css把图片缩小的方法：可以通过设置图片的width或者height属性来实现图片的宽度高度，从而将图片缩小，比如在css中添加“width:300pxheight:200px”样式代码将图片设置成宽度300px、高度200px大小，如需缩小将属性值减少即可。
涉及到 CSS3 的动画（animation）、2D 转换（transform: scale），具体如代码所示。[html] view plain copy
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/htmlcharset=utf-8" />
<title>无标题文档</title>
<style>
@keyframes warn {
0% {
transform: scale(0)
opacity: 0.0
}
25% {
transform: scale(0)
opacity: 0.1
}
50% {
transform: scale(0.1)
opacity: 0.3
}
75% {
transform: scale(0.5)
opacity: 0.5
}
100% {
transform: scale(1)
opacity: 0.0
}
}
@-webkit-keyframes "warn" {
0% {
-webkit-transform: scale(0)
opacity: 0.0
}
25% {
-webkit-transform: scale(0)
opacity: 0.1
}
50% {
-webkit-transform: scale(0.1)
opacity: 0.3
}
75% {
-webkit-transform: scale(0.5)
opacity: 0.5
}
100% {
-webkit-transform: scale(1)
opacity: 0.0
}
}
.container {
position: relative
width: 40px
height: 40px
border: 1px solid #000
}
/* 保持大小不变的小圆圈 */
.dot {
position: absolute
width: 6px
height: 6px
left: 15px
top: 15px
-webkit-border-radius: 20px
-moz-border-radius: 20px
border: 2px solid red
border-radius: 20px
z-index: 2
}
/* 产生动画（向外扩散变大）的圆圈 */
.pulse {
position: absolute
width: 24px
height: 24px
left: 2px
top: 2px
border: 6px solid red
-webkit-border-radius: 30px
-moz-border-radius: 30px
border-radius: 30px
z-index: 1
opacity: 0
-webkit-animation: warn 3s ease-out
-moz-animation: warn 3s ease-out
animation: warn 3s ease-out
-webkit-animation-iteration-count: infinite
-moz-animation-iteration-count: infinite
animation-iteration-count: infinite
}
</style>
</head>
<body>
<div class="container">
<div class="dot"></div>
<div class="pulse"></div>
</div>
</body>
</html>
