title: Commands for ImageMagick to create thumbnails
body: <p>Given an photograph uploaded by a user, what is best approach to creating a number various sized thumbnails Using ImageMagick (or GraphicsMagick)? My guess to the steps:</p>
  
  <ol>
  <li>Create a super sample of the image, maintaining original aspect ratio</li>
  <li>Apply watermark to super sample</li>
  <li>Create the various sized thumbnails using the watermarked super sampled image</li>
  </ol>
  
  <p>Additional requirements:</p>
  
  <ol>
  <li>Best quality possible (does this mean PNG over JPG?)</li>
  <li>Smallest file size possible (does this mean JPG over PNG?)</li>
  <li>Use density of 72x72, units is ppi</li>
  </ol>
  
  <p>Since I am not that familiar with the intricacies of IM (or GM), some guidance to the best commands that meet my objectives would be highly appreciated. Thanks.</p>