title: libpng not linked on Mac OSX 10.9.2
body: <p>I installed matrix2png on my Mac and had used it without problem before last week when I installed another image manipulating tool "circos". Circos requires me to install a different version of libpng, and I did. After that, I am no longer able to run matrix2png, which gives me the following error. I think the old ligpnb is not linked any more. Does anyone know how to fix this error? - appreciate your help.</p>
  
  <pre><code>dyld: Library not loaded: /usr/local/lib/libpng15.15.dylib
    Referenced from: /usr/local/bin/matrix2png
    Reason: image not found
  </code></pre>