Extract first page of the PDF as cover image

extractPDFCoverImage.ts

import fs from "fs";
import { PDFDocument } from "pdf-lib";
import { fromBuffer } from "pdf2pic";
import path from "path";

const OUTPUT_IMAGE_DPI = 200;

export async function extractPDFCoverImage(
  pdfFilePath: string,
  coverOutputPath: string
) {
  try {
    // Read the existing PDF into a buffer
    const existingPdfBytes: Buffer = fs.readFileSync(pdfFilePath);

    // Load the PDF with pdf-lib
    const pdfDoc = await PDFDocument.load(existingPdfBytes);
    const pdfDimensions = await getCoverPageDimensions(pdfDoc);

    // we need a new pdf doc to get buffer which will be used by pdf2pic
    const newPdfDoc = await PDFDocument.create();

    // Copy the cover page from the existing PDF into the new PDF
    const [coverPage] = await newPdfDoc.copyPages(pdfDoc, [0]);
    newPdfDoc.addPage(coverPage);

    // Serialize the PDF to bytes and write it to the file system
    const newPdfBytes: Uint8Array = await newPdfDoc.save();

    const newPdfBuffer = Buffer.from(newPdfBytes);

    // now we can start converting the pdf to image
    const coverOutputPathParts = parseFilePath(coverOutputPath);
    const options = {
      density: OUTPUT_IMAGE_DPI,
      ...coverOutputPathParts,
      ...pdfDimensions,
    };
    const convert = fromBuffer(newPdfBuffer, options);
    const pageToConvertAsImage = 1;

    await convert(pageToConvertAsImage, { responseType: "image" });
  } catch (err) {
    console.error("Error:", err);
  }
}

function parseFilePath(absolutePath: string) {
  const ext = path.extname(absolutePath).substring(1); // Get extension without the dot
  const filename = path.basename(absolutePath, `.${ext}`); // Get filename without extension
  const directory = path.dirname(absolutePath); // Get directory path

  return {
    saveFilename: filename,
    savePath: directory,
    format: ext,
  };
}

async function getCoverPageDimensions(pdfDoc: PDFDocument): Promise<{
  width: number;
  height: number;
}> {
  const coverPagePdf = pdfDoc.getPages()[0];
  // Get the dimensions
  return coverPagePdf.getSize();
}

const pdfFilePath = "existing.pdf";
// Call the function
extractAndConvertCoverPage(pdfFilePath, "/tmp/pdf-cover/cover_page12333.png");