node-pptx-png

High-fidelity PPTX to PNG converter for Node.js.

Overview

node-pptx-png is a pure JavaScript/TypeScript library for converting PowerPoint (PPTX) presentations to high-quality PNG images. It uses native canvas rendering (via skia-canvas) for accurate slide reproduction without relying on LibreOffice, Puppeteer, or other external dependencies.

Features

• Pure Node.js - No external dependencies like LibreOffice or headless browsers
• High fidelity - Skia-based rendering for accurate slide reproduction
• TypeScript - Full type definitions included
• Configurable - Control output size, format, and quality
• PNG optimization - Optional Sharp integration for 60-70% smaller files
• Theme support - Proper resolution of PowerPoint theme colors and fonts
• Rich content support:
  • Shapes with preset geometries (rectangles, chevrons, arrows, etc.)
  • Text with full styling (fonts, colors, bullets, alignment)
  • Images (embedded and linked)
  • Tables with cell formatting
  • Charts (bar, line, pie)
  • Backgrounds (solid, gradient, image)
  • Master/layout inheritance

Installation

npm install node-pptx-png

Prerequisites

This library uses skia-canvas for rendering. It should work out of the box on most systems, but you may need:

On macOS:

brew install pkg-config

On Ubuntu/Debian:

sudo apt-get install build-essential libfontconfig1-dev

Usage

Basic Usage

import { PptxImageRenderer } from 'node-pptx-png';
import * as fs from 'fs';

const renderer = new PptxImageRenderer();

// Render all slides
const result = await renderer.renderPresentation('./presentation.pptx', {
  format: 'png',
  scale: 1.0
});

for (const slide of result.slides) {
  if (slide.imageData) {
    fs.writeFileSync(`slide-${slide.slideNumber}.png`, slide.imageData);
  }
}

With Options

import { PptxImageRenderer } from 'node-pptx-png';

const renderer = new PptxImageRenderer({ logLevel: 'info' });

const result = await renderer.renderPresentation('./presentation.pptx', {
  scale: 0.5,              // Scale factor (0.5 = half size)
  format: 'png',           // Output format
  slideNumbers: [1, 2, 3], // Optional: render only specific slides
});

With PNG Optimization

For smaller file sizes, enable PNG optimization (requires sharp to be installed):

npm install sharp

import { PptxImageRenderer } from 'node-pptx-png';

const renderer = new PptxImageRenderer();

// Use the 'web' preset for maximum compression (60-70% smaller)
const result = await renderer.renderPresentation('./presentation.pptx', {
  pngOptimization: 'web'
});

// Or use other presets
const result2 = await renderer.renderPresentation('./presentation.pptx', {
  pngOptimization: 'balanced'  // ~2-3% smaller, lossless
});

// Or use custom options
const result3 = await renderer.renderPresentation('./presentation.pptx', {
  pngOptimization: {
    compressionLevel: 9,
    adaptiveFiltering: true,
    palette: true,
    colors: 128,
    quality: 80
  }
});

Rendering from Buffer

import { PptxImageRenderer } from 'node-pptx-png';
import * as fs from 'fs';

const pptxBuffer = fs.readFileSync('./presentation.pptx');
const renderer = new PptxImageRenderer();
const result = await renderer.renderPresentation(pptxBuffer);

API Reference

PptxImageRenderer

Main class for rendering presentations.

Constructor

new PptxImageRenderer(options?: { logLevel?: 'debug' | 'info' | 'warn' | 'error' | 'silent' })

Methods

renderPresentation(input, options?)

Renders all slides (or specified slides) in a presentation.

• input: Buffer | string - File path or buffer containing PPTX data
• options: RenderOptions - Optional rendering options
• Returns: Promise<PresentationRenderResult>

getSlideCount(input)

Gets the number of slides in a presentation.

• input: Buffer | string - File path or buffer containing PPTX data
• Returns: Promise<number>

RenderOptions

| Option | Type | Default | Description | |--------|------|---------|-------------| | scale | number | 1.0 | Scale factor for output size | | format | 'png' | 'png' | Output format | | slideNumbers | number[] | all | Specific slides to render (1-based) | | pngOptimization | string \| object | 'none' | PNG optimization preset or custom options |

PNG Optimization Presets

| Preset | Size Reduction | Description | |--------|----------------|-------------| | 'none' | 0% | No optimization (fastest) | | 'fast' | ~1-2% | Quick lossless compression | | 'balanced' | ~2-3% | Lossless with adaptive filtering | | 'maximum' | ~2-3% | Best lossless compression | | 'web' | 60-70% | Palette quantization (may affect photo quality) |

PngOptimizationOptions

For custom PNG optimization:

| Option | Type | Default | Description | |--------|------|---------|-------------| | compressionLevel | number | 6 | Compression level (0-9, higher = smaller) | | adaptiveFiltering | boolean | true | Use adaptive row filtering | | palette | boolean | false | Convert to indexed PNG (max 256 colors) | | colors | number | 256 | Max colors for palette mode (2-256) | | quality | number | 90 | Palette quantization quality (1-100) | | dither | number | 1.0 | Dithering strength for palette mode (0-1) |

SlideRenderResult

| Property | Type | Description | |----------|------|-------------| | slideIndex | number | Zero-based slide index | | slideNumber | number | One-based slide number | | imageData | Buffer | Rendered image data | | width | number | Image width in pixels | | height | number | Image height in pixels | | success | boolean | Whether rendering succeeded | | errorMessage | string? | Error message if failed |

PresentationRenderResult

| Property | Type | Description | |----------|------|-------------| | slides | SlideRenderResult[] | Results for each slide | | totalSlides | number | Total number of slides | | successfulSlides | number | Number of successfully rendered slides | | allSuccessful | boolean | Whether all slides rendered successfully |

Supported Features

Shapes

• Rectangles, rounded rectangles
• Chevrons, arrows, pentagons
• Ellipses, circles
• Lines and connectors
• Custom geometries

Text

• Font families and sizes
• Bold, italic, underline, strikethrough
• Text colors (solid and theme colors)
• Bullet points and numbered lists
• Paragraph alignment
• Line spacing
• Superscript/subscript

Fills

• Solid colors
• Theme/scheme colors (accent1-6, dk1, lt1, etc.)
• Gradients (linear)
• Picture fills

Tables

• Cell backgrounds
• Borders
• Merged cells
• Text formatting within cells

Charts

• Bar/column charts
• Line charts
• Pie charts
• Chart titles and legends

Other

• Background images
• Master slide inheritance
• Layout inheritance
• Placeholder resolution
• Shape effects (shadows)

Development

# Install dependencies
npm install

# Build
npm run build

# Run tests
npm test

# Type check
npx tsc --noEmit

# Render a test presentation
npx ts-node scripts/render-pptx.ts ./test.pptx ./output

License

MIT