How to reduce the file size of a PDF using Node.js

At Woovi, we allow our customers to upload their documents with arbitrary sizes without requiring them to reduce the file size on their side.

Therefore, when opening accounts, we need to perform this reduction on these documents. For this purpose, we have created an automated solution using Ghostscript with Node.js to handle the compression.

import { existsSync } from 'fs';
import fs from 'fs/promises';
import path from 'path';
import { promisify } from 'util';

const execPromise = promisify(exec);

const cwd = process.cwd();

const compressPdf = async (base64: string): Promise<string> => {
  try {
    const tempFolder = path.join(cwd, "temp");
    const hasTempFolder = existsSync(tempFolder);

    if (!hasTempFolder) {
      await fs.mkdir(tempFolder);
    }

    const originalFilePath = path.join(cwd, "temp", "original.pdf");
    const compressFilePath = path.join(cwd, "temp", "compress.pdf");

    await fs.writeFile(originalFilePath, base64, "base64");

    await execPromise(
      `gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile="${compressFilePath}" ${originalFilePath}`
    );

    const compressFileBase64 = await fs.readFile(compressFilePath, "base64");

    await fs.unlink(originalFilePath);
    await fs.unlink(compressFilePath);

    return compressFileBase64;
  } catch (error) {
    throw error;
  }
};

The above function creates a temporary folder to store the processed files and performs compression using Ghostscript parameters. The original file is saved in this temporary folder, and Ghostscript is used to generate a compressed version of the file. Then, the compressed file is read and converted into a base64 string.

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Photo by Dan Dennis on Unsplash