QwtPlot之绘制统计图

悠悠 2022-06-09 14:52 665阅读 0赞

QwtPlot是用来绘制二维图像的widget。在它的画板上可以无限制的显示绘画组件。绘画组件可以是曲线（QwtPlotCurve）、标记（QwtPlotMarker）、网格（QwtPlotGrid）、或者其它从QwtPlotItem继承的组件。

QwtScaleDraw可以用来绘制线性或对数尺度。一个标尺可以指定位置、对齐方式、长度等。标签可使用setLabelRotation()和setLabelAlignment()来设置旋转和对齐方式。通过QwtAbstractScaleDraw::setScaleDiv(const QwtScaleDiv &s)设置独立的标尺QwtScaleDiv对象， 标尺可以使用QwtAbstractScaleDraw::draw()函数来绘制。

看了一下QWT中关于distrowatch的代码，将其修改为天龙八部中十大高手排行榜，并添加了一些注释，排名是否正确先不做讨论，重在代码，^\_^便于理解！

//barchar.h
    
    #ifndef BAR_CHART_H
    #define BAR_CHART_H
    
    #include 
    
    class DistroChartItem;
    
    class BarChart: public QwtPlot
    {
        Q_OBJECT
    
    public:
        BarChart(QWidget *parent = NULL);
    
    public slots:
        void setOrientation(int value);
        void exportChart();
    
    private:
        void populate();
    
    private:
        DistroChartItem *d_barChartItem;
        QStringList d_distros;
    };
    
    #endif //BAR_CHART_H

//barchar.cpp
    
    #include "barchart.h"
    #include 
    #include 
    #include 
    #include 
    #include 
    #include 
    #include 
    
    class DistroScaleDraw: public QwtScaleDraw
    {
    public:
        DistroScaleDraw(Qt::Orientation orientation, const QStringList &labels)
            : d_labels(labels)
        {
            //设置间距、中间刻度、主刻度
            setTickLength(QwtScaleDiv::MinorTick, 0);
            setTickLength(QwtScaleDiv::MediumTick, 0);
            setTickLength(QwtScaleDiv::MajorTick, 5);
    
            //不显示主轴线
            enableComponent(QwtScaleDraw::Backbone, false);
    
            //设置旋转角度、对齐方式
            double rotation = (orientation == Qt::Vertical) ? -10.0 : -10.0;
            setLabelRotation(rotation);
            setLabelAlignment(Qt::AlignVCenter);
        }
    
        //用于显示文本
        virtual QwtText label(double value) const
        {
            QwtText text("");
            int index = static_cast(value); //qRound(value);
            if (index >= 0 && index < d_labels.size())
                text = d_labels[index];
    
            return text;
        }
    
    private:
        QStringList d_labels;
    };
    #include 
    class DistroChartItem: public QwtPlotBarChart
    {
    public:
        DistroChartItem(): QwtPlotBarChart()
        {
            setLegendMode(QwtPlotBarChart::LegendBarTitles);
            //设置项大小
            setLegendIconSize(QSize(15, 15));
        }
    
        void addDistro(const QString &distro, const QColor &color )
        {
            d_colors += color;
            d_distros += distro;
            itemChanged();
        }
    
        //用于显示设置项
        virtual QwtColumnSymbol *specialSymbol(int index, const QPointF &) const
        {
            //自定义项符号线度、样式、背景色
            QwtColumnSymbol *symbol = new QwtColumnSymbol(QwtColumnSymbol::Box);
            symbol->setLineWidth(5);
            symbol->setFrameStyle(QwtColumnSymbol::Raised);
    
            QColor color(Qt::white);
            if (index >= 0 && index < d_colors.size())
                color = d_colors[index];
    
            symbol->setPalette(color);
        
            return symbol;
        }
    
        //用于显示设置项文本
        virtual QwtText barTitle(int sampleIndex) const
        {
            QwtText title("");
            if (sampleIndex >= 0 && sampleIndex < d_distros.size())
                title = d_distros[sampleIndex];
    
            return title;
        }
    
    private:
        QList d_colors;
        QList d_distros;
    };
    
    BarChart::BarChart(QWidget *parent):
        QwtPlot(parent)
    {
        const struct 
        {
            QString distro;
            int hits;
            QColor color;
        }
        pageHits[] =
        {
            {QString::fromLocal8Bit("扫地神僧"), 10000, QColor(0, 160, 230)},
            {QString::fromLocal8Bit("无崖子"), 9500, QColor(115, 185, 35)},
            {QString::fromLocal8Bit("萧远山"), 8888, QColor(235, 30, 35)},
            {QString::fromLocal8Bit("慕容博"), 8500, QColor(160, 70, 164)},
            {QString::fromLocal8Bit("虚竹"), 8000, QColor(255, 130, 0)},
            {QString::fromLocal8Bit("萧峰"), 7888, QColor(125, 125, 125)},
            {QString::fromLocal8Bit("段誉"), 7000, QColor(125, 125, 255)},
            {QString::fromLocal8Bit("天山童姥"), 6500, QColor(180, 255, 180)},
            {QString::fromLocal8Bit("李秋水"), 5000, QColor(135, 205, 250)},
            {QString::fromLocal8Bit("鸠摩智"), 4500, QColor(255, 175, 200)}
        };
    
        //设置标题、背景色
        setAutoFillBackground(true);
        setPalette(QColor("Linen"));
        setTitle(QStringLiteral("天龙八部十大高手排行榜"));
    
        //设置画布边框宽度、样式、圆角大小、背景色
        QwtPlotCanvas *canvas = new QwtPlotCanvas();
        canvas->setLineWidth(2);
        canvas->setFrameStyle(QFrame::Box | QFrame::Sunken);
        canvas->setBorderRadius(10);
        QPalette canvasPalette(QColor("Plum"));
        canvasPalette.setColor(QPalette::Foreground, QColor("Indigo"));
        canvas->setPalette(canvasPalette);
        setCanvas(canvas);
    
        d_barChartItem = new DistroChartItem();
    
        QVector samples;
        for (int i = 0; i < sizeof(pageHits) / sizeof(pageHits[0]); i++)
        {
            d_distros += pageHits[i].distro;
            samples += pageHits[i].hits;
            d_barChartItem->addDistro(pageHits[i].distro, pageHits[i].color);
        }
        d_barChartItem->setSamples(samples);
        d_barChartItem->attach(this);
        insertLegend(new QwtLegend());
        setOrientation(0);
        setAutoReplot(false);
    }
    
    void BarChart::setOrientation(int value)
    {
        //设置水平或垂直显示
        Qt::Orientation orientation = (value == 0) ? Qt::Vertical : Qt::Horizontal;
        int xBottomAxisId = QwtPlot::xBottom;
        int yLeftAxisId = QwtPlot::yLeft;
    
        if (orientation == Qt::Horizontal)
            qSwap(xBottomAxisId, yLeftAxisId);
    
        d_barChartItem->setOrientation(orientation);
    
        //设置X/Y轴标题、显示范围、轴线的最大间隔
        setAxisTitle(xBottomAxisId, QStringLiteral("人物"));
        setAxisMaxMinor(xBottomAxisId, 3);
        setAxisScale(xBottomAxisId, 0, d_barChartItem->dataSize() - 1, 1.0);
        setAxisScaleDraw(xBottomAxisId, new DistroScaleDraw(orientation, d_distros));
    
        setAxisTitle(yLeftAxisId, QStringLiteral("战斗力"));
        setAxisScale(yLeftAxisId, 0, 10000);
        setAxisMaxMinor(yLeftAxisId, 5);
        setAxisScaleDraw(yLeftAxisId, new QwtScaleDraw());
    
        //设置画布页边距
        plotLayout()->setCanvasMargin(5);
    
        //重新绘制
        replot();
    }
    
    //导出pdf
    void BarChart::exportChart()
    {
        QwtPlotRenderer renderer;
        renderer.exportTo(this, QStringLiteral("天龙八部十大高手排行榜.pdf"));
    }

//main.cpp
    
    #include 
    #include 
    #include 
    #include 
    #include 
    #include "barchart.h"
    
    class MainWindow: public QMainWindow
    {
    public:
        MainWindow(QWidget *parent = NULL);
    
    private:
        BarChart *d_chart;
    };
    
    MainWindow::MainWindow(QWidget *parent):
        QMainWindow(parent)
    {
        d_chart = new BarChart(this);
        setCentralWidget(d_chart);
    
        QToolBar *toolBar = new QToolBar(this);
    
        QComboBox *orientationBox = new QComboBox(toolBar);
        orientationBox->addItem("Vertical");
        orientationBox->addItem("Horizontal");
        orientationBox->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
    
        QToolButton *btnExport = new QToolButton(toolBar);
        btnExport->setText("Export");
        btnExport->setToolButtonStyle(Qt::ToolButtonTextUnderIcon);
        connect(btnExport, SIGNAL(clicked()), d_chart, SLOT(exportChart()));
    
        toolBar->addWidget(orientationBox);
        toolBar->addWidget(btnExport);
        addToolBar(toolBar);
    
        d_chart->setOrientation(orientationBox->currentIndex());
        connect(orientationBox, SIGNAL(currentIndexChanged(int)), d_chart, SLOT(setOrientation(int)));
    }
    
    int main(int argc, char *argv[])
    {
        QApplication a(argc, argv);
    
        MainWindow mainWindow;
        mainWindow.resize(600, 500);
        mainWindow.show();
    
        return a.exec();
    }

效果如下：

[![QwtPlot之绘制统计图][QwtPlot]][QwtPlot_QwtPlot]

**注：**

技术在于交流、沟通，转载请注明出处并保持作品的完整性。

作者： [╰☆奋斗ing❤孩子\`][ing]原文： [http://blog.sina.com.cn/s/blog\_a6fb6cc90102v2ef.html][http_blog.sina.com.cn_s_blog_a6fb6cc90102v2ef.html]

[QwtPlot]: http://s16.sinaimg.cn/mw690/0033AMT7zy6N0nctAiX9f&690
[QwtPlot_QwtPlot]: /images/20220609/1f96eaa07b1e4a3282582d5fdde62555.png
[ing]: http://blog.sina.com.cn/liang19890820
[http_blog.sina.com.cn_s_blog_a6fb6cc90102v2ef.html]: http://blog.sina.com.cn/s/blog_a6fb6cc90102v2ef.html