ChartDirector 6.0 (Ruby 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

[Ruby On Rails Version - Controller] app/controllers/contourinterpolate_controller.rb
require("chartdirector")

class ContourinterpolateController < ApplicationController

    def index()
        @title = "Contour Interpolation"
        @ctrl_file = File.expand_path(__FILE__)
        @noOfCharts = 4
        render :template => "templates/chartview"
    end

    #
    # Render and deliver the chart
    #
    def getchart()
        # This script can draw different charts depending on the chartIndex
        chartIndex = (params["img"]).to_i

        # The x and y coordinates of the grid
        dataX = [-4, -3, -2, -1, 0, 1, 2, 3, 4]
        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).
        dataZ = Array.new(dataX.length * dataY.length, 0)
        0.upto(dataY.length - 1) do |yIndex|
            y = dataY[yIndex]
            0.upto(dataX.length - 1) do |xIndex|
                x = dataX[xIndex]
                dataZ[yIndex * dataX.length + xIndex] = Math.sin(x * 3.1416 / 3) * Math.sin(
                    y * 3.1416 / 3)
            end
        end

        # Create a XYChart object of size 360 x 360 pixels
        c = ChartDirector::XYChart.new(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
        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", "arialbi.ttf", 12)
        elsif chartIndex == 1
            # Discrete coloring, linear surface interpolation
            c.addTitle("Linear Surface - Discrete Coloring", "arialbi.ttf", 12)
            layer.setSmoothInterpolation(false)
        elsif chartIndex == 2
            # Smooth coloring, spline surface interpolation
            c.addTitle("Spline Surface - Continuous Coloring", "arialbi.ttf", 12)
            layer.setContourColor(ChartDirector::Transparent)
            layer.colorAxis().setColorGradient(true)
        else
            # Discrete coloring, linear surface interpolation
            c.addTitle("Linear Surface - Continuous Coloring", "arialbi.ttf", 12)
            layer.setSmoothInterpolation(false)
            layer.setContourColor(ChartDirector::Transparent)
            layer.colorAxis().setColorGradient(true)
        end

        # Output the chart
        send_data(c.makeChart2(ChartDirector::JPG), :type => "image/jpeg", :disposition => "inline")

    end

end

[Ruby On Rails Version - View] app/views/templates/chartview.html.erb
<html>
<body style="margin:5px 0px 0px 5px">

<!-- Title -->
<div style="font-size:18pt; font-family:verdana; font-weight:bold">
    <%= @title %>
</div>
<hr style="border:solid 1px #000080" />

<!-- Source Code Listing Link -->
<div style="font-size:9pt; font-family:verdana; margin-bottom:1.5em">
    <%= link_to "Source Code Listing", 
        :controller => "cddemo", :action => "viewsource",
        :ctrl_file => @ctrl_file, :view_file => File.expand_path(__FILE__) %>
</div>

<!-- Create one or more IMG tags to display the demo chart(s) -->
<% 0.upto(@noOfCharts - 1) do |i| %>
    <img src="<%= url_for(:action => "getchart", :img => i) %>">
<% end %>

</body>
</html>

[Command Line Version] rubydemo/contourinterpolate.rb
#!/usr/bin/env ruby
require("chartdirector")

def createChart(chartIndex)

    # The x and y coordinates of the grid
    dataX = [-4, -3, -2, -1, 0, 1, 2, 3, 4]
    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).
    dataZ = Array.new(dataX.length * dataY.length, 0)
    0.upto(dataY.length - 1) do |yIndex|
        y = dataY[yIndex]
        0.upto(dataX.length - 1) do |xIndex|
            x = dataX[xIndex]
            dataZ[yIndex * dataX.length + xIndex] = Math.sin(x * 3.1416 / 3) * Math.sin(
                y * 3.1416 / 3)
        end
    end

    # Create a XYChart object of size 360 x 360 pixels
    c = ChartDirector::XYChart.new(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
    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", "arialbi.ttf", 12)
    elsif chartIndex == 1
        # Discrete coloring, linear surface interpolation
        c.addTitle("Linear Surface - Discrete Coloring", "arialbi.ttf", 12)
        layer.setSmoothInterpolation(false)
    elsif chartIndex == 2
        # Smooth coloring, spline surface interpolation
        c.addTitle("Spline Surface - Continuous Coloring", "arialbi.ttf", 12)
        layer.setContourColor(ChartDirector::Transparent)
        layer.colorAxis().setColorGradient(true)
    else
        # Discrete coloring, linear surface interpolation
        c.addTitle("Linear Surface - Continuous Coloring", "arialbi.ttf", 12)
        layer.setSmoothInterpolation(false)
        layer.setContourColor(ChartDirector::Transparent)
        layer.colorAxis().setColorGradient(true)
    end

    # Output the chart
    c.makeChart("contourinterpolate%s.jpg" % chartIndex)
end

createChart(0)
createChart(1)
createChart(2)
createChart(3)