How to export GRAL plot to JPG?

I'm trying to export example GRAL Pie plot to jpg using:

private byte[] getJpg() throws IOException {
    BufferedImage bImage = new BufferedImage(800, 600, BufferedImage.TYPE_INT_RGB);
    Graphics2D g2d = bImage.createGraphics();
    DrawingContext drawingContext = new DrawingContext(g2d, DrawingContext.Quality.QUALITY,
            DrawingContext.Target.BITMAP);
    PiePlot plot = getPlot();
    plot.draw(drawingContext);

    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    ImageIO.write(bImage, "jpg", baos);
    baos.flush();
    byte[] bytes = baos.toByteArray();
    baos.close();
    return bytes;
}

But it renders as black rectangle with some legend information (legend is ok). Who knows the right way to render JPG from GRAL plot?