圖片加水印

 /// 圖片加水印文字
        /// </summary>
        /// <param name="oldpath">舊圖片地址</param>
        /// <param name="text">水印文字</param>
        /// <param name="newpath">新圖片地址</param>
        /// <param name="Alpha">透明度</param>
        /// <param name="fontsize">字體大小</param>
        public  void AddWaterText(string oldpath, string text, string newpath, int Alpha, int fontsize)
        {
            try
            {
                text = text + "版權所有";
                FileStream fs = new FileStream(oldpath, FileMode.Open);
                BinaryReader br = new BinaryReader(fs);
                byte[] bytes = br.ReadBytes((int)fs.Length);
                br.Close();
                fs.Close();
                MemoryStream ms = new MemoryStream(bytes);


                System.Drawing.Image imgPhoto = System.Drawing.Image.FromStream(ms);
                int imgPhotoWidth = imgPhoto.Width;
                int imgPhotoHeight = imgPhoto.Height;


                Bitmap bmPhoto = new Bitmap(imgPhotoWidth, imgPhotoHeight, System.Drawing.Imaging.PixelFormat.Format24bppRgb);


                bmPhoto.SetResolution(72, 72);
                Graphics gbmPhoto = Graphics.FromImage(bmPhoto);
                //gif背景色
                gbmPhoto.Clear(Color.FromName("white"));
                gbmPhoto.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
                gbmPhoto.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                gbmPhoto.DrawImage(imgPhoto, new Rectangle(0, 0, imgPhotoWidth, imgPhotoHeight), 0, 0, imgPhotoWidth, imgPhotoHeight, GraphicsUnit.Pixel);
                System.Drawing.Font font = null;
                System.Drawing.SizeF crSize = new SizeF();
                font = new Font("宋體", fontsize, FontStyle.Bold);
                //測量指定區域
                crSize = gbmPhoto.MeasureString(text, font);
                float y = imgPhotoHeight - crSize.Height;
                float x = imgPhotoWidth - crSize.Width;
                System.Drawing.StringFormat StrFormat = new System.Drawing.StringFormat();
                StrFormat.Alignment = System.Drawing.StringAlignment.Center;


                //畫兩次製造透明效果
                System.Drawing.SolidBrush semiTransBrush2 = new System.Drawing.SolidBrush(Color.FromArgb(Alpha, 56, 56, 56));
                gbmPhoto.DrawString(text, font, semiTransBrush2, x + 1, y + 1);


                System.Drawing.SolidBrush semiTransBrush = new System.Drawing.SolidBrush(Color.FromArgb(Alpha, 176, 176, 176));
                gbmPhoto.DrawString(text, font, semiTransBrush, x, y);
                bmPhoto.Save(newpath, System.Drawing.Imaging.ImageFormat.Jpeg);
                gbmPhoto.Dispose();
                imgPhoto.Dispose();
                bmPhoto.Dispose();
            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

原文出處