gif-stream

A streaming GIF encoder and decoder for Node and the browser

Installation

npm install gif-stream

For the browser, you can build using Browserify.

Decoding Example

This example uses the concat-frames module to collect the output of the GIF decoder into an array of frame objects.

var GIFDecoder = require('gif-stream/decoder');
var concat = require('concat-frames');

// decode a GIF file to RGB pixels
fs.createReadStream('in.gif')
  .pipe(new GIFDecoder)
  .pipe(concat(function(frames) {
    // frames is an array of frame objects
    // each one has a `pixels` property containing
    // the raw RGB pixel data for that frame, as
    // well as the width, height, etc.
  }));

Encoding Example

You can encode a GIF by writing or piping indexed/quantized data to a GIFEncoder stream. If you write data to it manually, you need to first quantize the pixel data to produce a color palette and a buffer of indexed pixels. You can use the neuquant module to do this.

Alternatively, if you have a stream of RGB data already, you can pipe it first to a neuquant stream, and then to a GIF encoder, which will do the hard work of quantizing and writing indexed data for you.

var GIFEncoder = require('gif-stream/encoder');
var neuquant = require('neuquant');

// encode an animated GIF file by writing pixels to it.
// you need to manually quantize the data to produce a palette and indexed pixels.
var q = neuquant.quantize(pixels);

var enc = new GIFEncoder(width, height, { palette: q.palette });
enc.pipe(fs.createWriteStream('out.gif'));

// write indexed data
enc.end(q.indexed);

// or, pipe data from another RGB stream
// boom: streaming image transcoding!
fs.createReadStream('rgb.png')
  .pipe(new PNGDecoder)
  .pipe(new neuquant.Stream)
  .pipe(new GIFEncoder)
  .pipe(fs.createWriteStream('out.gif'));

// maybe you want to preserve the original palette and indexing?
// you can do that too!
fs.createReadStream('rgb.png')
  .pipe(new GIFDecoder({indexed: true}))
  .pipe(new GIFEncoder)
  .pipe(fs.createWriteStream('out.gif'));
// somewhat useless example, but this may be useful for instance
// if you are breaking an animated GIF into multiple static GIFs

License

MIT