+The Borders reflect how borders between regions are drawn. If
+@code{endian} is 1, then values inside Borders, including
+@code{endian} itself, are big-endian, otherwise they are
+little-endian. In practice, they seem to always be big-endian, even
+though the rest of the file is little-endian. @code{n-borders} seems
+to always be 19. @code{show-grid-lines} is 1 to draw grid lines,
+otherwise 0.
+
+Each Border describes one kind of border. Each @code{border-type}
+appears once in order, and they correspond to the following borders:
+
+@table @asis
+@item 0
+Title.
+@item 1@dots{}4
+Left, top, right, and bottom outer frame.
+@item 5@dots{}8
+Left, top, right, and bottom inner frame.
+@item 9, 10
+Left and top of data area.
+@item 11, 12
+Horizontal and vertical dimension rows.
+@item 13, 14
+Horizontal and vertical dimension columns.
+@item 15, 16
+Horizontal and vertical category rows.
+@item 17, 18
+Horizontal and vertical category columns.
+@end table
+
+@code{stroke-type} describes how a border is drawn, as one of:
+
+@table @asis
+@item 0
+No line.
+@item 1
+Solid line.
+@item 2
+Dashed line.
+@item 3
+Thick line.
+@item 4
+Thin line.
+@item 5
+Double line.
+@end table
+
+@code{color} is an RGB color. Bits 24--31 are alpha, bits 16--23 are
+red, 8--15 are green, 0--7 are blue. An alpha of 255 indicates an
+opaque color, therefore opaque black is 0xff000000.