图片按比例缩放函数
<script language="JavaScript"><!--//图片按比例缩放var flag=false;function DrawImage(ImgD,iwidth,iheight){//参数(图片,允许的宽度,允许的高度)var image=new Image();image.src=ImgD.src;if(image.width>0 && image.height>0){flag=true;if(image.width/image.height>= iwidth/iheight){if(image.width>iwidth){ ImgD.width=iwidth;ImgD.height=(image.height*iwidth)/image.width;}else{ImgD.width=image.width; ImgD.height=image.height;}ImgD.alt=image.width+"×"+image.height;}else{if(image.height>iheight){ ImgD.height=iheight;ImgD.width=(image.width*iheight)/image.height; }else{ImgD.width=image.width; ImgD.height=image.height;}ImgD.alt=image.width+"×"+image.height;}}} //--></script>调用：<img src="images/toplogo.gif" onload="javascript:DrawImage(this,100,100)">详细出处参考：http://www.jb51.net/article/175.htm