to the
pixel location plus one integer for the row size in bytes, for a total of
8 bytes. <code class="docutils literal"><span class="pre">++loc.x()</span></code> amounts to incrementing a raw pointer (or N pointers
for planar images). Computing 2D offsets is slower as it requires
multiplication and addition. Filters, for example, need to access the same
neighbors for every pixel in the image, in which case the relative positions
can be cached into a raw byte difference using <code class="docutils literal">