dottobr83 / apng-canvas

APNG implementation on canvas.

apng-canvas v2.1.0

(README по-русски)

Library to display Animated PNG (Wikipedia, specification) in a browser using canvas.

Working demo: https://davidmz.github.io/apng-canvas/ (around 3 Mb of apng files)

Please note! API version 2 of the library is incompatible with the API version 1!

The library requires support from the following technologies in order to run:

• Canvas
• Typed Arrays
• Blob URLs
• requestAnimationFrame

These technologies are supported in all modern browsers and IE starting with version 10.

Some browsers (at the moment these are Firefox and Safari 8+) have native support for APNG. This library is not required for these browsers.

Usage example

APNG.ifNeeded().then(function() {
    var images = document.querySelectorAll(".apng-image");
    for (var i = 0; i < images.length; i++) APNG.animateImage(images[i]);
});

Limitations

Images are loaded using XMLHttpRequest, therefore, the HTML page and APNG image must be located on the same domain or the correct CORS header should be provided (for example, Access-Control-Allow-Origin: *). For the same reason, the library will not work on a local machine (using the protocol file://).

Important note! Compression proxies (turbo mode in Opera, "reduce data usage" mode in mobile Chrome, etc.), doesn't know about APNG format. These proxies transforms APNGs into static images. To prevent it for your images, they need to be served with Cache-Control: no-transform HTTP header (see big article about such proxies), or via HTTPS.

API

The library creates a global object APNG, which has several methods.

High-level methods:

• APNG.ifNeeded
• APNG.animateImage
• APNG.releaseCanvas

Low-level methods:

• APNG.checkNativeFeatures
• APNG.parseBuffer
• APNG.parseURL
• APNG.animateContext

Most methods work asynchronously and return the ES6 Promise object. Most browsers have built-in support for it. For others browsers, library uses polifill (included in the library). If you have not worked before with Promises, then you should read the review paper about this technology. The method description includes values of the Promise result in cases where it is fulfilled or rejected.

Build instructions

npm install
gulp build