png-stream
A streaming PNG encoder and decoder for Node and the browser. Supports animated PNGs and normal still PNGs.
Installation
npm install 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
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