</div>
</div>
<div id="exercise-ggfx-dither" class="callout-body-container callout-body">
<p>A script containing this code is included as the <code>ggfx-dither.R</code> file</p>
</div>
</div>
</section>
<section id="mask" class="level2 page-columns page-full">
<h2 class="anchored" data-anchor-id="mask">Mask</h2>
<p>One of my favourite filtering tricks is to use <code>with_mask()</code> as a way of displaying one layer of the plot <em>only</em> when it overlaps with a second layer (referred to as the “mask