Render PDF to Image

Load PDF document

using document = await pdfium.openDocument(buff);

// ... do something with the document

// Automatically disposed when scope exits

Render PDF page

Get a page from the document by index (starting from 0):

using page = document.getPage(0);

Or iterate over all pages:

for (const page of document.pages()) {
  using p = page;
  // ... do something with the page
}

Then render the page by calling the render method. It accepts an optional RenderOptions object:

scale - scale factor for the image (default: 1, which means 72 DPI; 3 is almost always enough for good quality)
width / height - target dimensions in pixels (overrides scale, does not preserve aspect ratio)
renderFormFields - whether to render interactive form fields (default: false)
backgroundColour - ARGB background colour integer (default: 0xFFFFFFFF — white)
rotation - rotation to apply during rendering

const { data, width, height } = page.render({ scale: 3 });
// data is a Uint8Array of RGBA pixels (4 bytes per pixel)

To render with form fields visible:

const result = page.render({ scale: 3, renderFormFields: true });

Result

The render result contains:

data - RGBA pixel data as a Uint8Array
width - rendered width in pixels
height - rendered height in pixels
originalWidth - original page width in points (before scaling)
originalHeight - original page height in points (before scaling)

Converting to PNG with sharp

To convert the raw RGBA pixels to a PNG image, use the sharp library:

pnpm add sharp

import sharp from 'sharp';

const { data, width, height } = page.render({ scale: 3 });

const png = await sharp(data, {
  raw: { width, height, channels: 4 },
}).png().toBuffer();

Using width and height instead of scale

You can use width and height options instead of scale to specify exact pixel dimensions. The aspect ratio will not be preserved — the image will be stretched to the specified size.

const result = page.render({ width: 800, height: 600 });

Full example

import { PDFium } from '@scaryterry/pdfium';
import { promises as fs } from 'fs';
import sharp from 'sharp';

async function main() {
  const buff = await fs.readFile('document.pdf');

  // Initialise the library
  using pdfium = await PDFium.init();

  // Open the document
  using document = await pdfium.openDocument(buff);

  // Render each page to PNG
  for (const page of document.pages()) {
    using p = page;
    console.log(`Page ${p.index} - rendering...`);

    const { data, width, height } = p.render({ scale: 3 });

    const png = await sharp(data, {
      raw: { width, height, channels: 4 },
    }).png().toBuffer();

    await fs.writeFile(`output/${p.index}.png`, png);
  }
}

main();