title: imagemagick: create a .png file which is just a solid rectangle
body: <p>I want to create a .png file which is just a solid color.</p>
  
  <p>This must be easy to do using ImageMagick but I can't figure out the problem:</p>
  
  <pre><code>C:\tmp&gt;convert -size 8x16 -stroke black -fill black -draw "rectangle 0,0,8,16" black.png
  Magick: missing an image filename `black.png' @ error/convert.c/ConvertImageComm
  and/3016.
  </code></pre>