public class SplmageEventHandler extends ImageEventAdapter {

	private String columnName;
	
	@Override
	public void onPrepare(IImage imageHandle, IReportContext reportContext) throws ScriptException {
		columnName = StringUtils.substringBetween(StringUtils.substringBetween(imageHandle.getValueExpression(), "[", "]"), "\"", "\"");
	}
	
	@Override
	public void onCreate(IImageInstance image, IReportContext reportContext) throws ScriptException {
		final Object data = image.getRowData().getColumnValue(getColumnName());
		if (data != null) {
			...
			if (...) {
				image.setMimeType("image/svg+xml");
			}
		}
	}

	public String getColumnName() {
		return columnName;
	}

}