js 图片等比例缩放代码

var scaleImage = function(o, w, h){ 
var img = new Image(); 
img.src = o.src; 
if(img.width >0 && img.height>0) 
{ 
if(img.width/img.height >= w/h) 
{ 
if(img.width > w) 
{ 
o.width = w; 
o.height = (img.height*w) / img.width; 
} 
else 
{ 
o.width = img.width; 
o.height = img.height; 
} 
o.alt = img.width + "x" + img.height; 
} 
else 
{ 
if(img.height > h) 
{ 
o.height = h; 
o.width = (img.width * h) / img.height; 
} 
else 
{ 
o.width = img.width; 
o.height = img.height; 
} 
o.alt = img.width + "x" + img.height; 
} 
} 
}

HTML

<div> 
<p><img src="../comment/img/max.jpg" onload="scaleImage(this,300,300)" alt="pic" /></p> 
<p><img src="../comment/img/2.jpg" onload="scaleImage(this,300,300)" /></p> 
<p><img src="../comment/img/3.jpg" onload="scaleImage(this,300,300)" /></p> 
<p><img src="../comment/img/4.jpg" onload="scaleImage(this,300,300)" /></p> 
</div>