When drawing an image: System.Runtime.InteropServices.ExternalException: A generic error occurred in GDI

Question

I\'ve got a global Graphics object created from a Panel. At regular intervals an image is picked up from the disk and drawn into the panel using Graphics.DrawImage(). It wor

Answer 1

Your problem is similar to what I thought, but not quite. When you are loading the image, you are loading it from a MemoryStream. You have to keep the stream open for the lifetime of the image, see MSDN Image.FromStream.

You must keep the stream open for the lifetime of the Image.

The solution is to make a copy of your image in the FromImage function:

private void LoadImage(string filename, ref Image image)
{
  using (MemoryStream memoryStream = DecryptImageBinary(Settings.Default.ImagePath + filename, _cryptPassword))
  {
      using (tmpImage = Image.FromStream(memoryStream))
      { 
         image = new Bitmap(tmpImage);
      }
  }

}

Similar to the dispose problem I mentioned, the image will seem to work and then randomly fail when the underlying stream is garbage collected.

Answer 2

Without a little more code there is not enough to properly diagnose here, however, one thing to look at is that you may have disposed on the image your a drawing with at some point earlier and it is only after the garbage collector runs that your code is failing. Are you using cloned images anywhere? One thing I was suprised to learn is that if you do a straight clone of an image, you are not cloning the underlying bitmap that the image rely's upon, only the image structure, to create a proper copy of an image you have to create a new image:

var newImage = new Bitmap(img)

as

var newImage = oldImg.Clone();
oldImg.Dispose();
...
gr.DrawImage(newImage, new Rectangle(0,0,newImage.Width,newImage.Height);

will work for a while, but then fail at some random point...