public int getNumYTiles() {
        return getMaxTileY() - getMinTileY() + 1;
    }
Returns the number of tiles along the tile grid in the vertical
direction.  getNumYTiles() is implemented in terms
of getMinTileY() and getMaxTileY() and so does not need to be
implemented by subclasses.
plugins/svg-plugin/batik-codec-fix/src/main/java/org/apache/batik/ext/awt/image/codec/util/SimpleRenderedImage.java