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.

[File: phpdemo/contourinterpolate.php]

<?php
require_once("../lib/phpchartdir.php");

function createChart($viewer, $chartIndex)
{
    # The x and y coordinates of the grid
    $dataX = array(-4, -3, -2, -1, 0, 1, 2, 3, 4);
    $dataY = array(-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).
    $dataZ = array_fill(0, count($dataX) * count($dataY), 0);
    for($yIndex = 0; $yIndex < count($dataY); ++$yIndex) {
        $y = $dataY[$yIndex];
        for($xIndex = 0; $xIndex < count($dataX); ++$xIndex) {
            $x = $dataX[$xIndex];
            $dataZ[$yIndex * count($dataX) + $xIndex] = sin($x * 3.1416 / 3) * sin($y * 3.1416 / 3);
        }
    }

    # Create a XYChart object of size 360 x 360 pixels
    $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
    $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(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(Transparent);
        $layer->colorAxis->setColorGradient(true);
    }

    # Output the chart
    $viewer->setChart($c, SVG);
}

# This example includes 4 charts
$viewers = array();
for ($i = 0; $i < 4; ++$i) {
    $viewers[$i] = new WebChartViewer("chart$i");
    createChart($viewers[$i], $i);
}
?>

<!DOCTYPE html>
<html>
<head>
    <title>Contour Interpolation</title>
    <!-- Include ChartDirector Javascript Library to support chart interactions -->
    <script type="text/javascript" src="cdjcv.js"></script>
</head>
<body style="margin:5px 0px 0px 5px">
    <div style="font:bold 18pt verdana;">
        Contour Interpolation
    </div>
    <hr style="border:solid 1px #000080; background:#000080" />
    <div style="font:10pt verdana; margin-bottom:1.5em">
        <a href="viewsource.php?file=<?=basename(__FILE__)?>">View Chart Source Code</a>
    </div>
    <!-- ****** Here are the chart images ****** -->
    <?php
        for ($i = 0; $i < count($viewers); ++$i) {
            echo $viewers[$i]->renderHTML(), " ";
        }
    ?>
</body>
</html>