title: rmagick is there a way to convert image in memory
body: <p>From <code>Rmagick</code> guide:</p>
  
  <p>Converting an image to another format</p>
  
  <p>Converting an image to another format is as simple as writing the
   image to a file.</p>
  
  <p>ImageMagick uses the output filename <code>suffix (".jpg"
   for JPEG, ".gif" for GIF, for example)</code> or <code>prefix ("ps:" for
   PostScript, for example)</code> to determine the format of the output image.</p>
  
  <p>Is there a way to convert image in memory?</p>