如何为大型xAxis的QBarChart添加滚动条

Question

我正在用灰度图像中每个像素的计数来制作直方图。这意味着我的条形图上有255条。它看起来像下面，我不能让它扩张。

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这就是我写的代码：

Histogram::Histogram()
{
    ui = std::make_unique<Ui_GraphWindow>();
    ui->setupUi(this);
    setAttribute(Qt::WA_DeleteOnClose, true); // delete the object after the window is closed


    ui->chartView->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOn);
    ui->chartView->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOn);        
}

void Histogram::display(QImage * image)
{
    show();

    std::map<size_t, size_t> colorCount;    
    for (int i = 0; i < 256; i++) {
        colorCount[i] = 0;
    }

    for (int i = 0; i < image->width(); i++) {
        for (int j = 0; j < image->height(); j++) {
            auto val = qGray(image->pixel(i, j));
            colorCount[val]++;
        }
    }
    QStringList categories;


    std::vector<QBarSet*> sets(colorCount.size());
    QBarSeries *series = new QBarSeries();

    for (int i = 0; i < colorCount.size(); i++) {
        sets[i] = new QBarSet(std::to_string(i).c_str());

        *sets[i] << colorCount[i];
        sets[i]->setColor(QColor(i, i, i));
        sets[i]->setBorderColor(QColor(255, 255, 255));
        series->append(sets[i]);
    }

    QChart *chart = new QChart();
    chart->addSeries(series);
    chart->setTitle("Simple barchart example");
    chart->setAnimationOptions(QChart::SeriesAnimations);

    QBarCategoryAxis *axis = new QBarCategoryAxis();
    chart->createDefaultAxes();
    axis->append(categories);
    chart->setAxisX(axis, series);

    chart->legend()->setVisible(false);
    ui->chartView->setChart(chart);
    ui->chartView->setRenderHint(QPainter::Antialiasing);
}

即使我添加了滚动条，它也不起作用。我想要能够水平滚动。我试着使用zoomIn()，但它没有工作，scale()确实使它更大，但是没有滚动条出现，我只能看到图表的一部分。

Answer 1

chart->legend()->setVisible(false);
ui->chartView->setRenderHint(QPainter::Antialiasing);
// the magic is done with setRubberBand()
chartView->setRubberBand(QChartView::HorizontalRubberBand);
ui->chartView->setChart(chart); //try this if the other one does not work with your version of qt:  chartView->setParent(ui->histoPlot);

如果按下鼠标左键并启用橡皮筋，.橡皮筋显示在屏幕上。这使用户能够使用鼠标真正选择缩放区域。看看我在这里的意思，动作和结果 --如何回到我们所选择的未扩展的主要区域？只需按几次鼠标的严格按钮。

此外，如果添加更多关于X轴的详细信息，它将更具可读性：

axisX = new QValueAxis();
chart->addAxis(axisX, Qt::AlignBottom); // Add a horizontal X axis at the bottom of the chart
    barseries->attachAxis(axisX);
    axisX->applyNiceNumbers();
          
// Setting Range to be precise of making the whole data visible
    axisX->setRange(0,256); // because you have a histogram