js图片等比例缩放

<script language="JavaScript" type="text/javascript">
function DrawImage(ImgD,FitWidth,FitHeight)
{
var image=new Image();
image.src=ImgD.src;
if(image.width>0 && image.height>0)
{
if(image.width/image.height>= FitWidth/FitHeight)
{
if(image.width>FitWidth)
{
ImgD.width=FitWidth;
ImgD.height=(image.height*FitWidth)/image.width;
}
else
{
ImgD.width=image.width;
ImgD.height=image.height;
}
}
else
{
if(image.height>FitHeight)
{
ImgD.height=FitHeight;
ImgD.width=(image.width*FitHeight)/image.height;
}
else
{
ImgD.width=image.width;
ImgD.height=image.height;
}
}
}
}
</script>
<img src="asfds.jpg" />
<img src="asfds.jpg" alt="自动缩放后的效果" onload="javascript:DrawImage(this,300,200);" />

原图：



效果图：