pngjs/lib/packer-async.js

'use strict';

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

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

  options.deflateChunkSize = options.deflateChunkSize || 32 * 1024;
  options.deflateLevel = options.deflateLevel != null ? options.deflateLevel : 9;
  options.deflateStrategy = options.deflateStrategy != null ? options.deflateStrategy : 3;
  options.inputHasAlpha = options.inputHasAlpha != null ? options.inputHasAlpha : true;
  options.deflateFactory = options.deflateFactory || zlib.createDeflate;
  options.bitDepth = options.bitDepth || 8;
  options.colorType = (typeof options.colorType === 'number') ? options.colorType : constants.COLORTYPE_COLOR_ALPHA;

  if (options.colorType !== constants.COLORTYPE_COLOR && options.colorType !== constants.COLORTYPE_COLOR_ALPHA) {
    throw new Error('option color type:' + options.colorType + ' is not supported at present');
  }
  if (options.bitDepth !== 8) {
    throw new Error('option bit depth:' + options.bitDepth + ' is not supported at present');
  }

  this._packer = new Packer(options);
  this._deflate = options.deflateFactory({
    chunkSize: options.deflateChunkSize,
    level: options.deflateLevel,
    strategy: options.deflateStrategy
  });

  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);
};