Qt之qcustomplot绘图总结

首先我用customplot的时候需要先知道它内部类的使用方式和作用，比如以下的图像部分：
QCPGraph ：折线图
QCPCurve：用于曲线图，可以有循环
QCPBars：柱形图，如果有多个QCPBars ，可以依次重叠
QCPStatisticalBox（需实例化）：盒子图
QCPColorMap（实例化）：色谱图
QCPFinancial（实例化）：金融图
QCPAbstractItem：标示项
包括：
QCPItemStraightLine：直线
QCPItemLine：线段
QCPItemCurve：曲线
QCPItemRect：矩形
QCPItemEllipse：椭圆
QCPItemText：文本
QCPItemTracer：小圆球
QCPItemPixmap：图片
QCPItemBracket：括弧

布局项(QCPLayoutElement)：布局项(QCPAbstractLegendItem)、坐标轴矩形(QCPAxisRect)
网格线(QCPGrid)：每一个坐标轴对应一个网格线
坐标轴(QCPAxis)：一个坐标轴矩形包含四个坐标轴，上下左右四个坐标轴。

简易demo：

void MainWindow::setupSimpleDemo(QCustomPlot *customPlot)
{
  demoName = "Simple Demo";

  // add two new graphs and set their look:
  customPlot->addGraph();
  customPlot->graph(0)->setPen(QPen(Qt::blue)); // line color blue for first graph
  customPlot->graph(0)->setBrush(QBrush(QColor(0, 0, 255, 20))); // first graph will be filled with translucent blue
  customPlot->addGraph();
  customPlot->graph(1)->setPen(QPen(Qt::red)); // line color red for second graph
  // generate some points of data (y0 for first, y1 for second graph):
  QVector<double> x(250), y0(250), y1(250);
  for (int i=0; i<250; ++i)
  {
    x[i] = i;
    y0[i] = qExp(-i/150.0)*qCos(i/10.0); // exponentially decaying cosine
    y1[i] = qExp(-i/150.0);              // exponential envelope
  }

  customPlot->xAxis->setRange(0, 250);
  customPlot->xAxis->setAutoTickStep(false);
  customPlot->xAxis->setTickStep(25);
  customPlot->xAxis->setAutoSubTicks(false);
  customPlot->xAxis->setSubTickCount(9);
  customPlot->yAxis->setRange(0, 10);

  // configure right and top axis to show ticks but no labels:
  // (see QCPAxisRect::setupFullAxesBox for a quicker method to do this)
  customPlot->xAxis2->setVisible(true);
  customPlot->xAxis2->setTickLabels(false);
  customPlot->yAxis2->setVisible(true);
  customPlot->yAxis2->setTickLabels(false);
  // make left and bottom axes always transfer their ranges to right and top axes:
  connect(customPlot->xAxis, SIGNAL(rangeChanged(QCPRange)), customPlot->xAxis2, SLOT(setRange(QCPRange)));
  connect(customPlot->yAxis, SIGNAL(rangeChanged(QCPRange)), customPlot->yAxis2, SLOT(setRange(QCPRange)));
  // pass data points to graphs:
  customPlot->graph(0)->setData(x, y0);
  customPlot->graph(1)->setData(x, y1);
  // let the ranges scale themselves so graph 0 fits perfectly in the visible area:
  customPlot->graph(0)->rescaleAxes();
  // same thing for graph 1, but only enlarge ranges (in case graph 1 is smaller than graph 0):
  customPlot->graph(1)->rescaleAxes(true);
  // Note: we could have also just called customPlot->rescaleAxes(); instead
  // Allow user to drag axis ranges with mouse, zoom with mouse wheel and select graphs by clicking:
  customPlot->setInteractions(QCP::iRangeDrag | QCP::iRangeZoom | QCP::iSelectPlottables);
}