<script language="javascript">

var flag=false;

function DrawImage(ImgD){

var image=new Image();

image.src=ImgD.src;

if(image.width>0 && image.height>0){

flag=true;

if(image.width/image.height>=500/400){

if(image.width>500){

ImgD.width=500;

ImgD.height=(image.height*500)/image.width;

}else{

ImgD.width=image.width;

ImgD.height=image.height;

}

}

else{

if(image.height>400){

ImgD.height=400;

ImgD.width=(image.width*400)/image.height;

}else{

ImgD.width=image.width;

ImgD.height=image.height;

}

}

}

}

</script>

调用方式（img是显示图片的html代 ） <IMG src= "temp.jpg" border=0 onload="javascript：DrawImage(this);">

修改后：

<script language="javascript">

var flag=false; //控制小图

function DrawImage(ImgD,maxwidth,maxheight){

var image=new Image();

image.src=ImgD.src;

if(image.width>0 && image.height>0){

flag=true;

if(image.width/image.height>=maxwidth/maxheight){

if(image.width>maxwidth){

ImgD.width=maxwidth;

ImgD.height=(image.height*maxwidth)/image.width;

}else{

ImgD.width=image.width;

ImgD.height=image.height;

}

}

else{

if(image.height>maxheight){

ImgD.height=maxheight;

ImgD.width=(image.width*maxheight)/image.height;

}else{

ImgD.width=image.width;

ImgD.height=image.height;

}

}

}

}

</script>

呵呵，多了两个参数，也就是你能够接受的最大宽度maxwidth与最大高度maxheight

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