title: In GNOME/gdk/gtkmm/cairo, a equivalent series of codes for MS Windows "TransparentBlt()"?
body: <p>How can I port MFC</p>
  <pre><code>TotalDC.TransparentBlt(position.x, position.y, width, height, &amp;image1DC, 0, 0, width, height, RGB(255, 255, 255));
  </code></pre>
  <p>to GNOME/gdk/gtkmm/cairo?</p>
  <p>I know that MFC &quot;BitBlt();&quot; can be ported using</p>
  <pre><code>image1-&gt;copy_area(0,0,width,height,Total,position.x,position.y);
  </code></pre>
  <p>But this function does not designate the transparent RGB(r,g,b).</p>