<body>
<div id="div1"></div>
<img src="1.jpg" id="img1" />
</body>
<style>
#div1 {width: 100px; height: 100px; background: red; position: absolute; z-index: 2;}
#img1 { position: absolute; left: 500px; top: 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 = '1.jpg';
} else {
oImg.src = '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>
