Contour Color Scale

This example demonstrates using various color scales for contour charts.

ChartDirector supports two ways to configure the color scale:

The ColorAxis.setColorGradient can be used to specify a list of colors to be used for the ColorAxis. With this method, the color scale is determined by other means, and the colors will be applied to the resulting scale, interpolating among the colors if necessary. By default, the color axis scale and labels are automatically determined based on actual data. The axis scale and labels can also be specified by using various Axis methods, such as Axis.setLinearScale, Axis.setLogScale and Axis.setDateScale (please refer to Axis for the full list).
The ColorAxis.setColorScale can be used to specify both the colors and the associated scale and labels.

This example includes 4 charts to demonstrate both of the above methods.

The following is the command line version of the code in "cppdemo/contourcolor". The MFC version of the code is in "mfcdemo/mfcdemo". The Qt Widgets version of the code is in "qtdemo/qtdemo". The QML/Qt Quick version of the code is in "qmldemo/qmldemo".

#include "chartdir.h"

void createChart(int chartIndex, const char *filename)
{
    // The x and y coordinates of the grid
    double dataX[] = {-4, -3, -2, -1, 0, 1, 2, 3, 4};
    const int dataX_size = (int)(sizeof(dataX)/sizeof(*dataX));
    double dataY[] = {-4, -3, -2, -1, 0, 1, 2, 3, 4};
    const int dataY_size = (int)(sizeof(dataY)/sizeof(*dataY));

    // Use random numbers for the z values on the XY grid
    RanSeries* r = new RanSeries(99);
    DoubleArray dataZ = r->get2DSeries(dataX_size, dataY_size, -0.9, 0.9);

    // Create a XYChart object of size 420 x 360 pixels
    XYChart* c = new XYChart(420, 360);

    // Set the plotarea at (30, 25) and of size 300 x 300 pixels. Use semi-transparent grey
    // (0xdd000000) horizontal and vertical grid lines
    c->setPlotArea(30, 25, 300, 300, -1, -1, -1, 0xdd000000, -1);

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

    // Add a contour layer using the given data
    ContourLayer* layer = c->addContourLayer(DoubleArray(dataX, dataX_size), DoubleArray(dataY,
        dataY_size), dataZ);

    // Enable contour label by setting its style to black (000000) 8pt default bold font
    layer->setContourLabelStyle("bold", 8, 0x000000);

    // Set the label to display the value in a CDML block with semi-transparent white (4FFFFFFF)
    // background and 2 pixels left/right margin and 1 pixel top/bottom margin
    layer->setContourLabelFormat("<*block,bgcolor=4FFFFFFF,margin=2 2 1 1*>{value}");

    // Move the grid lines in front of the contour layer
    c->getPlotArea()->moveGridBefore(layer);

    // Add a color axis (the legend) in which the top left corner is anchored at (350, 25). Set the
    // length to 400 300 and the labels on the right side.
    ColorAxis* cAxis = layer->setColorAxis(350, 25, Chart::TopLeft, 300, Chart::Right);

    if (chartIndex == 1) {
        // Speicify a color gradient as a list of colors, and use it in the color axis.
        int colorGradient[] = {0x0044cc, 0xffffff, 0x00aa00};
        const int colorGradient_size = (int)(sizeof(colorGradient)/sizeof(*colorGradient));
        cAxis->setColorGradient(false, IntArray(colorGradient, colorGradient_size));
    } else if (chartIndex == 2) {
        // Specify the color scale to use in the color axis
        double colorScale[] = {-1.0, 0x1a9850, -0.75, 0x66bd63, -0.5, 0xa6d96a, -0.25, 0xd9ef8b, 0,
            0xfee08b, 0.25, 0xfdae61, 0.5, 0xf46d43, 0.75, 0xd73027, 1};
        const int colorScale_size = (int)(sizeof(colorScale)/sizeof(*colorScale));
        cAxis->setColorScale(DoubleArray(colorScale, colorScale_size));
    } else if (chartIndex == 3) {
        // Specify the color scale to use in the color axis. Also specify an underflow color
        // 0x66ccff (blue) for regions that fall below the lower axis limit.
        double colorScale[] = {0, 0xffff99, 0.2, 0x80cdc1, 0.4, 0x35978f, 0.6, 0x01665e, 0.8,
            0x003c30, 1};
        const int colorScale_size = (int)(sizeof(colorScale)/sizeof(*colorScale));
        cAxis->setColorScale(DoubleArray(colorScale, colorScale_size), 0x66ccff);
    }

    // Output the chart
    c->makeChart(filename);

    //free up resources
    delete r;
    delete c;

}

int main(int argc, char *argv[])
{
    createChart(0, "contourcolor0.png");
    createChart(1, "contourcolor1.png");
    createChart(2, "contourcolor2.png");
    createChart(3, "contourcolor3.png");
    return 0;
}