图片放大后模糊，请高手帮忙？

        PicTemp.Image = Frm_main.PictureBox2.Image
        Dim SngPer As Single = 4 '放大或缩小的比例
        Dim PicNew As New System.Drawing.Bitmap(PicTemp.Image, PicTemp.Width * SngPer, PicTemp.Height * SngPer)
        PictureBox2.Image = PicNew