总结HTML全屏背景的方法

全屏背景是当下比较流行的一种网页设计风格，而具体的实现这样的全屏背景无外乎基本就两种方法，一种的通过CSS去实现的(CSS3.0为我们提供了更为丰富的CSS样式控制)；另一种就是通过我们熟悉的javascript去实现，这里为了代码方便就直接使用jQuery了。既然提到jQuery，我们就可以想象既然我们能用jQuery写了，那网络上就一定有类似的写好的jQuery插件等着我们用了。

方法一、利用CSS3.0样式新特性实现北京全屏 (不支持ie6-8)

html {
      background: url(images/bg.jpg) no-repeat center center fixed;
      -webkit-background-size: cover;
      -moz-background-size: cover;
      -o-background-size: cover;
      background-size: cover;
}

或：

html{
    background:url('background.jpg') no-repeat center center;
    min-height:100%;
    background-size:cover;
}
body{
    min-height:100%;
}

原理：将html及body设置为最小高度为100%，使用css3中的background-size:cover;将背景图片设置成封面全屏模式。

兼容性：

Safari 3+

Chrome Whatever+

IE 9+

Opera 10+

Firefox 3.6+

方法二、使用jQuery实现

HTML代码：

<img src="images/bg.jpg" id="bg" alt="">

CSS代码：

#bg { position: fixed; top: 0; left: 0; }
.bgwidth { width: 100%; }
.bgheight { height: 100%; }

jQuery代码：

$(window).load(function() {  
    var theWindow        = $(window),
        $bg              = $("#bg"),
        aspectRatio      = $bg.width() / $bg.height();
                                                                                                                                                                            
    function resizeBg() {
                                                                                                                                                    
        if ( (theWindow.width() / theWindow.height()) < aspectRatio ) {
            $bg
                .removeClass()
                .addClass('bgheight');
        } else {
            $bg
                .removeClass()
                .addClass('bgwidth');
        }
                                                                                                                                                                
    }
                                                                                                                                                                            
    theWindow.resize(resizeBg).trigger("resize");
});

兼容性：

IE7+

任何桌面浏览器

方法二、使用jQuery实现(附)【使用jQuery插件jQuery.fullBg】

First comes the plugin code:

/**
 * jQuery.fullBg
 * Version 1.0
 * Copyright (c) 2010 c.bavota - http://bavotasan.com
 * Dual licensed under MIT and GPL.
 * Date: 02/23/2010
**/
(function($) {
  $.fn.fullBg = function(){
    var bgImg = $(this);      
                                                   
    function resizeImg() {
      var imgwidth = bgImg.width();
      var imgheight = bgImg.height();
                                                           
      var winwidth = $(window).width();
      var winheight = $(window).height();
                                                       
      var widthratio = winwidth / imgwidth;
      var heightratio = winheight / imgheight;
                                                           
      var widthdiff = heightratio * imgwidth;
      var heightdiff = widthratio * imgheight;
                                                       
      if(heightdiff>winheight) {
        bgImg.css({
          width: winwidth+'px',
          height: heightdiff+'px'
        });
      } else {
        bgImg.css({
          width: widthdiff+'px',
          height: winheight+'px'
        });   
      }
    }
    resizeImg();
    $(window).resize(function() {
      resizeImg();
    });
  };
})(jQuery)

There is only a little CSS needed for this one:

.fullBg {
  position: absolute;
  top: 0;
  left: 0;
  overflow: hidden;
}
#maincontent {
  position: absolute;
  top: 0;
  left: 0;
  z-index: 50;
}

If you want your background to stay fixed you can change the .fullBG CSS to this:

.fullBg {
  position: fixed;
  top: 0;
  left: 0;
  overflow: hidden;
}

For the HTML markup, you can just add an image tag with an id or class, but you also need to add a div that contains your main content or else it won’t work properly. This is the bare minimum:

<img src="your-background-image.jpg" alt="" id="background" />
<div id="maincontent">
  <!-- Your site content goes here -->
</div>

To call the jQuery function, add this to the bottom of your web page, right before the closing body tag:

<script type="text/javascript">
$(window).load(function() {
    $("#background").fullBg();
});
</script>

Once again, this plugin is pretty simple so no options are available. It pretty much just does what it does.

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