title: PHP/GD Gaussian Blur Effect
body: <p>I need to obfuscate a certain area of an image using PHP and GD, currently I'm using the following code:</p>
  
  <pre><code>for ($x = $_GET['x1']; $x &lt; $_GET['x2']; $x += $pixel)
  {
      for ($y = $_GET['y1']; $y &lt; $_GET['y2']; $y += $pixel)
      {
          ImageFilledRectangle($image, $x, $y, $x + $pixel - 1, $y + $pixel - 1, ImageColorAt($image, $x, $y));
      }
  }
  </code></pre>
  
  <p>This basically replaces the selected area with squares of $pixel pixels. I want to accomplish some kind of blur (gaussian preferably) effect, I know I can use the ImageFilter() function:</p>
  
  <pre><code>ImageFilter($image, IMG_FILTER_GAUSSIAN_BLUR);
  </code></pre>
  
  <p>But it blurs the entire canvas, my problem is that I just want to blur a specific area.</p>