Figure 2. The metafile image created by the example listing

After you create the new metafile, it is empty. You add drawing items to the metafile by creating a Graphics object based on it and then calling the Graphics object's drawing methods. The listing below gives an example with the output shown in Figure 2.

private void button1_Click(object sender, EventArgs e)
{
Graphics g = CreateGraphics();
IntPtr pHdc = g.GetHdc();
Metafile mf = new Metafile("c:\\test.emf", pHdc);
g.ReleaseHdc(pHdc);
g.Dispose();
g = Graphics.FromImage(mf);
g.DrawRectangle(Pens.Black, 10, 10, 390, 230);
g.FillRectangle(Brushes.Red, 20, 20, 370, 210);
g.FillEllipse(Brushes.Green, 160, 100, 100, 100);
Font f = new Font("Arial", 40);
g.DrawString("metafiles rule!", f, Brushes.Blue, 30, 40);
g.Dispose();
g = this.CreateGraphics();
g.DrawImage(mf,0,0);

Converting a Metafile to a Bitmap

If you have a metafile but need a bitmap, the conversion is easy; you cannot convert the other way, however. I won't go into the details, but the function given here, which is passed a metafile and returns a bitmap of the same image, shows you how its done.

Bitmap BitmapFromMetafile(Metafile mf)
{
g = this.CreateGraphics();
int BitmapWidth = (int)(g.DpiX * mf.Width / mf.HorizontalResolution);
int BitmapHeight = (int)(g.DpiY * mf.Height / mf.VerticalResolution);
Bitmap bmp = new Bitmap(BitmapWidth, BitmapHeight, g);
g.Dispose();
g = Graphics.FromImage(bmp);
g.DrawImage(mf, 0, 0, BitmapWidth, BitmapHeight);
g.Dispose();
return bmp;
}

Summary

Metafiles are one of two fundamental ways of representing an image. While they are not suitable for all images, photographs in particular, they have many advantages over bitmaps for charts and drawings.