- * will depend on feature location, visibility, ordering, and whether or not
- * transparency is applied. For feature rendering with transparency, this
- * class provides a dummy 'offscreen' graphics context where multiple feature
- * colours can be overlaid and the combined colour read back.
+ * will depend on feature location, visibility, ordering, colour scheme, and
+ * whether or not transparency is applied. For feature rendering with
+ * transparency, this class provides a dummy 'offscreen' graphics context
+ * where multiple feature colours can be overlaid and the combined colour read
+ * back.
+ * <p>
+ * This method is not thread-safe when transparency is applied, since a shared
+ * BufferedImage would be used by all threads to hold the composite colour at
+ * a position. Each thread should use a separate instance of this class.