ContentEmitter question

tradiate

For some reports, like the one attached, there is only a chart, and no table data. I am trying to write a JSON emitter that can be run against any report, and render JSON that represents the data used to create the report. For reports that consist of only a chart, my emitter doesn't seem to get called for the various startXXX methods in the IContentEmitter interface. If I run my emitter against reports like, say, the classicModels.rptdesign, then I do get called (since the classicModels.rptdesign has table data).

What I'd like to do for these "chart-only" reports is somehow drill into them to get the raw data that was used to populate the chart.

Does anyone know how I should go about doing this? Are there existing emitters out there that I can use as a guide?