compare-pdf-ts

Node package that compares PDF files via pixel comparison. Largely inspired by the pdf-compare package, however this package differs in that it does everything in-memory without the need for reading/writing files.

Dependencies

This package requires the following dependencies in your project:

• pdf-dist
• @napi-rs/canvas

Setup

Install this package and required dependencies:

npm install compare-pdf-ts
npm install pdf-dist
npm install @napi-rs/canvas

Usage

import { comparePdfs } from "compare-pdf-ts";

const pdf1 = readFileSync("./example1.pdf");
const pdf2 = readFileSync("./example2.pdf");

const { equal, diffs } = await comparePdfs(pdf1, pdf2);

if (!equal) {
  diffs.forEach(({ diffPng, pageNumber }) => {
    writeFileSync(`page-${pageNumber}-diff.png`, diffPng);
  });
}

Comparison Options

You can optionally pass some options when calling the comparePdfs function to tailor its behavior:

const { equal, diffs } = await comparePdfs(pdf1, pdf2, {
  pngScale: 1.5
  diffThreshold: 0.2
});

The options type:

type ComparePdfsOptions = {
  pngScale: number;
  considerAntiAliasing: boolean;
  includeDiffMask: boolean;
  diffThreshold: number;
  diffAlpha: number;
  diffAntiAliasingColor: [number, number, number];
  diffColor: [number, number, number];
  diffColorAlt: [number, number, number];
};

The default option values:

const DEFAULT_COMPARE_PDFS_OPTIONS: ComparePdfsOptions = {
  pngScale: 1.0,
  considerAntiAliasing: false,
  includeDiffMask: false,
  diffThreshold: 0.1,
  diffAlpha: 0.1,
  diffAntiAliasingColor: [255, 255, 0],
  diffColor: [255, 0, 0],
  diffColorAlt: [255, 0, 0],
};