Decorating a JFreeChart

Question

I would like to decorate all my generated JFreeCharts with a timestamp in the corner. Is there a way within the JFreeChart framework to draw on the image after the chart has been generated?

EDIT: Note that these charts are being generated in a background thread and distributed via a servlet, so there is no GUI and I can't just display the timestamp on a separate component.

Answer 1

One approach would be to subclass ChartPanel and override the paint(Graphics) method to first chain to super.paint(Graphics) and subsequently render the additional text on top of the chart.

This feels a bit hacky to me though and I'd personally favour simply adding the ChartPanel to another container JPanel along with a JLabel representing the timestamp.

Answer 2

After dinking around with it some more, I found a solution that lets you draw arbitrarily on the image after JFreeChart is done with it, so I'll post it here for posterity. In my case, I was writing the chart to an OutputStream, so my code looked something like this:

BufferedImage chartImage = chart.createBufferedImage(width, height, null);
Graphics2D g = (Graphics2D) chartImage.getGraphics();
/* arbitrary drawing happens here */
EncoderUtil.writeBufferedImage(chartImage, ImageFormat.PNG, outputStream);