public Vector getSources() {
        return null;
    }
Converts a vertical tile index into the Y coordinate of its
upper left pixel.  This is a convenience method.  No attempt is made
to detect out-of-range indices.

@param ty the vertical index of a tile.
@return the Y coordinate of the tile's upper left pixel.
plugins/svg-plugin/batik-codec-fix/src/main/java/org/apache/batik/ext/awt/image/codec/util/SimpleRenderedImage.java