+ /**
+ * Build a masking image of hidden columns and rows to be applied on top of
+ * the main overview image.
+ *
+ * @param rows
+ * collection of rows the overview is built over
+ * @param cols
+ * collection of columns the overview is built over
+ * @param width
+ * width of overview in pixels
+ * @param height
+ * height of overview in pixels
+ * @return BufferedImage containing mask of hidden regions
+ */
+ private BufferedImage buildHiddenImage(AlignmentRowsCollectionI rows,
+ AlignmentColsCollectionI cols, int width, int height)