PDFium.js

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

$3

``bash
yarn add pdfium.js
`

`bash
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.

`ts
import { PDFium } from "pdfium.js";

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

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

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

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Here is simple code snippets about memory management.

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

`ts
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);
});
``

PDFium API

This library doesn't provide full PDFium API yet. Check full version of defined PDFium API type list here.

You can also find original API specification here.

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- _FPDF_InitLibrary
- _FPDF_InitLibraryWithConfig
- _FPDF_DestroyLibrary
- _FPDF_GetLastError
- _FPDF_LoadDocument
- _FPDF_LoadMemDocument
- _FPDF_CloseDocument
- _FPDF_GetPageCount
- _FPDF_LoadPage
- _FPDF_GetPageWidth
- _FPDF_GetPageHeight
- _FPDF_GetPageWidthF
- _FPDF_GetPageHeightF
- _FPDF_GetPageSizeByIndex
- _FPDF_ClosePage
- _FPDFPage_CountObjects
- _FPDFPage_GetObject
- _FPDFPage_GenerateContent
- _FPDFPageObj_Destroy
- _FPDFText_LoadPage
- _FPDFText_CountChars
- _FPDFText_GetCharBox
- _FPDFText_ClosePage
- _FPDFBitmap_Create
- _FPDFBitmap_CreateEx
- _FPDFBitmap_FillRect
- _FPDF_RenderPageBitmap
- _FPDFBitmap_Destroy
- _FPDF_DeviceToPage
- _FPDF_PageToDevice

Author

- Jaewook Ahn

License

This project is licensed under the MIT License.