ntly (e.g. in filters).</p>
<p>The <code class="docutils literal"><span class="pre">virtual_2d_locator</span></code> is a locator that is instantiated with a function
object invoked upon dereferencing a pixel. It returns the value of a pixel
given its X,Y coordinates. Virtual locators can be used to implement virtual
image views that can model any user-defined function. See the GIL tutorial for
an example of using virtual locators to create a view of the Mandelbrot set.</p>
<p>Both the virtual and the memor