//Task
public void DoWork()
        {
            //Bitmap Array of tiles (Tiles = 3)
            Bitmap[] splits = new Bitmap[tiles];

            //Bitmap for the Screenshot
            var screenshot = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height, PixelFormat.Format32bppArgb);

            //Puffer Bitmap
            Bitmap buffer = new Bitmap(screenshot.Width,screenshot.Height);

            //Calc tile size
            int tilesize = screenshot.Width / tiles;

            // Create a graphics object from the bitmap.
            var gfxScreenshot = Graphics.FromImage(screenshot);
            while (isStarted)
            {
                // Take the screenshot from the upper left corner to the right bottom corner.
                gfxScreenshot.CopyFromScreen(Screen.PrimaryScreen.Bounds.X, Screen.PrimaryScreen.Bounds.Y, 0, 0, Screen.PrimaryScreen.Bounds.Size, CopyPixelOperation.SourceCopy);

                // Use graphics object from buffer to draw tiles on
                using (Graphics g = Graphics.FromImage(buffer)) //Throws System.InvalidOperationException: "Das Objekt wird bereits an anderer Stelle verwendet." when touching the window
                {
                    for (int i = 0; i < tiles; i++)
                    {
                        //Calculate dimensions for each tile
                        Rectangle r = new Rectangle(tilesize * i, 0, tilesize, screenshot.Height);

                        //Copy pixels to bitmap array
                        splits[i] = screenshot.Clone(r, PixelFormat.Format32bppArgb); //If code gets this far without System.InvalidOperationException it will throw a SystemOutOfMemoryException when over 4Gb.

                        //Draw result onto buffer
                        g.FillRectangle(
                            new SolidBrush(
                                ProcessBitmap(splits[i])) //returns a color
                            ,r);
                    }

                }
                //buffer.Save("Test.png", ImageFormat.Png);
                this.Invoke((MethodInvoker)delegate
                {
                    ImageBox.Image = buffer;
                });
            }
        }