[C#]	public double getZAtPixel(int x, int y);
[VB]	Public Function getZAtPixel(x As Integer, y As Integer) As Double

Gets the z value at the specify (x, y) pixel coordinate.

Note: This method should be used only after ChartDirector has output the chart image, or after BaseChart.layout has been called.

The z value at the sepcified (x, y) pixel coordinate, or NoValue if the point lie outside the contour region.