challenging to secure and debug.

This app solves the problem by exposing a websocket on localhost. A web-page can then retrieve binary print data from the server, and pass it to the app for printing.

Compatibility

Printer types

Only USB receipt printers are currently supported.

  • Networked printers may be supported in future.
  • Serial/Parallel printers may be accessed via a USB adaptor.
  • CUPS/IPP/Windows shared printers are out of scope at this stage, please hook in directly via USB.

Supported printers

Raw printing for Chrome is loaded with vendor/product ID's for the following printers:

  • Epson TM-T20
  • PL2305 Parallel Port
  • Winbond Virtual Com Port.

If your USB printer is not listed, please create a new issue to request support. Because of the way Chrome app permissions work, please include the USB vendor ID and product ID.

Page Description Languages

This app is simply a connector. In theory, any page description language is supported, provided that you are able to generate it, and your printer can understand it.

Installation

This application is not yet available in the Chrome store, so the installation steps are a bit unusual:

  • Download and extract the most recent release.
  • Under chrome://extensions, tick developer mode, and 'load unpacked extension', and locate the extracted folder.

screenshot

  • Launch the extension, select your printer
  • If not listed, find the USB product, vendor ID, add it to manifest.md, and restart.
  • Click print
  • If it doesn't print, check the error log and see the notes displayed on the app window for the basic things to check.
  • In particular, unload the usblp kernel module if applicable, as it will claim the USB interface to the printer.

Demo

A small example web-page available under example/, which will print a "Hello World" receipt in ESC/POS if the raw printing app is running, with an ESC/POS printer configured. Steps to try it out:

  • Run the app
  • Add a printer
  • Open the example web page
  • Click a few buttons and hope for output.

This was tested on an Epson TM-T20.

Build

yarn
gulp

The chrome-raw-print subfolder contains the compiled files.

Contribute

Pull requests are welcome and appreciated. This project is quite new, please see the issue tracker for ideas of things to work on.

Screenshot

screenshot