ETAILS ON THE GEOMETRY
</p><p>
As mentioned, the <a href="%pathto:vl_dsift;">VL_DSIFT</a>() descriptors cover the bounding box
specified by BOUNDS = [XMIN YMIN XMAX YMAX]. Thus the top-left bin
of the top-left descriptor is placed at (XMIN, YMIN). The next
three bins to the right are at XMIN + SIZE, XMIN + 2*SIZE, XMIN +
3*SIZE. The X coordiante of the center of the first descriptor is
therefore at (XMIN + XMIN + 3*SIZE) / 2 = XMIN + 3/2 * SIZE.  For
instance, if XMIN = 1 and SIZE = 3 (default values), the 