Package Exports

png-stream
png-stream/decoder
png-stream/encoder

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (png-stream) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

png-stream

A streaming PNG encoder and decoder for Node and the browser. Supports animated PNGs and normal still PNGs.

Installation

npm png-stream

For the browser, you can build using Browserify.

Decoding

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

var PNGDecoder = require('png-stream/decoder');
var concat = require('concat-frames');

// decode a PNG file to RGB pixels
fs.createReadStream('in.png')
  .pipe(new PNGDecoder)
  .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

You can encode a PNG by writing or piping pixel data to a PNGEncoder stream. The PNG encoder supports writing data in the RGB, RGBA, grayscale (gray), and grayscale + alpha (gray) color spaces. You can also write data in the indexed color space by first quantizing it using the neuquant module.

var PNGEncoder = require('png-stream/encoder');
var neuquant = require('neuquant');

// convert a JPEG to a PNG
fs.createReadStream('in.jpg')
  .pipe(new JPEGDecoder)
  .pipe(new PNGEncoder)
  .pipe(fs.createWriteStream('out.png'));
  
// write indexed data
fs.createReadStream('in.jpg')
  .pipe(new JPEGDecoder)
  .pipe(new neuquant.Stream)
  .pipe(new PNGEncoder)
  .pipe(fs.createWriteStream('indexed.png'));

License

MIT