Use Graphic.DrawLines(Pen pen, Points points) for Metafile, the picture can not open when the count of points is large.

Hi guys,

I have a problem with a GDI+ metafile. I want to save a metafile by graphic. It works well when the point count is 10000 and the saved metafile can be opened. But when the point count is large (e.g. count = 100000), the metafile cannot be opened by mspaint.exe.

Is metafile record size limited? By the way, drawrectangles also has this issue.

Please have a look the following codes.

private void button1_Click(object sender, EventArgs e)
		{
			int width = 1489;
			int height = 471;

			Graphics offScreenBufferGraphics;
			Metafile m;
			using (MemoryStream stream = new MemoryStream())
			{
				using (offScreenBufferGraphics = Graphics.FromHwndInternal(IntPtr.Zero))
				{
					IntPtr deviceContextHandle = offScreenBufferGraphics.GetHdc();
					m = new Metafile(
					stream,
					deviceContextHandle,
					new RectangleF(0, 0, width, height),
					MetafileFrameUnit.Pixel,
					EmfType.EmfPlusOnly);
					offScreenBufferGraphics.ReleaseHdc();
				}
			}

			using (Graphics g = Graphics.FromImage(m))
			{
				// Set everything to high quality
				g.SmoothingMode = SmoothingMode.HighQuality;
				g.InterpolationMode = InterpolationMode.HighQualityBicubic;
				g.PixelOffsetMode = PixelOffsetMode.HighQuality;
				g.CompositingQuality = CompositingQuality.HighQuality;

				MetafileHeader metafileHeader = m.GetMetafileHeader();
				g.ScaleTransform(
				  metafileHeader.DpiX / g.DpiX,
				  metafileHeader.DpiY / g.DpiY);

				g.PageUnit = GraphicsUnit.Pixel;
				g.SetClip(new RectangleF(0, 0, width, height));

				// clears the image and colors the entire background
				g.Clear(Color.White);

				// draw lines
				using (Pen pen = new Pen(Color.Black, 1f))
				{
					 Random rnd = new Random(DateTime.Now.Millisecond);
					 List<PointF> polyPoints = new List<PointF>();
					 const int count = 10000;
					 for (int i = 1; i <= count; i++)
					 {
						 polyPoints.Add(new PointF(rnd.Next(1000),rnd.Next(1000)));
					 }
					 g.DrawLines(pen, polyPoints.ToArray());
					 // while
				} // using
			} // using

			// Get a handle to the metafile
			IntPtr iptrMetafileHandle = m.GetHenhmetafile();

			// Export metafile to an image file
			CopyEnhMetaFile(iptrMetafileHandle, @"F:\CacheToDisk\test2.emf");

			// Delete the metafile from memory
			DeleteEnhMetaFile(iptrMetafileHandle);
		}

		[DllImport("gdi32.dll")]
		static extern IntPtr CopyEnhMetaFile(  // Copy EMF to file
		  IntPtr hemfSrc,   // Handle to EMF
		  String lpszFile // File
		);

		[DllImport("gdi32.dll")]
		static extern int DeleteEnhMetaFile(  // Delete EMF
		  IntPtr hemf // Handle to EMF
		);
    }