---
template: "example.html"
title: "Image Filter Example"
shortdesc: "Apply a filter to imagery"
docs: >
  <p>Layer rendering can be manipulated in <code>precompose</code> and <code>postcompose</code> event listeners.
  These listeners get an event with a reference to the Canvas rendering context.
  In this example, the <code>postcompose</code> listener applies a filter to the image data.</p>
tags: "filter, image manipulation"
---
<div class="row-fluid">
  <div class="span12">
    <div id="map" class="map"></div>
  </div>
</div>
<select id="kernel" name="kernel">
  <option>none</option>
  <option selected>sharpen</option>
  <option value="sharpenless">sharpen less</option>
  <option>blur</option>
  <option>shadow</option>
  <option>emboss</option>
  <option value="edge">edge detect</option>
</select>