README.md

Node APNG

A Node library for stitching Buffers containing PNG image data together to form an APNG image.

This library is based on code by Józef Sokołowski. I've fixed two bugs in it:

• IDAT chunk CRC calculation was being passed slice range, not the slice buffer
• PNGs with multiple IDAT chunks only had their first IDAT chunk considered

Usage

npm install https://github.com/TomasHubelbauer/node-apng

const apng = require('node-apng');
const fs = require('fs-extra');

void async function () {
  const buffers = [/* … */]; // Buffers of PNG image data
  // The callback is for frame duration: `numeration/denominator` seconds
  const buffer = apng(buffers, index => ({ numerator: 1, denominator: 10 }));
  await fs.writeFile('apng.png', buffer);
}()

To-Do

Add a GitHub Action for tests

Refactor as per the code comment

Add support for "skip first frame" to allow "warning this is animated" frame

The first frame should be skipped in the animation and should be a preview with a subtitle which says this is an animated image and your browser doesn't support APNG so you're getting only a preview.

APNG on GitHub

GitHub repository file preview page will only preview images with a PNG extension, but will animate properly (depending on browser support) if animated.

GitHub MarkDown renderer allows image sources with both PNG and APNG extensions. Will animate properly subject to browser support.

APNG in VS Code

VS Code will correctly preview and animate images as long as they have a PNG extension, not APNG extension.