Add a region growing example

examples/region-growing.html

@@ -0,0 +1,43 @@
+---
+template: example.html
+title: Region Growing
+shortdesc: Grow a region from a seed pixel
+docs: >
+  <p>Click a region on the map. The computed region will be red.</p>
+  <p>
+    This example uses a <code>ol.source.Raster</code> to generate data
+    based on another source.  The raster source accepts any number of
+    input sources (tile or image based) and runs a pipeline of
+    operations on the input data.  The return from the final
+    operation is used as the data for the output source.
+  </p>
+  <p>
+    In this case, a single tiled source of imagery data is used as input.
+    The region is calculated in a single "image" operation using the "seed"
+    pixel provided by the user clicking on the map. The "threshold" value
+    determines whether a given contiguous pixel belongs to the "region" - the
+    difference between a candidate pixel's RGB values and the seed values must
+    be below the threshold.
+  </p>
+  <p>
+    This example also shows how an additional function can be made available
+    to the operation.
+  </p>
+tags: "raster, region growing"
+---
+<div class="row-fluid">
+  <div class="span12">
+    <div id="map" class="map"></div>
+  </div>
+</div>
+<div class="row">
+  <div class="col-md-1">
+    Threshold:
+  </div>
+  <div class="col-md-2">
+    <input id="threshold" type="range" min="1" max="50" value="20"/>
+  </div>
+  <div class="col-md-1">
+    <span id="threshold-value"></span>
+  </div>
+</div>