<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style>
#div1{
width: 100px;
height: 100px;
background: red;
position: absolute;
z-index: 2;
}
#img1{
position: absolute;
left: 500px;
top: 200px;
width: 200px;
height: 200px;
}
</style>
<script>
window.onload=function(){
var oDiv=document.getElementById("div1");
var oImg=document.getElementById("img1");
drag(oDiv);
function drag(obj){
obj.onmousedown = function(ev){
var ev = ev || event;
var disX = ev.clientX - this.offsetLeft;
var disY = ev.clientY - this.offsetTop;
if(obj.setCapture){
obj.setCapture();
}
document.onmousemove = function(ev){
var ev = ev || event;
var L = ev.clientX-disX;
var T = ev.clientY-disY;
var L1=L;
var R1=L+obj.offsetWidth;
var T1=T;
var B1=T+obj.offsetHeight;
var L2=oImg.offsetLeft;
var R2=L2+oImg.offsetWidth;
var T2=oImg.offsetTop;
var B2=T2+oImg.offsetHeight;
if(R1<L2 || L1>R2 || B1<T2 || T1>B2){
oImg.src="img/1.jpg";
}else{
oImg.src="img/2.jpg";
}
obj.style.left = L + "px";
obj.style.top = T + "px";
}
document.onmouseup = function(){
document.onmousemove=document.onmouseup=null;
if(obj.releaseCapture){
obj.releaseCapture();
}
}
return false;
}
}
}
</script>
</head>
<body>
<div id="div1"></div>
<img src="img/1.jpg" id="img1" />
</body>
</html>
