Y Zone Coloring

This example demonstrates using y zone colors - colors that change at certain y value thresholds.

In this example, a y zone color is used as the fill color of an area layer, so that the area fill color changes above a certain threshold.

Y zone colors are created using Layer.yZoneColor. You can use a y zone color in any ChartDirector API that expects a color. For instance, you can use a y zone color as background color, fill color of data sets, line color, etc.

A single y zone color can support one threshold value and change between two colors. The two colors can be any colors, including another y zone color. You may create y zone colors with multiple thresholds by cascading multiple y zone colors this way.

The following is the command line version of the code in "cppdemo/yzonecolor". 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"

int main(int argc, char *argv[])
{
    // The data for the chart
    double data[] = {30, 28, 40, 55, 75, 68, 54, 60, 50, 62, 75, 65, 75, 89, 60, 55, 53, 35, 50, 66,
        56, 48, 52, 65, 62};
    const int data_size = (int)(sizeof(data)/sizeof(*data));

    // The labels for the chart
    const char* labels[] = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12",
        "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24"};
    const int labels_size = (int)(sizeof(labels)/sizeof(*labels));

    // Create a XYChart object of size 500 x 300 pixels, with a pale yellow (0xffffc0) background, a
    // black border, and 1 pixel 3D border effect
    XYChart* c = new XYChart(500, 300, 0xffffc0, 0x000000, 1);

    // Set the plotarea at (55, 50) and of size 420 x 205 pixels, with white background. Turn on
    // both horizontal and vertical grid lines with light grey color (0xc0c0c0)
    c->setPlotArea(55, 50, 420, 205, 0xffffff)->setGridColor(0xc0c0c0, 0xc0c0c0);

    // Add a legend box at (55, 25) (top of the chart) with horizontal layout. Use 8pt Arial font.
    // Set the background and border color to Transparent.
    LegendBox* legendBox = c->addLegend(55, 25, false, "", 8);
    legendBox->setBackground(Chart::Transparent);

    // Add keys to the legend box to explain the color zones
    legendBox->addKey("Normal Zone", 0x8033ff33);
    legendBox->addKey("Alert Zone", 0x80ff3333);

    // Add a title box to the chart using 13pt Arial Bold Italic font. The title is in CDML and
    // includes embedded images for highlight. The text is white (0xffffff) on a black background,
    // with a 1 pixel 3D border.
    c->addTitle(
        "<*block,valign=absmiddle*><*img=star.png*><*img=star.png*> Y Zone Color Demo "
        "<*img=star.png*><*img=star.png*><*/*>", "Arial Bold Italic", 13, 0xffffff)->setBackground(
        0x000000, -1, 1);

    // Add a title to the y axis
    c->yAxis()->setTitle("Energy Concentration (KJ per liter)");

    // Set the labels on the x axis.
    c->xAxis()->setLabels(StringArray(labels, labels_size));

    // Display 1 out of 3 labels on the x-axis.
    c->xAxis()->setLabelStep(3);

    // Add a title to the x axis using CDML
    c->xAxis()->setTitle("<*block,valign=absmiddle*><*img=clock.png*>  Elapsed Time (hour)<*/*>");

    // Set the axes width to 2 pixels
    c->xAxis()->setWidth(2);
    c->yAxis()->setWidth(2);

    // Add an area layer to the chart. The area is using a y zone color, where the color is
    // semi-transparent green below 60, and semi-transparent red above 60.
    c->addAreaLayer(DoubleArray(data, data_size), c->yZoneColor(60, 0x8033ff33, 0x80ff3333));

    // Add a custom CDML text at the bottom right of the plot area as the logo
    c->addText(475, 255,
        "<*block,valign=absmiddle*><*img=small_molecule.png*> <*block*><*font=Times New Roman Bold "
        "Italic,size=10,color=804040*>Molecular\nEngineering<*/*>")->setAlignment(Chart::BottomRight
        );

    // Output the chart
    c->makeChart("yzonecolor.png");

    //free up resources
    delete c;

    return 0;
}