title: Codeigniter resizing image with fix width
body: <p>I'm trying to use Codeigniter's Image Manipulation Class to resize some images. I want to set the width to 150px and let the height change according with the new width. I.e. if I have a 300x200 image, it will become 150x100; if I have a 300x500 image, it will become 150x250.</p>
  
  <p>With this configuration, portrait images widht is less than 150px:</p>
  
  <pre><code>$config['maintain_ratio'] = TRUE;
  $config['width'] = 150;
  $config['height'] = 150;
  </code></pre>
  
  <p>If I don't set $config['height'] the resize class doesn't work as I hope.
  Is there a way to set a fix width and change height accordingly?</p>