+// Single images in the Internet Archive scandata.xml metadata are (somewhat incorrectly)
+// given a "leaf" number. Some of these images from the scanning process should not
+// be displayed in the BookReader (for example colour calibration cards). Since some
+// of the scanned images will not be displayed in the BookReader (those marked with
+// addToAccessFormats false in the scandata.xml) leaf numbers and BookReader page
+// indexes are generally not the same. This function returns the BookReader page
+// index given a scanned leaf number.
+//
+// This function is used, for example, to map between search results (that use the
+// leaf numbers) and the displayed pages in the BookReader.