I want to draw a circle on a x-y graph using RTGenshape. the circle should always be centered at a specific (x,y) location in the graph, say (-10,20) even as the xaxis min,max and yaxis min-max change. (We can assume that (-10,20) is always within the current plot area). In addition, the circle should always be of a fixed diameter specified in device coordinates say, always 3 mm (or always 10 pixels), regardless of the plot scaling.
It's easiest to use the ChartSymbol class, which already has a CIRCLE type defined. The SymbolSize is specified in pixels, the location in the current plot scale.
ChartAttribute attrib4 = new ChartAttribute(Color.Red, 1, DashStyle.Solid);
attrib4.SymbolSize = 64;
ChartSymbol circle = new ChartSymbol(pTransform1, ChartObj.CIRCLE, attrib4);
circle.SetLocation(-10, 20);
chartVu.AddChartObject(circle);
This may not solve my problem. If I understand it correctly, the chart symbol SetLocation refers to the top,left corner of the enclosing rectangle. If I want the circle to be CENTERED at -10,20, and I want the circle to be say 12 pixels radius, then I want the top left corner at
x = -10 - (12 * plotUnits/pixel) y = 20 - (12 * plotUnits/pixel)
How do I get transform 1 plot unit to equivalent pixel units?
You are creating problem where they don't exist. The ChartSymbol symbols are centered on the specified location. Run the code fragment we posted and you will see this.
Need help on coordinate transformation
Posted - 17 Nov 2008 : 19:28:23
