title: how to draw an image on a canvas with transparency/alpha
body: <p>hy there!</p>
  
  <p>i left out usings etc... just plain code:</p>
  
  <pre><code>var image = Image.FromFile(/* my magic source */);
  var bitmap = new Bitmap(image.Width, image.Height);
  var canvas = Graphics.FromImage(bitmap);
  var brush = new SolidBrush(/* my magic color */);
  canvas.FillRectangle(brush, 0, 0, image.Width, image.Height);
  canvas.DrawImage(image, new Rectangle(0, 0, image.Width, image.Height));
  canvas.Save();
  bitmap.Save(/* my magic target */);
  </code></pre>
  
  <p>i want to draw <code>image</code> with alpha 55% on <code>canvas</code>. <code>image</code> is a .png-file and uses transparency itself. (NOTE: i do not want to make <code>image.MakeTransparent()</code> - it is already transparent, i just need some alpha-effect)</p>
  
  <p>how can i achieve this?</p>