# 放大镜功能
<!DOCTYPE html>
<html>
<head>
<title>放大镜</title>
<meta charset="utf-8">
<style type="text/css">
*{
margin: 0px;
padding: 0px;
}
body{
width: 960px;
margin:40px auto;
}
#small{
width: 300px;
height: 300px;
border:1px solid #eee;
border-radius: 4px;
position: relative;
}
#small img{
width: 100%;
height: 100%;
}
div {
float: left;
margin-right: 10px;
}
#big{
width: 300px;
height: 300px;
overflow: hidden;
position: relative;
border:1px solid #eee;
border-radius: 4px;
display: none;
}
#look_girl{
position: absolute;
left: 0px;
top:0px;
}
#move{
width: 100px;
height: 100px;
background:#000;
opacity: .5;
position: absolute;
display: none;
left: 0px;
top: 0px;
}
</style>
</head>
<body>
<div id="small">
<img src="apple.jpg">
<!-- 选择区域 -->
<p id="move"></p>
</div>
<div id="big">
<img src="apple.jpg" id="look_girl">
</div>
</body>
</html>
<script type="text/javascript">
var move = document.getElementById('move');
var small = document.getElementById('small');
var big = document.getElementById('big');
var look_girl = document.getElementById('look_girl');
small.onmousemove = function(event){
event = event || window.event;
this.style.cursor = 'move';
// 计算move移动块的left值
var move_left = event.clientX - this.offsetLeft - move.offsetWidth/2;
// 计算move移动块的top值
var move_top = event.clientY - this.offsetTop - move.offsetHeight/2;
// 超出左边界赋值为0
move_left = move_left < 0 ? 0 : move_left;
// 超出右边界赋值为盒子宽度-移动块的宽度
move_left = move_left > this.offsetWidth - move.offsetWidth ? this.offsetWidth - move.offsetWidth : move_left;
// 超出上边界赋值为0
move_top = move_top < 0 ? 0 : move_top;
// 超出下边界赋值为盒子高度-移动块高度
move_top = move_top > this.offsetHeight - move.offsetHeight ? this.offsetHeight - move.offsetHeight : move_top;
// 修改移动块left、top值
move.style.left = move_left + 'px';
move.style.top = move_top + 'px';
/*
计算图片需要移动的坐标
距离左边left 图片宽度 盒子宽度 距离左边left 图片宽度 盒子宽度
big_x/(look_girl.offsetWidth-big.offsetWidth) = move_left/(small.offsetWidth-move.offsetWidth);
big_y/(look_girl.offsetHeight-big.offsetHeight) = move_top/(small.offsetHeight-move.offsetHeight);
*/
var big_x = move_left/(small.offsetWidth-move.offsetWidth) * (look_girl.offsetWidth-big.offsetWidth);
var big_y = move_top/(small.offsetHeight-move.offsetHeight) * (look_girl.offsetHeight-big.offsetHeight);
// 修改图片定位
look_girl.style.left = -big_x + 'px';
look_girl.style.top = -big_y + 'px';
}
small.onmouseover = function(){
move.style.display = 'block';
big.style.display = 'block';
}
small.onmouseout = function(){
move.style.display = 'none';
big.style.display = 'none';
}
</script>
# 封装
可以封装后使用,稍微修改一下也可以支持vue、react magnifier传递四个参数，分别是包裹小图片的盒子，包裹大图片的盒子，放大区域，放大的局部图片
function magnifier(small,big,move,bigimg){
var move = document.getElementById(move);
var small = document.getElementById(small);
var big = document.getElementById(big);
var bigimg = document.getElementById(bigimg);
small.onmousemove = function(event){
event = event || window.event;
this.style.cursor = 'move';
// 计算move移动块的left值
var move_left = event.clientX - this.offsetLeft - move.offsetWidth/2;
// 计算move移动块的top值
var move_top = event.clientY - this.offsetTop - move.offsetHeight/2;
// 超出左边界赋值为0
move_left = move_left < 0 ? 0 : move_left;
// 超出右边界赋值为盒子宽度-移动块的宽度
move_left = move_left > this.offsetWidth - move.offsetWidth ? this.offsetWidth - move.offsetWidth : move_left;
// 超出上边界赋值为0
move_top = move_top < 0 ? 0 : move_top;
// 超出下边界赋值为盒子高度-移动块高度
move_top = move_top > this.offsetHeight - move.offsetHeight ? this.offsetHeight - move.offsetHeight : move_top;
// 修改移动块left、top值
move.style.left = move_left + 'px';
move.style.top = move_top + 'px';
var big_x = move_left/(small.offsetWidth-move.offsetWidth) * (bigimg.offsetWidth-big.offsetWidth);
var big_y = move_top/(small.offsetHeight-move.offsetHeight) * (bigimg.offsetHeight-big.offsetHeight);
// 修改图片定位
bigimg.style.left = -big_x + 'px';
bigimg.style.top = -big_y + 'px';
}
small.onmouseover = function(){
move.style.display = 'block';
big.style.display = 'block';
}
small.onmouseout = function(){
move.style.display = 'none';
big.style.display = 'none';
}
}
magnifier('small','big','move','apple')
# es6规则
export function magnifier(small,big,move,bigimg){
var move = document.getElementById(move);
var small = document.getElementById(small);
var big = document.getElementById(big);
var bigimg = document.getElementById(bigimg);
small.onmousemove = function(event){
event = event || window.event;
this.style.cursor = 'move';
// 计算move移动块的left值
var move_left = event.clientX - this.offsetLeft - move.offsetWidth/2;
// 计算move移动块的top值
var move_top = event.clientY - this.offsetTop - move.offsetHeight/2;
// 超出左边界赋值为0
move_left = move_left < 0 ? 0 : move_left;
// 超出右边界赋值为盒子宽度-移动块的宽度
move_left = move_left > this.offsetWidth - move.offsetWidth ? this.offsetWidth - move.offsetWidth : move_left;
// 超出上边界赋值为0
move_top = move_top < 0 ? 0 : move_top;
// 超出下边界赋值为盒子高度-移动块高度
move_top = move_top > this.offsetHeight - move.offsetHeight ? this.offsetHeight - move.offsetHeight : move_top;
// 修改移动块left、top值
move.style.left = move_left + 'px';
move.style.top = move_top + 'px';
var big_x = move_left/(small.offsetWidth-move.offsetWidth) * (bigimg.offsetWidth-big.offsetWidth);
var big_y = move_top/(small.offsetHeight-move.offsetHeight) * (bigimg.offsetHeight-big.offsetHeight);
// 修改图片定位
bigimg.style.left = -big_x + 'px';
bigimg.style.top = -big_y + 'px';
}
small.onmouseover = function(){
move.style.display = 'block';
big.style.display = 'block';
}
small.onmouseout = function(){
move.style.display = 'none';
big.style.display = 'none';
}
}
# 引入
import {magnifier} from '../../static/js/test.js'
magnifier('small','big','move','apple')