fsk-imgoptimize/lib/imgOptimize.js

图片优化工具

var Writable = require('stream').Writable;
var Readable = require('stream').Readable;
var util = require('util');
util.inherits(ImgOptimize, Readable);
var _keys = Object.keys(Writable.prototype);
for(var v = 0, len = _keys.length; v < len; v++) {
  var method = _keys[v];
  if (!ImgOptimize.prototype[method]) {
    ImgOptimize.prototype[method] = Writable.prototype[method];
  }
}
function ImgOptimize(options) {
  if (!(this instanceof ImgOptimize)) {
    return new ImgOptimize(options);
  }
  Writable.call(this, options);
  Readable.call(this, options);
  this.writable = true;
  this.readable = true;
  options = options || {};
  if (options.writable === false) {
    this.writable = false;
  }
  if (options.readable === false) {
    this.readable = false;
  }
  this._encoding = options.encoding;
  this._buffers = [];
  this._constants = null;
  this._size = 0;
  this._queue = [];
  this.handleSignature();
}
ImgOptimize.prototype._read = function(length) {
};
ImgOptimize.prototype.write = function(data, encoding) {
  if (!this.writable) {
    throw new Error('cannot write');
  }
  if (!util.isBuffer(data)) {
    data = new Buffer(data, encoding || this._encoding);
  }
  this._buffers.push(data);
  this._size += data.length;
  this._process();
};

ImgOptimize.prototype._process = function() {
  while(this._queue.length && this._buffers.length && this._size > 0) {
    var chunk = this._queue[0];
    var len = chunk.length;
    if (chunk && len <= this._size) {
      this._queue.shift();
      var pos = 0;
      var index = 0;
      var buffer = new Buffer(len);
      while (pos < chunk.length) {
        var current = this._buffers[index++];
        var minLen = Math.min(len - pos, current.length);
        current.copy(buffer, pos, 0, minLen);
        pos += minLen;
        if (minLen !== current.length) {
          this._buffers[--index] = current.slice(minLen);
        }
      }
      if (index) {
        this._buffers.splice(0, index);
      }
      this._size -= len;
      chunk.callback.call(this, buffer);
    } else {
      break;
    }
  }
};

ImgOptimize.prototype.addHandle = function(length, callback) {
  this._queue.push({
    length: length,
    callback: callback
  });
  this._process();
};
ImgOptimize.prototype.end = function(data, encoding) {
  data && this.write(data, encoding);
  this.writable = false;
};

module.exports = ImgOptimize;