/*
將某張圖片切成指定大小
*/
function DrawImage(ImgD,FitWidth,FitHeight)
{
    var image=new Image();
    image.src=ImgD.src;
    if(image.width>0 && image.height>0)
    {
        if(image.width/image.height>= FitWidth/FitHeight)
        {
            if(image.width>FitWidth)
            {
            ImgD.width=FitWidth;
            ImgD.height=(image.height*FitWidth)/image.width;
            }
            else
            {
            ImgD.width=image.width;
            ImgD.height=image.height;
            }
        }
        else
        {
            if(image.height>FitHeight)
            {
            ImgD.height=FitHeight;
            ImgD.width=(image.width*FitHeight)/image.height;
            }
            else
            {
            ImgD.width=image.width;
            ImgD.height=image.height;
            }
        }
    }
}