本文實例講述了JS圖片等比例縮放方法。分享給大家供大家參考，具體如下：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>javascript自動按比例顯示圖片，按比例壓縮圖片顯示</title>
<script type="text/javascript">
function AutoResizeImage(maxWidth,maxHeight,objImg){
var img = new Image();
img.src = objImg.src;
var hRatio;
var wRatio;
var Ratio = 1;
var w = img.width;
var h = img.height;
wRatio = maxWidth / w;
hRatio = maxHeight / h;
if (maxWidth ==0 && maxHeight==0){
Ratio = 1;
}else if (maxWidth==0){//
if (hRatio<1) Ratio = hRatio;
}else if (maxHeight==0){
if (wRatio<1) Ratio = wRatio;
}else if (wRatio<1 || hRatio<1){
Ratio = (wRatio<=hRatio?wRatio:hRatio);
}
if (Ratio<1){
w = w * Ratio;
h = h * Ratio;
}
objImg.height = h;
objImg.width = w;
}
</script>
</head>
<body>
<br />
<img src="1.jpg"
border="0"
width="0"
height="0"
onload="AutoResizeImage(100,0,this)"
/>
width:100px
<br />
<br />
<img src="1.jpg"
border="0"
width="0"
height="0"
onload="AutoResizeImage(0,100,this)"
/>
height:100px
<br />
<br />
<img src="1.jpg"
border="0"
width="0"
height="0"
onload="AutoResizeImage(100,100,this)"
/>
width:100px height:100px
<br />
<br />
<br />
<br />
<br />
<br />
<br />
</body>
</html>
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希望本文所述對大家JavaScript程序設計有所幫助。