Fix image-filter example using right postrender events

examples/image-filter.html

@@ -3,9 +3,9 @@ layout: example.html
 title: Image Filters
 shortdesc: Apply a filter to imagery
 docs: >
-  <p>Layer rendering can be manipulated in <code>precompose</code> and <code>postcompose</code> event listeners.
+  <p>Layer rendering can be manipulated in <code>prerender</code> and <code>postrender</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>
+  In this example, the <code>postrender</code> listener applies a filter to the image data.</p>
 tags: "filter, image manipulation"
 cloak:
   - key: As1HiMj1PvLPlqc_gtM7AqZfBL8ZL3VrjaS3zIb22Uvb9WKhuJObROC-qUpa81U5

examples/image-filter.js

@@ -90,9 +90,9 @@ select.onchange = function() {
 
 
 /**
- * Apply a filter on "postcompose" events.
+ * Apply a filter on "postrender" events.
  */
-imagery.on('postcompose', function(event) {
+imagery.on('postrender', function(event) {
   convolve(event.context, selectedKernel);
 });