title: Cannot load PNG in C# on Mac OSX running Mono
body: <p>In C#, I'm trying to load a png file on Mac OSX using the latest Mono</p>
  
  <pre><code>using System.Drawing;
  Bitmap bmp = new Bitmap("test.png");
  </code></pre>
  
  <p>I get the following error</p>
  
  <pre><code>Either the image format is unknown or you don't have the required libraries to decode this format [GDI+ status: UnknownImageFormat]
  </code></pre>
  
  <p>It doesn't happen with all png files; just this one.
  <br><img src="https://i.stack.imgur.com/66EVS.png" alt="alt text"></p>
  
  <p>Resaving in photo shop doesn't fix it unless I switch to 8bpp.  Is there something I need to install to support this "special" png file?  Works fine on windows.</p>