Pdfium.js NPM | npm.io

A PDFium wrapper library for browser-side JavaScript

Introduction

PDFium is a high performance open source PDF library used in chromium. However, its implementation in C/C++ makes it challenging to use in web development. PDFium.js provides a pre-built WebAssembly version of the PDFium binary and offers an interface that allows it to be used in JavaScript. It will be helpful when developing PDF-related features.

Getting Started

Installation

yarn add pdfium.js

npm install --save pdfium.js

Usage

!NOTE When you call PDFium(), this library will load and instantiate PDFium binary in browser environment. If your project is using SSR, such as Next.js, it should not be loaded in server-side environment. "use client"; directive might be required.

import { PDFium } from "pdfium.js";

PDFium().then((PDFiumModule) => {
  // library initialization
  PDFiumModule._FPDF_InitLibrary();

  // memory allocation
  const byteArray: Uint8Array = <FILE BINARY DATA>;
  const fileSize = byteArray.length;
  const binaryAddress = PDFiumModule.asm.malloc(fileSize);
  PDFiumModule.HEAPU8.set(byteArray, binaryAddress);

  // document loading
  const documentAddress = PDFiumModule._FPDF_LoadMemDocument(binaryAddress, fileSize, "");
});

WASM Memory Management

Here is simple code snippets about memory management.

The WASM Memory can be found in PDFiumModule.FPDF.HEAP* properties.

import { PDFium, memory } from "pdfium.js";

// options parameter can be skipped after the module loaded
PDFium().then((PDFiumModule) => {
  const nBytes = 1024;

  // allocate 1024 bytes in wasm memory
  const memoryAddress = PDFiumModule.wasmExports.malloc(nBytes);

  // you can also use calloc() to allocate 1024 bytes (array of 256 integers)
  const memoryAddress2 = memory.calloc(256, 4);

  // zero-fill allocated memory
  memory.fill(PDFiumModule.FPDF.HEAPU8, memoryAddress, nBytes);

  // free memory
  PDFiumModule.wasmExports.free(memoryAddress);
});