title: how can i change the dpi of an image with the imagick extension
body: <p>I need to change all uploaded files to 72 dpi.
  I'm using the php imagick extension.</p>
  
  <p>heres what i've tried (the image i'm using is 300dpi):</p>
  
  <pre><code>$image = new Imagick();
  $image-&gt;setResolution(72,72) ;
  $image-&gt;readImage($img);
  $image-&gt;resampleImage  (72,72,imagick::FILTER_UNDEFINED,1);
  $image-&gt;writeImage($target)
  </code></pre>
  
  <p>this doesn't seem to anything.
  the image is uploading, but stays at 300dpi</p>