本文实例讲述了JavaScript实现图片的放大缩小及拖拽功能。分享给大家供大家参考，具体如下：
实现效果如下：
实现代码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
div{width:400px;height:400px;overflow:hidden;position:relative;border:1px solid #000;}
div img{position:absolute;height:100%;width:auto;cursor:move;}
</style>
</head>
<body>
<div id="div" onmousewheel="return bbimg(this)"><img id="img" border="0" src="img/zs.jpg" /></div>
<script language="javascript">
var params = {
zoomVal:1,
left: 0,
top: 0,
currentX: 0,
currentY: 0,
flag: false
};
//图片缩放
function bbimg(o){
var o=o.getElementsByTagName("img")[0];
params.zoomVal+=event.wheelDelta/1200;
if (params.zoomVal >= 0.2) {
o.style.transform="scale("+params.zoomVal+")";
} else {
params.zoomVal=0.2;
o.style.transform="scale("+params.zoomVal+")";
return false;
}
}
//获取相关CSS属性
var getCss = function(o,key){
return o.currentStyle? o.currentStyle[key] : document.defaultView.getComputedStyle(o,false)[key];
};
//拖拽的实现
var startDrag = function(bar, target, callback){
if(getCss(target, "left") !== "auto"){
params.left = getCss(target, "left");
}
if(getCss(target, "top") !== "auto"){
params.top = getCss(target, "top");
}
//o是移动对象
bar.onmousedown = function(event){
params.flag = true;
if(!event){
event = window.event;
//防止IE文字选中
bar.onselectstart = function(){
return false;
}
}
var e = event;
params.currentX = e.clientX;
params.currentY = e.clientY;
};
document.onmouseup = function(){
params.flag = false;
if(getCss(target, "left") !== "auto"){
params.left = getCss(target, "left");
}
if(getCss(target, "top") !== "auto"){
params.top = getCss(target, "top");
}
};
document.onmousemove = function(event){
var e = event ? event: window.event;
if(params.flag){
var nowX = e.clientX, nowY = e.clientY;
var disX = nowX - params.currentX, disY = nowY - params.currentY;
target.style.left = parseInt(params.left) + disX+ "px";
target.style.top = parseInt(params.top) + disY+ "px";
if (typeof callback == "function") {
callback((parseInt(params.left) || 0) + disX, (parseInt(params.top) || 0) + disY);
}
if (event.preventDefault) {
event.preventDefault();
}
return false;
}
}
};
startDrag(document.getElementById("img"),document.getElementById("img"))
</script>
</body>
</html>
希望本文所述对大家JavaScript程序设计有所帮助。
