图像等比例缩放 等比例缩放图片

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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>= 164/112){ 
   if(image.width>164){
    ImgD.width=164; 
    ImgD.height=(image.height*164)/image.width; 
   }else{ 
    ImgD.width=image.width;
    ImgD.height=image.height; 
   } 
   ImgD.alt=image.width+"x"+image.height; 
  } 
  else{ 
   if(image.height>112){
    ImgD.height=112; 
    ImgD.width=(image.width*112)/image.height; 
   }else{ 
    ImgD.width=image.width;
    ImgD.height=image.height; 
   } 
   ImgD.alt=image.width+"x"+image.height; 
  } 
 }
}