ChartDirector 6.1 (Java Edition)

Contour Interpolation


      

This example demonstrates spline and linear surface interpolation, and discrete and continuous coloring for the ContourLayer.

The input to the contour layer are the z values at certain (x, y) points. To draw the contour and to color the layer, it is necessarily to know the z values at all pixels in the xy plane. ChartDirector uses surface interpolation to compute the z values at all pixels from the given data points. Two types of interpolation - spline and linear - are supported. They can be configured using ContourLayer.setSmoothInterpolation.

The coloring of the contour layer can be discrete or continuous, configurable using ColorAxis.setColorGradient or ColorAxis.setColorScale.

Source Code Listing

[JSP Version] jspdemo/contourinterpolate.jsp
<%@page import="ChartDirector.*" %>
<%@page import="javax.servlet.http.*" %>
<%!
// A simple structure to represent a chart image with an image map
private static class ImageWithHotSpot
{
    String imageURL;
    String imageMap;
}

// Function to create the demo charts
ImageWithHotSpot createChart(HttpServletRequest request, int chartIndex)
{
    // The x and y coordinates of the grid
    double[] dataX = {-4, -3, -2, -1, 0, 1, 2, 3, 4};
    double[] dataY = {-4, -3, -2, -1, 0, 1, 2, 3, 4};

    // The values at the grid points. In this example, we will compute the values using the formula
    // z = Sin(x * pi / 3) * Sin(y * pi / 3).
    double[] dataZ = new double[dataX.length * dataY.length];
    for (int yIndex = 0; yIndex < dataY.length; ++yIndex) {
        double y = dataY[yIndex];
        for (int xIndex = 0; xIndex < dataX.length; ++xIndex) {
            double x = dataX[xIndex];
            dataZ[yIndex * dataX.length + xIndex] = Math.sin(x * 3.1416 / 3) * Math.sin(y * 3.1416 /
                3);
        }
    }

    // Create a XYChart object of size 360 x 360 pixels
    XYChart c = new XYChart(360, 360);

    // Set the plotarea at (30, 25) and of size 300 x 300 pixels. Use semi-transparent black
    // (c0000000) for both horizontal and vertical grid lines
    c.setPlotArea(30, 25, 300, 300, -1, -1, -1, 0xc0000000, -1);

    // Add a contour layer using the given data
    ContourLayer layer = c.addContourLayer(dataX, dataY, dataZ);

    // Set the x-axis and y-axis scale
    c.xAxis().setLinearScale(-4, 4, 1);
    c.yAxis().setLinearScale(-4, 4, 1);

    if (chartIndex == 0) {
        // Discrete coloring, spline surface interpolation
        c.addTitle("Spline Surface - Discrete Coloring", "Arial Bold Italic", 12);
    } else if (chartIndex == 1) {
        // Discrete coloring, linear surface interpolation
        c.addTitle("Linear Surface - Discrete Coloring", "Arial Bold Italic", 12);
        layer.setSmoothInterpolation(false);
    } else if (chartIndex == 2) {
        // Smooth coloring, spline surface interpolation
        c.addTitle("Spline Surface - Continuous Coloring", "Arial Bold Italic", 12);
        layer.setContourColor(Chart.Transparent);
        layer.colorAxis().setColorGradient(true);
    } else {
        // Discrete coloring, linear surface interpolation
        c.addTitle("Linear Surface - Continuous Coloring", "Arial Bold Italic", 12);
        layer.setSmoothInterpolation(false);
        layer.setContourColor(Chart.Transparent);
        layer.colorAxis().setColorGradient(true);
    }

    // Output the chart
    ImageWithHotSpot ret = new ImageWithHotSpot();
    ret.imageURL = c.makeSession(request, "chart" + chartIndex, Chart.JPG);
    return ret;
}
%>
<%
ImageWithHotSpot chart0 = createChart(request, 0);
ImageWithHotSpot chart1 = createChart(request, 1);
ImageWithHotSpot chart2 = createChart(request, 2);
ImageWithHotSpot chart3 = createChart(request, 3);
%>
<html>
<body style="margin:5px 0px 0px 5px">
<div style="font-size:18pt; font-family:verdana; font-weight:bold">
    Contour Interpolation
</div>
<hr color="#000080">
<div style="font-size:10pt; font-family:verdana; margin-bottom:1.5em">
    <a href="viewsource.jsp?file=<%=request.getServletPath()%>">View Source Code</a>
</div>
<img src='<%=response.encodeURL("getchart.jsp?"+chart0.imageURL)%>'>
<img src='<%=response.encodeURL("getchart.jsp?"+chart1.imageURL)%>'>
<img src='<%=response.encodeURL("getchart.jsp?"+chart2.imageURL)%>'>
<img src='<%=response.encodeURL("getchart.jsp?"+chart3.imageURL)%>'>
</body>
</html>

[Java Version] javademo/contourinterpolate.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import ChartDirector.*;

public class contourinterpolate implements DemoModule
{
    //Name of demo program
    public String toString() { return "Contour Interpolation"; }

    //Number of charts produced in this demo
    public int getNoOfCharts() { return 4; }

    //Main code for creating charts
    public void createChart(ChartViewer viewer, int chartIndex)
    {
        // The x and y coordinates of the grid
        double[] dataX = {-4, -3, -2, -1, 0, 1, 2, 3, 4};
        double[] dataY = {-4, -3, -2, -1, 0, 1, 2, 3, 4};

        // The values at the grid points. In this example, we will compute the values using the
        // formula z = Sin(x * pi / 3) * Sin(y * pi / 3).
        double[] dataZ = new double[dataX.length * dataY.length];
        for (int yIndex = 0; yIndex < dataY.length; ++yIndex) {
            double y = dataY[yIndex];
            for (int xIndex = 0; xIndex < dataX.length; ++xIndex) {
                double x = dataX[xIndex];
                dataZ[yIndex * dataX.length + xIndex] = Math.sin(x * 3.1416 / 3) * Math.sin(y *
                    3.1416 / 3);
            }
        }

        // Create a XYChart object of size 360 x 360 pixels
        XYChart c = new XYChart(360, 360);

        // Set the plotarea at (30, 25) and of size 300 x 300 pixels. Use semi-transparent black
        // (c0000000) for both horizontal and vertical grid lines
        c.setPlotArea(30, 25, 300, 300, -1, -1, -1, 0xc0000000, -1);

        // Add a contour layer using the given data
        ContourLayer layer = c.addContourLayer(dataX, dataY, dataZ);

        // Set the x-axis and y-axis scale
        c.xAxis().setLinearScale(-4, 4, 1);
        c.yAxis().setLinearScale(-4, 4, 1);

        if (chartIndex == 0) {
            // Discrete coloring, spline surface interpolation
            c.addTitle("Spline Surface - Discrete Coloring", "Arial Bold Italic", 12);
        } else if (chartIndex == 1) {
            // Discrete coloring, linear surface interpolation
            c.addTitle("Linear Surface - Discrete Coloring", "Arial Bold Italic", 12);
            layer.setSmoothInterpolation(false);
        } else if (chartIndex == 2) {
            // Smooth coloring, spline surface interpolation
            c.addTitle("Spline Surface - Continuous Coloring", "Arial Bold Italic", 12);
            layer.setContourColor(Chart.Transparent);
            layer.colorAxis().setColorGradient(true);
        } else {
            // Discrete coloring, linear surface interpolation
            c.addTitle("Linear Surface - Continuous Coloring", "Arial Bold Italic", 12);
            layer.setSmoothInterpolation(false);
            layer.setContourColor(Chart.Transparent);
            layer.colorAxis().setColorGradient(true);
        }

        // Output the chart
        viewer.setChart(c);
    }

    //Allow this module to run as standalone program for easy testing
    public static void main(String[] args)
    {
        //Instantiate an instance of this demo module
        DemoModule demo = new contourinterpolate();

        //Create and set up the main window
        JFrame frame = new JFrame(demo.toString());
        frame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {System.exit(0);} });
        frame.getContentPane().setBackground(Color.white);
        frame.getContentPane().setLayout(new FlowLayout(FlowLayout.LEFT));
        frame.setSize(800, 450);

        // Create the charts and put them in the content pane
        for (int i = 0; i < demo.getNoOfCharts(); ++i)
        {
            ChartViewer viewer = new ChartViewer();
            demo.createChart(viewer, i);
            frame.getContentPane().add(viewer);
        }

        // Display the window
        frame.setVisible(true);
    }
}