. 代码如下:

<img src="http://tanglangrong2010.blog.163.com/blog/images/placeholder.png" lazy-src="http://tanglangrong2010.blog.163.com/blog/images/realimg.jpg" alt="" /> 
<!-- 如果浏览器禁用了js，我们也不能不让网页显示图片撒，所以最好是加上下面一句备用代码 --> 
<noscript><img src="http://tanglangrong2010.blog.163.com/blog/images/realimg.jpg" alt="" /></noscript> 

. 代码如下:

图片延迟加载插件代码 
(function( $ ){ 
$.fn.imglazyload = function( options ){ 
var o = $.extend({ 
attr : 'lazy-src', 
container : window, 
event : 'scroll', 
fadeIn : false, 
threshold : 0, 
vertical : true 
}, options ), 
event = o.event, 
vertical = o.vertical, 
container = $( o.container ), 
threshold = o.threshold, 
// 将jQuery对象转换成DOM数组便于操作 
elems = $.makeArray( $(this) ), 
dataName = 'imglazyload_offset', 
OFFSET = vertical ? 'top' : 'left', 
SCROLL = vertical ? 'scrollTop' : 'scrollLeft', 
winSize = vertical ? container.height() : container.width(), 
scrollCoord = container[ SCROLL ](), 
docSize = winSize + scrollCoord; 
// 延迟加载的触发器 
var trigger = { 
init : function( coord ){ 
return coord >= scrollCoord && 
coord <= ( docSize + threshold ); 
}, 
scroll : function( coord ){ 
var scrollCoord = container[ SCROLL ](); 
return coord >= scrollCoord && 
coord <= ( winSize + scrollCoord + threshold ); 
}, 
resize : function( coord ){ 
var scrollCoord = container[ SCROLL ](), 
winSize = vertical ? 
container.height() : 
container.width(); 
return coord >= scrollCoord && 
coord <= ( winSize + scrollCoord + threshold ); 
} 
}; 
var loader = function( triggerElem, event ){ 
var i = 0, 
isCustom = false, 
isTrigger, coord, elem, $elem, lazySrc; 
// 自定义事件只要触发即可，无需再判断 
if( event ){ 
if( event !== 'scroll' && event !== 'resize' ){ 
isCustom = true; 
} 
} 
else{ 
event = 'init'; 
} 
for( ; i < elems.length; i++ ){ 
isTrigger = false; 
elem = elems[i]; 
$elem = $( elem ); 
lazySrc = $elem.attr( o.attr ); 
if( !lazySrc || elem.src === lazySrc ){ 
continue; 
} 
// 先从缓存获取offset值，缓存中没有才获取计算值, 
// 将计算值缓存，避免重复获取引起的reflow 
coord = $elem.data( dataName ); 
if( coord === undefined ){ 
coord = $elem.offset()[ OFFSET ]; 
$elem.data( dataName, coord ); 
} 
isTrigger = isCustom || trigger[ event ]( coord ); 
if( isTrigger ){ 
// 加载图片 
elem.src = lazySrc; 
if( o.fadeIn ){ 
$elem.hide().fadeIn(); 
} 
// 移除缓存 
$elem.removeData( dataName ); 
// 从DOM数组中移除该DOM 
elems.splice( i--, 1 ); 
} 
} 
// 所有的图片加载完后卸载触发事件 
if( !elems.length ){ 
if( triggerElem ){ 
triggerElem.unbind( event, fire ); 
} 
else{ 
container.unbind( o.event, fire ); 
} 
$( window ).unbind( 'resize', fire ); 
elems = null; 
} 
}; 
var fire = function( e ){ 
loader( $(this), e.type ); 
}; 
// 绑定事件 
container = event === 'scroll' ? container : $( this ); 
container.bind( event, fire ); 
$( window ).bind( 'resize', fire ); 
// 初始化 
loader(); 
return this; 
}; 
})( jQuery );