// 图片延迟加载
~function(){
	
	function lazyImg(oImg) {
		// 进行加载过，直接返回
		if(oImg.isLoad)
			return;
		
		// 获取图片所在盒子距离body的上偏移和浏览器底边框距离body 的距离
		var a = utils.win('clientHeight') + utils.win('scrollTop');
		var oImgP = oImg.parentNode.parentNode; 
		var b = utils.offset(oImgP).top;
		if(a >= b) {
			oImg.isLoad = true; 
			var oTempImg = new Image;
			var dataSrc = oImg.getAttribute("data-src");
			
            oTempImg.onload = function () {
                oImg.src = this.src;
                oImg.style['display'] = 'block';
                //moveImg(oImg);
                oTempImg = null;
            };
            
            dataSrc = dataSrc === '' ? '/img/img_default.png' : dataSrc;
            oTempImg.src = dataSrc;
		}
		
	}
	
    //图片的透明度渐现
    function moveImg(oImg) {
        var start = 0,
            step = 0.08;
        oImg.moveTimer = setInterval(function () {
            if(start >= 1) {
                clearTimeout(oImg.moveTimer);
                return;
            }
            start += step;
            
            oImg['style']['opacity'] = start;
            oImg['style']['filter'] = 'alpha(opacity=' + start * 100 + ')';
            
        },17);
    }
	
	
	// 页面图片延迟加载
	function handleAllImg() {
		var imgList = document.getElementsByTagName('img');
		for(var i =0; i<imgList.length;i++) {
			var curImg = imgList[i];
			var dataSrc = curImg.getAttribute("data-src");
			if(dataSrc != null) {
				lazyImg(curImg);
			}
		}
	}
	
	// --> 设置页面加载和滚动条滚动时加载图片
	window.onload = window.onscroll = handleAllImg;
	
}();

var utils = (function() {
	// 返回元素距离body的偏移量
	function offset(curEle) {
		var l = curEle.offsetLeft,
			t = curEle.offsetTop,
			p = curEle.offsetParent;
		
		while(p && p !== document.body) {
			
			// IE8浏览器中offsetLeft已经包含了边框值
			if (window.navigator.userAgent.indexOf('MSIE 8') === -1) {
				l += p.clientLeft;
				t += p.clientTop;
			}
			
			l += p.offsetLeft;
			t += p.offsetTop;
			
			p = p.offsetParent;
		}
		
		return {left : l , top : t};
	}

	// 获取 浏览器属性
	function win(attr) {
		return document.documentElement[attr] || document.body[attr];
	}

	return {
		offset:offset,
		win:win
	};
	
})();