Need basic structure for loop drawing in picturebox.

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I am looking for an efficient structure for drawing graphics to a bitmap in memory, and then drawing it to the picturebox on my WinForm. I am using a timer event so that it will draw many times a second.I will show relevant code that I have been using below:

These are defined in the beginning:

private System.Timers.Timer mainTimer = new System.Timers.Timer();
private double fps = 10.0;
mainTimer.Elapsed += new System.Timers.ElapsedEventHandler(MainLoop);
mainTimer.Interval = 1000.0 / fps;
mainTimer.Enabled = true;

After that I have drawing code in my main loop. Note, this is just for testing at present:

private void MainLoop()
{
Rectangle rectImg = new Rectangle(0, 0, picbox_width, picbox_height);
Bitmap memImg = new Bitmap(picbox_width, picbox_height);
memImg.SetResolution(hres, vres); // Resolution values from backgroundImg
using (Graphics g = Graphics.FromImage(memImg))
{
using(ImageAttributes wrapMode = new ImageAttributes())
{
wrapMode.SetWrapMode(System.Drawing.Drawing2D.WrapMode.TileFlipXY);
g.DrawImage(backgroundImg, rectImg, 0, 0, 100, 100, GraphicsUnit.Pixel, wrapMode);
}
g.DrawPolygon(borderColor, polygonPoints); // Parameters defined elsewhere.
MyPictureBox.BackgroundImage = memImg;
}
}

One of the problems I am facing is that I get an error on line 12. The error is as follows:

Exception User-Unhandled

System.InvalidOperationException: 'Object is currently in use elsewhere.'

I have read that it is possibly an error with threading and that I need to use a BeginInvoke method to solve the problem. My main questions are do I need the BeginInvoke on each of my graphics calls, or is there a simpler format I could use (for any of my above code) to make it more straightforward and efficient?

Please note that there may be some code spelling errors, as the computer I code on is not allowed an Internect connection or to have any storage connected, so I am copying it the best I can. School rules :P

2 Replies

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Mario Scheeren7y ago
Accepted answer
private void MainLoop()
{
  Rectangle rectImg = new Rectangle(0, 0, picbox_width, picbox_height);
  Bitmap memImg = new Bitmap(picbox_width, picbox_height);
  memImg.SetResolution(hres, vres);  // Resolution values from backgroundImg

  using (Graphics g = Graphics.FromImage(memImg))
  {
    using(ImageAttributes wrapMode = new ImageAttributes())
    {
      wrapMode.SetWrapMode(System.Drawing.Drawing2D.WrapMode.TileFlipXY);
      using (Bitmap tmp = (Bitmap)backgroundImg.Clone())
      {
       g.DrawImage(tmp, rectImg, 0, 0, 100, 100, GraphicsUnit.Pixel, wrapMode);
      }
    }
    g.DrawPolygon(borderColor, polygonPoints); // Parameters defined elsewhere.
  }
MyPictureBox.BackgroundImage = memImg;
}
+2
Mario Scheeren7y ago
Hi, I bet your error occurs bc the image is in use somewhere else ( being drawn, whatever ). That means Invoking won't help anything. Where does this image come from? Is it maybe being displayed in a picturebox or something like that?
Simply try cloning ((Bitmap)image.Clone()) it - otherwise load it in another variable ( not the reference, a new instance )
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