text: 'use strict';
  
  var util = require('util');
  var Stream = require('stream');
  var Parser = require('./parser-async');
  var Packer = require('./packer');
  var PNGSync = require('./png-sync');
  
  
  var PNG = exports.PNG = function(options) {
    Stream.call(this);
  
    options = options || {}; // eslint-disable-line no-param-reassign
  
    this.width = options.width || 0;
    this.height = options.height || 0;
  
    this.data = this.width > 0 && this.height > 0 ?
      new Buffer(4 * this.width * this.height) : null;
  
    if (options.fill && this.data) {
      this.data.fill(0);
    }
  
    this.gamma = 0;
    this.readable = this.writable = true;
  
    this._parser = new Parser(options);
  
    this._parser.on('error', this.emit.bind(this, 'error'));
    this._parser.on('close', this._handleClose.bind(this));
    this._parser.on('metadata', this._metadata.bind(this));
    this._parser.on('gamma', this._gamma.bind(this));
    this._parser.on('parsed', function(data) {
      this.data = data;
      this.emit('parsed', data);
    }.bind(this));
  
    this._packer = new Packer(options);
    this._packer.on('data', this.emit.bind(this, 'data'));
    this._packer.on('end', this.emit.bind(this, 'end'));
    this._parser.on('close', this._handleClose.bind(this));
    this._packer.on('error', this.emit.bind(this, 'error'));
  
  };
  util.inherits(PNG, Stream);
  
  PNG.sync = PNGSync;
  
  PNG.prototype.pack = function() {
  
    if (!this.data || !this.data.length) {
      this.emit('error', 'No data provided');
      return this;
    }
  
    process.nextTick(function() {
      this._packer.pack(this.data, this.width, this.height, this.gamma);
    }.bind(this));
  
    return this;
  };
  
  
  PNG.prototype.parse = function(data, callback) {
  
    if (callback) {
      var onParsed, onError;
  
      onParsed = function(parsedData) {
        this.removeListener('error', onError);
  
        this.data = parsedData;
        callback(null, this);
      }.bind(this);
  
      onError = function(err) {
        this.removeListener('parsed', onParsed);
  
        callback(err, null);
      }.bind(this);
  
      this.once('parsed', onParsed);
      this.once('error', onError);
    }
  
    this.end(data);
    return this;
  };
  
  PNG.prototype.write = function(data) {
    this._parser.write(data);
    return true;
  };
  
  PNG.prototype.end = function(data) {
    this._parser.end(data);
  };
  
  PNG.prototype._metadata = function(metadata) {
    this.width = metadata.width;
    this.height = metadata.height;
  
    this.emit('metadata', metadata);
  };
  
  PNG.prototype._gamma = function(gamma) {
    this.gamma = gamma;
  };
  
  PNG.prototype._handleClose = function() {
    if (!this._parser.writable && !this._packer.readable) {
      this.emit('close');
    }
  };
  
  
  PNG.bitblt = function(src, dst, srcX, srcY, width, height, deltaX, deltaY) { // eslint-disable-line max-params
  
    if (srcX > src.width || srcY > src.height || srcX + width > src.width || srcY + height > src.height) {
      throw new Error('bitblt reading outside image');
    }
  
    if (deltaX > dst.width || deltaY > dst.height || deltaX + width > dst.width || deltaY + height > dst.height) {
      throw new Error('bitblt writing outside image');
    }
  
    for (var y = 0; y < height; y++) {
      src.data.copy(dst.data,
        ((deltaY + y) * dst.width + deltaX) << 2,
        ((srcY + y) * src.width + srcX) << 2,
        ((srcY + y) * src.width + srcX + width) << 2
      );
    }
  };
  
  
  PNG.prototype.bitblt = function(dst, srcX, srcY, width, height, deltaX, deltaY) { // eslint-disable-line max-params
  
    PNG.bitblt(this, dst, srcX, srcY, width, height, deltaX, deltaY);
    return this;
  };
  
  PNG.adjustGamma = function(src) {
    if (src.gamma) {
      for (var y = 0; y < src.height; y++) {
        for (var x = 0; x < src.width; x++) {
          var idx = (src.width * y + x) << 2;
  
          for (var i = 0; i < 3; i++) {
            var sample = src.data[idx + i] / 255;
            sample = Math.pow(sample, 1 / 2.2 / src.gamma);
            src.data[idx + i] = Math.round(sample * 255);
          }
        }
      }
      src.gamma = 0;
    }
  };
  
  PNG.prototype.adjustGamma = function() {
    PNG.adjustGamma(this);
  };
  