DayPilot » Knowledge Base » Writing PNG to Response.OutputStream - System.Runtime.InteropServices.ExternalException: A generic error occurred in GDI+.

When you try to save a Bitmap in a PNG format directly to Response.OutputStream like this:

Bitmap bmp = DayPilotMonth1.ExportBitmap();
bmp.Save(Response.OutputStream, ImageFormat.Png);

You may get the following error:

System.Runtime.InteropServices.ExternalException: A generic error occurred in GDI+.

You can solve this problem by using a temporary MemoryStream:

// PNG requires random access to the output stream
using (MemoryStream mem = new MemoryStream())
{
  bmp.Save(mem, ImageFormat.Png);
  mem.WriteTo(Response.OutputStream);
}

Bitmap.Save() method requires random access to the output memory stream. This is not possible in case of a Response.OutputStream and an exception is thrown.