WPF实现图片合成或加水印的方法【2种方法】

private BitmapSource MakePicture(string bgImagePath,string headerImagePath,string signature)
{
  //获取背景图
  BitmapSource bgImage = new BitmapImage(new Uri(bgImagePath,UriKind.Relative));
  //获取头像
  BitmapSource headerImage = new BitmapImage(new Uri(headerImagePath,UriKind.Relative));
  //创建一个RenderTargetBitmap 对象，将WPF中的Visual对象输出
  RenderTargetBitmap composeImage = new RenderTargetBitmap(bgImage.PixelWidth,bgImage.PixelHeight,bgImage.DpiX,bgImage.DpiY,PixelFormats.Default);
  FormattedText signatureTxt = new FormattedText(signature,System.Globalization.CultureInfo.CurrentCulture,System.Windows.FlowDirection.LeftToRight,new Typeface(System.Windows.SystemFonts.MessageFontFamily,FontStyles.Normal,FontWeights.Normal,FontStretches.Normal),50,System.Windows.Media.Brushes.White);
  DrawingVisual drawingVisual = new DrawingVisual();
  DrawingContext drawingContext = drawingVisual.RenderOpen();
  drawingContext.DrawImage(bgImage,new Rect(0,bgImage.Width,bgImage.Height));
  //计算头像的位置
  double x = (bgImage.Width / 2 - headerImage.Width) / 2;
  double y = (bgImage.Height - headerImage.Height) / 2 - 100;
  drawingContext.DrawImage(headerImage,new Rect(x,y,headerImage.Width,headerImage.Height));
  //计算签名的位置
  double x2 = (bgImage.Width/2 - signatureTxt.Width) / 2;
  double y2 = y + headerImage.Height + 20;
  drawingContext.DrawText(signatureTxt,new System.Windows.Point(x2,y2));
  drawingContext.Close();
  composeImage.Render(drawingVisual);
  //定义一个JPG编码器
  JpegBitmapEncoder bitmapEncoder = new JpegBitmapEncoder();
  //加入第一帧
  bitmapEncoder.Frames.Add(BitmapFrame.Create(composeImage));
  //保存至文件（不会修改源文件，将修改后的图片保存至程序目录下）
  string savePath = System.AppDomain.CurrentDomain.SetupInformation.ApplicationBase + @"合成.jpg";
  bitmapEncoder.Save(File.OpenWrite(Path.GetFileName(savePath)));
  return composeImage;
}

private BitmapSource MakePictureGDI(string bgImagePath,string signature)
{
  GDI.Image bgImage = GDI.Bitmap.FromFile(bgImagePath);
  GDI.Image headerImage = GDI.Bitmap.FromFile(headerImagePath);
  //新建一个画板，画板的大小和底图一致
  System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(bgImage.Width,bgImage.Height);
  System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
  //设置高质量插值法
  g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
  //设置高质量,低速度呈现平滑程度
  g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
  //清空画布并以透明背景色填充
  g.Clear(System.Drawing.Color.Transparent);
  //先在画板上面画底图
  g.DrawImage(bgImage,new GDI.Rectangle(0,bitmap.Width,bitmap.Height));
  //再在画板上画头像
  int x = (bgImage.Width / 2 - headerImage.Width) / 2;
  int y = (bgImage.Height - headerImage.Height) / 2 - 100;
  g.DrawImage(headerImage,new GDI.Rectangle(x,headerImage.Height),GDI.GraphicsUnit.Pixel);
  //在画板上写文字
  using (GDI.Font f = new GDI.Font("Arial",20,GDI.FontStyle.Bold))
  {
    using (GDI.Brush b = new GDI.SolidBrush(GDI.Color.White))
    {
      float fontWidth = g.MeasureString(signature,f).Width;
      float x2 = (bgImage.Width / 2 - fontWidth) / 2;
      float y2 = y + headerImage.Height + 20;
      g.DrawString(signature,f,b,x2,y2);
    }
  }
  try
  {
    string savePath = System.AppDomain.CurrentDomain.SetupInformation.ApplicationBase + @"GDI+合成.jpg";
    bitmap.Save(savePath,System.Drawing.Imaging.ImageFormat.Jpeg);
    return ToBitmapSource(bitmap);
  }
  catch (System.Exception e)
  {
    throw e;
  }
  finally
  {
    bgImage.Dispose();
    headerImage.Dispose();
    g.Dispose();
  }
}
#region GDI+ Image 转化成 BitmapSource
[System.Runtime.InteropServices.DllImport("gdi32")]
static extern int DeleteObject(IntPtr o);
public BitmapSource ToBitmapSource(GDI.Bitmap bitmap)
{
  IntPtr ip = bitmap.GetHbitmap();
  BitmapSource bitmapSource = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(
    ip,IntPtr.Zero,System.Windows.Int32Rect.Empty,System.Windows.Media.Imaging.BitmapSizeOptions.FromEmptyOptions());
  DeleteObject(ip);//释放对象
  return bitmapSource;
}
#endregion