ImageGraph of unique visitors per day in custom date range

I’m trying to generate a static PNG using the ImageGraph API but I’m stuck.

What I want is the same graph as in the default “Visits over time” widget, only static and with unique visitors.

Here’s the widget configured as I want it to look:

http://demo.piwik.org/index.php?module=Widgetize&action=iframe&columns[]=nb_uniq_visitors&moduleToWidgetize=VisitsSummary&actionToWidgetize=getEvolutionGraph&idSite=7&period=range&date=2012-11-03,2012-11-06&disableLink=1&widget=1

I tried using the same parameters (values) in an ImageGraph API call but I always get an “Invalid API Module and/or Action” error. Here’s the url I tried:

http://demo.piwik.org/?module=API&method=ImageGraph.get&idSite=7&period=range&date=2012-11-03,2012-11-06&apiModule=VisitsSummary&apiAction=getEvolutionGraph&outputType=0&showLegend=1&fontSize=9&aliasedGraph=1&legendAppendMetric=1&format=xml&token_auth=anonymous&columns[]=nb_uniq_visitors

Can anyone tell me what I did wrong or if it’s even possible?
I’d also like, if possible, to integrate a graph of conversions for 1 (or more) specific goals.

Thanks
Thomas