Resize tiff and keep transparency and C #

Question

I am trying to resize an 8-bit TIF RGB and maintain its transparency in C #. I tried the following code.

using (Image thumbnail = new Bitmap(1500, 1500))
{
  using (Bitmap source = new Bitmap(@"c:\trans.tif"))
  {
    using (Graphics g = Graphics.FromImage(thumbnail))
    {
      g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
      g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
      g.Clear(Color.Transparent);
      g.DrawImage(source, 0, 0, 1500, 1500);

    }
  }
  thumbnail.Save(@"c:\testoutput.tif", ImageFormat.Tiff);
  //using (MemoryStream ms = new MemoryStream())
  //{
  //    //thumbnail.Save(ms, ImageFormat.Tiff);
  //    //
  //    //result = ms.ToArray();
  //}
}

The image was created using Photoshop, and I can’t understand why it does not hold the transparency on the resized.

Any ideas?

Answer 1

I really found out that due to how transparency is stored in tiff format using Photoshop, it was better to create png by automating photoshop and then crunching the resulting png.

Answer 2

you need to install pixelformat when you upgrade Image thumbnailto at least 32bpp argb:

new Bitmap(1500, 1500, PixelFormat.Format32bppPArgb)

Edit:

, source, , , using s