根据屏幕大小，加载不同大小的图片_html/css_WEB-ITnose
引言今天要介绍的东西，很简单，但是对于前端响应式的时候是个很重要的知识；我们在用bootstrap这类前端框架时，虽然页面局部通过media query实现了，页面始终无滚动条，响应式页面。但是，bootstrap里面的img-responsive类只是通过设置图片100%，并没有真正的实现在手机上和电脑端加载不同大小的图片。
代码其实很简单
<!DOCTYPE html><html><head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width,initial-scale=1"> <title>Document</title> <script> document.createElement( "picture" ); </script></head><body> <picture> <source srcset="pic1.png" media="(max-width: 600px)"> <source srcset="pic2.png" media="(max-width: 800px)"> <img srcset="pic3.png" alt="pic"> </picture></body></html>
下面是在浏览器中的结果，我们打开Chrome浏览器，按f12后查看网络请求。
首先是三张图片
pic1.png
默认情况下，屏幕全屏，宽度大于800
pic2.png
当页面宽度在600px-800px（(600,800]）之间时
pic3.png
最后是页面小于等于600px
pic4.png
针对上面的代码，我们解释一下：其中的img元素是默认情况下显示的图片源，在其上面的两个source元素则是在特定媒体查询（media queries）条件下显示的图片。
这样我们只需要通过像写熟悉的css的媒体查询一样写代码，就能实现根据浏览器窗口大小，动态加载图片。在手机上，就不用加载一个电脑端才显示的大图。
GitHub上有位大神，基于以上的原则，编写了一个picfill的项目，大家有兴趣的可以去git上查看。
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