รวมรูปภาพใน C#

using (Presentation pres = new Presentation())
{
    IPPImage image = pres.Images.AddImage(File.ReadAllBytes("imagepath1"));
    pres.Slides[0].Shapes.AddPictureFrame(ShapeType.Rectangle, 0, 0, 360, 540, image);

    IPPImage image2 = pres.Images.AddImage(File.ReadAllBytes("imagepath2"));
    pres.Slides[0].Shapes.AddPictureFrame(ShapeType.Rectangle, 360, 0, 360, 540, image2);

    pres.Slides[0].GetThumbnail(new Size(960, 720)).Save("merged-image.png", ImageFormat.Png);
}