MetatileMapOutputFormat may throw a
java.lang.ClassCastException: java.awt.image.Raster cannot be cast to java.awt.image.WritableRaster
when dealing with PlanarImage.
There is a piece of code getting a translatedChild from the PlanarImage metaTile, which is cast to WritableRaster. An exception occurs in case the returned Child is not a WritableRaster but simply Raster instead.