//不失真加载图片
function imgZoomer(imgObj,canvas_width,canvas_height){
    var obj = imgObj;
    var src_width = GetImageWidth(obj);
    var src_height =GetImageHeight(obj);
    var widthScale =  src_width / canvas_width;
	  var heightScale = src_height / canvas_height;
  
    if (widthScale >= 1 || heightScale >= 1) {
      //哪边差的小，以哪边为基准放大
      if (widthScale < heightScale) {
        obj.width = src_width / heightScale;
        obj.height = canvas_height;
      } else {
        obj.width = canvas_width;
        obj.height = src_height / widthScale;
      }
    }else {
        obj.width = src_width;
        obj.height = src_height;
    }
}
var OriginImage=new Image();
function GetImageWidth(oImage){
  if(OriginImage.src!=oImage.src)OriginImage.src=oImage.src;
  return OriginImage.width;
}

function GetImageHeight(oImage){
  if(OriginImage.src!=oImage.src)OriginImage.src=oImage.src;
  return OriginImage.height;
}