title: phpThumb is not setting parameter – fltr[] usm
body: <p>I am using Brett's <a href="http://mrphp.com.au/blog/image-cache-using-phpthumb-and-modrewrite" rel="nofollow">Mr. PHP thumb caching script</a> along with phpThumb to create my thumbs. It works extremely well, except for one thing... I cannot get it to set and process the UnSharpMask filter.  The relevant part of the script looks like this:</p>
  
  <pre><code>// generate the thumbnail
  require('../phpthumb/phpthumb.class.php');
  $phpThumb = new phpThumb();
  $phpThumb-&gt;setSourceFilename($image);
  $phpThumb-&gt;setParameter('w',$width);
  $phpThumb-&gt;setParameter('h',$height);
  $phpThumb-&gt;setParameter('q','95'); // set the quality to 95%
  $phpThumb-&gt;setParameter('fltr[]','usm|80|0.5|3'); // &lt;--- THIS SHOULD SET THE USM FILTER
  $phpThumb-&gt;setParameter('f',substr($thumb,-3,3)); // set the output file format
  
  if (!$phpThumb-&gt;GenerateThumbnail()) {
      error('cannot generate thumbnail');
  }
  </code></pre>
  
  <p>I'm guessing there's a problem with my syntax, since the fltr[] parameter requires brackets.  I have tried escaping the brackets like so: 'fltr[]' but that didn't work either.</p>
  
  <p>I've used several other possible parameters with good success (zoom cropping, max height, max width, etc...)  Everything seems to work except the filters (including usm - UnSharpMask).</p>
  
  <p>I don't get any errors.  It spits out thumbs all day long.  They're just not sharpened.</p>
  
  <p>For reference, here's the <a href="http://phpthumb.sourceforge.net/demo/docs/phpthumb.readme.txt" rel="nofollow">official phpThumb readme file</a> that discusses all the possible settings and filters.</p>
  
  <p>Thanks for looking.</p>