function setImgSize(img,width,height){ 
var MaxWidth=width;//设置图片宽度界限 
var MaxHeight=height;//设置图片高度界限 
var HeightWidth=img.offsetHeight/img.offsetWidth;//设置高宽比 
var WidthHeight=img.offsetWidth/img.offsetHeight;//设置宽高比 
if(img.offsetWidth>MaxWidth){ 
img.width=MaxWidth; 
img.height=MaxWidth*HeightWidth; 
} 
if(img.offsetHeight>MaxHeight){ 
img.height=MaxHeight; 
img.width=MaxHeight*WidthHeight; 
} 
}
function setBigImg(img,width,height){ 
var MaxWidth=width;//设置图片宽度界限 
var MaxHeight=height;//设置图片高度界限 
var HeightWidth=img.offsetHeight/img.offsetWidth;//设置高宽比 
var WidthHeight=img.offsetWidth/img.offsetHeight;//设置宽高比 
if(img.offsetWidth>MaxWidth){ 
img.width=MaxWidth; 
img.height=MaxWidth*HeightWidth; 
} 
if(img.offsetHeight>MaxHeight){ 
img.height=MaxHeight; 
img.width=MaxHeight*WidthHeight; 
} 
}

//图片等比例缩放

//var FitWidth = 700;  //图片宽度
//var FitHeight = 400; //图片高度
function ResizePic(ImgTag,FitWidth,FitHeight)
{
    var image = new Image();
 image.src = ImgTag.src;
 if(image.width>0 && image.height>0){
  if(image.width/image.height >= FitWidth/FitHeight){
   if(image.width > FitWidth){
    ImgTag.width = FitWidth;
    ImgTag.height = (image.height*FitWidth)/image.width;
   }
   else{ 
    ImgTag.width = image.width;
    ImgTag.height = image.height;
   }
  }
  else{
   if(image.height > FitHeight){
    ImgTag.height = FitHeight;
    ImgTag.width = (image.width*FitHeight)/image.height;
   }
   else{
    ImgTag.width = image.width; 
    ImgTag.height = image.height;
   }
  }
 }
}