img-rounded 添加 border-radius:6px 來獲得圖片圓角
img-circle 添加 border-radius:50% 來讓整個圖片變成圓形
img-thumbnail 添加一些內(nèi)邊距（padding）和一個灰色的邊框
img-responsive 圖片響應(yīng)式

1、img-rounded

<!doctype html> 
<html lang="en"> 
<head> 
  <!--網(wǎng)站編碼格式，UTF-8 國際編碼，GBK或 gb2312 中文編碼--> 
  <meta http-equiv="content-type" content="text/html;charset=utf-8" /> 
  <meta http-equiv="X-UA-Compatible" content="IE=edge"> 
  <meta name="Keywords" content="關(guān)鍵詞一，關(guān)鍵詞二"> 
  <meta name="Description" content="網(wǎng)站描述內(nèi)容"> 
  <meta name="Author" content="Yvette Lau"> 
  <meta name = "viewport" content = " width = device-width, initial-scale = 1 "> 
  <title>BootstrapDemo</title> 
  <!--css js 文件的引入--> 
  <link rel="stylesheet" type="text/css" href="../bootstrap-3.3.5-dist/css/bootstrap.min.css"> 
</head> 
  <body style="padding: 20px;"> 
    <div class = "container"> 
      <img src = "5.jpg" class="img-rounded" >    
    </div> 
  </body> 
</html>

.img-rounded{border-radius:6px;}

效果：

2、img-circle

<body style="padding: 20px;"> 
  <div class = "container"> 
    <img src = "5.jpg" class="img-circle" >    
  </div> 
</body>

.img-circle{border-radius:50%;}

效果(因為本圖片的寬高大小不同，所以呈現(xiàn)出橢圓，如果將width和height設(shè)置相同，那么會呈現(xiàn)出一個圓)：

3、img-thumbnail

<body style="padding: 20px;"> 
  <div class = "container"> 
    <img src = "5.jpg" class="img-thumbnail" >  
    <img src = "4.jpg" class="img-thumbnail" >  
    <img src = "3.jpg" class="img-thumbnail" >  
  </div> 
</body>

.img-thumbnail{display:inline-block;max-width:100%;height:auto;padding:4px;line-height:1.42857143;
background-color:#FFF;border:1px solid #DDD;border-radius:4px;transition:all 0.2s ease-in-out;}

效果：

4、img-responsize

<body style="padding: 20px;"> 
  <div class = "container" style = "width:150px;"> 
    <img src = "5.jpg" class="img-responsive" width="400px" >    
  </div> 
</body>

.img-responsive{display:block;max-width:100%;height:auto;}

效果(img中的width屬性值被忽略)：