(function($) {
  $.fn.extend({
    resizeimg: function(opt, callback) {
      var defaults = {
        w: 200,
        h: 150
      },
          opts = $.extend(defaults, opt);

      //获取图片实际宽高，此方法摘自网络
      var getimgwh = function(url, callback) {
        var width, height, intervalid, check, div, img = new image(),
            body = document.body;
        img.src = url;

        //从缓存中读取
        if (img.complete) {
          return callback(img.width, img.height);
        };

        //通过占位提前获取图片头部数据
        if (body) {
          div = document.createelement('div');
          div.style.csstext = 'visibility:hidden;position:absolute;left:0;top:0;width:1px;height:1px;overflow:hidden';
          div.appendchild(img)
          body.appendchild(div);
          width = img.offsetwidth;
          height = img.offsetheight;
          check = function() {
            if (img.offsetwidth !== width || img.offsetheight !== height) {
              clearinterval(intervalid);
              callback(img.offsetwidth, img.clientheight);
              img.onload = null;
              div.innerhtml = '';
              div.parentnode.removechild(div);
            };
          };
          intervalid = setinterval(check, 150);
        };
        // 加载完毕后方式获取
        img.onload = function() {
          callback(img.width, img.height);
          img.onload = img.onerror = null;
          clearinterval(intervalid);
          body && img.parentnode.removechild(img);
        };
      };

      this.each(function() {
        var _this = this;
        getimgwh(this.src, function(imgwidth, imgheight) {
          //计算图片最大宽度						
          if (imgwidth > opts["w"]) {
            _this.width = opts["w"];
            _this.height = imgheight * (opts["w"] / imgwidth);
            imgwidth = opts["w"];
            imgheight = _this.height;
          }
          //计算图片最大高度
          if (imgheight > opts["h"]) {
            _this.height = opts["h"];
            _this.width = imgwidth * (opts["h"] / imgheight);
            imgheight = opts["h"];
            imgwidth = _this.width;
          }

          //水平居中，垂直居中
          // $(_this).css({
          //   "margin-top": (opts["h"] - imgheight) / 2,
          //   "margin-left": (opts["w"] - imgwidth) / 2
          // });

        });

      });
    }
  });
})(jquery);