YueWen/node_modules/pngjs/lib/packer-async.js

'use strict';

var util = require('util');
var Stream = require('stream');
var constants = require('./constants');
var Packer = require('./packer');

var PackerAsync = module.exports = function(opt) {
  Stream.call(this);

  var options = opt || {};

  this._packer = new Packer(options);
  this._deflate = this._packer.createDeflate();

  this.readable = true;
};
util.inherits(PackerAsync, Stream);


PackerAsync.prototype.pack = function(data, width, height, gamma) {
  // Signature
  this.emit('data', new Buffer(constants.PNG_SIGNATURE));
  this.emit('data', this._packer.packIHDR(width, height));

  if (gamma) {
    this.emit('data', this._packer.packGAMA(gamma));
  }

  var filteredData = this._packer.filterData(data, width, height);

  // compress it
  this._deflate.on('error', this.emit.bind(this, 'error'));

  this._deflate.on('data', function(compressedData) {
    this.emit('data', this._packer.packIDAT(compressedData));
  }.bind(this));

  this._deflate.on('end', function() {
    this.emit('data', this._packer.packIEND());
    this.emit('end');
  }.bind(this));

  this._deflate.end(filteredData);
};