tt>: x coordinate</p><p><tt>y</tt>: y coordinate</p><pre class="codeinput">        <span class="keyword">function</span> unpaint(obj, x, y)
            img = obj.getCData();
            img(y, x) = 0;
            obj.setCData(img);
            obj.setAlphaData(img);
        <span class="keyword">end</span>
</pre><h2>undoLastPoint<a name="15"></a></h2><p>Unpaints and removes the newest click in the stack</p><pre class="codeinput">        <span class="keyword">function</span> undoLastPoint(obj)
            x 