pdf-darker

Convert PDF files to dark mode with pixel-perfect rendering and preserved text layer.

Built with MuPDF.js (the same C engine as PyMuPDF) — no wrong text, no wrong fonts.

npm install -g pdf-darker

Or use directly with pnpm:

git clone <repo>
cd pdf-darker
pnpm install
pnpm build

# Basic conversion (output: input-dark.pdf)
pnpm convert input.pdf

# Specify output path
pnpm convert input.pdf output-dark.pdf

# With options
pnpm convert input.pdf --dpi 200 --no-text

# Or globally installed
pdf-darker input.pdf output-dark.pdf

# Start the web server on http://localhost:3000
pnpm server

import { Converter } from '@pdf-darker/core';

const converter = new Converter();
const result = await converter.convert(
  'input.pdf',
  'output-dark.pdf',
  {
    dpi: 300,
    quality: 95,
    preserveText: true,
    preserveForms: true,
    preserveLinks: true,
  },
  (progress) => {
    console.log(`Page ${progress.page}/${progress.totalPages} — ${progress.phase}`);
  },
);

console.log(`Done! ${result.pageCount} pages in ${result.durationMs}ms`);

1. Render each page to a high-resolution image via MuPDF
2. Apply luminance inversion — preserves hue while inverting brightness
3. Apply gamma correction — boosts midtones for readability
4. Create new PDF with inverted page images
5. Overlay hidden text layer — keeps text selectable and searchable

packages/
├── shared/     — Types and constants
├── core/       — PDF engine (MuPDF.js WASM)
├── tui/        — Terminal UI (Ink + React)
└── ui/         — Web UI (React + Vite + HTTP server)

See ARCHITECTURE.md and ALGORITHM.md for details.

AGPL-3.0 (same as MuPDF.js)