inkjet-emu

A JS library for printing from legacy PC emulators.

Features include

• Generic parallel port interface with no emulator dependency
• Supports the HP PCL 5e protocol, including color
• Page eject events with PNG thumbnails
• Prints multi-page PDFs
• Reliable rendering using GhostPDL compiled to WASM

Usage

import { InkjetEmulator } from "inkjet-emu";

const printer = new InkjetEmulator({
  // options
  thumbnail_ppi: 72,

  // printer -> emulator
  on_receive_status(value) {
    emulator.bus.send("parallel0-status-input", value);
  },

  // printer page previews
  on_page_eject(thumbnail) {
    console.log("PNG thumbnail bytes", thumbnail.byteLength);
  }
});

// emulator -> printer
emulator.add_listener("parallel0-data-output", value => {
  printer.send_data(value);
});
emulator.add_listener("parallel0-control-output", value => {
  printer.send_control(value);
});

// ...to collect a PDF when it's ready
const pdfBytes = printer.collect_pdf();

Building

Requires:

• Node 22+
• Emscripten, in particular emcmake must be in PATH

Building:

1. Initialize the git submodule. This is a one-time step and can be skipped in future builds

   git submodule update --init --recursive

2. To build (use "rebuild" to clean build artifacts first)

   npm run build

Testing

npm run test

API

InkjetEmulatorOptions

InkjetEmulator configuration options passed to constructor

| Field | Type | Description | | ----------------- | ------------------------------- | ------------------------------------------------------------------- | | thumbnail_ppi | number | Pixels per inch to render thumbnails | | on_receive_status | (value: byte) => void | Handler for when the printer drives the parallel port status lines. | | on_page_eject | (thumbnail: Uint8Array) => void | Handler for when the printer ejects a page. |

class InjetEmulator

| Method | Signature | Description | | -------------- | ---------------------------------------- | --------------------------------------------------- | | constructor() | (options: InkjetEmulatorOptions) => void | Latch data on the parallel port data lines | | send_data() | (value: byte) => void | Latch data on the parallel port data lines | | send_control() | (value: byte) => void | Drive the parallel port control lines. | | collect_pdf() | () => Promise<Uint8Array> | Flush print queue and generate PDF of its contents. |