Qt绘制曲线图（基于qt画图QPainter）

在没有QCharst模块时，可以使用QPainter自定义绘制曲线折线图

下面提供完整代码供参考：
直接在qt创建一个QMainWindow类的app的工程,不自动生成ui文件，然后把下面代码复制到mainwindow.cpp编译运行即可。
mainwindow.cpp:

#include"mainwindow.h"#include<QPainter>#include<QLabel>#include<QImage>#include<QPixmap>//使用QPainter将数据到曲线画在图片中
QImage imageCurve(const QVector<int>&data1,const QVector<int>&data2);MainWindow::MainWindow(QWidget *parent):QMainWindow(parent){resize(800,600);int n=10;//n为数据个数
    QVector<int> data1;
    QVector<int> data2;for(int i=0;i<n;i++)//随机产生两个数据集
        data1.append(rand()%20+10);for(int i=0;i<n;i++)
        data2.append(rand()%30+10);

    QLabel *label =newQLabel(this);

    label->setGeometry(50,50,600,500);//将画出来到曲线显示到label上面
    label->setPixmap(QPixmap::fromImage(imageCurve(data1,data2)));
    label->show();}MainWindow::~MainWindow(){}

QImage imageCurve(const QVector<int>&data1,const QVector<int>&data2){
    QString x_title ="x_title";//x坐标名称
    QString y_title ="y_title";//y坐标名称
    QString title ="xx title charst";//曲线图xx名称
    QString overView ="charst: test,csdn: boonion";//图内容说明

    QString data1_name ="first";//第一条曲线名称
    QString data2_name ="second";

    QImage mimage =QImage(600,500,QImage::Format_RGB32);//画布的初始化大小设为600*500，使用32位颜色
    QColor backColor =qRgb(255,255,255);//画布初始化背景色使用白色
    mimage.fill(backColor);//对画布进行填充

    QPainter painter(&mimage);

    painter.setRenderHint(QPainter::Antialiasing,true);//设置反锯齿模式，好看一点int pointx=30,pointy=420;//确定坐标轴起点坐标，这里定义(35,280)int width=560-pointx,height=280;//确定坐标轴宽度跟高度

    painter.drawLine(pointx,pointy,width+pointx,pointy);//坐标轴x宽度为width
    painter.drawLine(pointx,pointy-height,pointx,pointy);//坐标轴y高度为heightint n=data1.size();//n为第一个数据集个数int m = data2.size();int max=0;//数组里的最大值for(int i =0; i < n; i++){if(data1[i]> max){
            max = data1[i];}}for(int i =0; i < m; i++){if(data2[i]> max){
            max = data2[i];}}double kx=(double)width/(n-1);//x轴的系数double ky=(double)height/max;//y方向的比例系数//设置两条的画笔
    QPen pen,penPoint;
    pen.setColor(Qt::green);
    pen.setWidth(2);

    penPoint.setColor(Qt::blue);
    penPoint.setWidth(5);

    QPen penOther,penPointOther;
    penOther.setColor(Qt::yellow);
    penOther.setWidth(2);

    penPointOther.setColor(Qt::red);
    penPointOther.setWidth(5);for(int i=0;i<n-1;i++)//画第一条线{if(i+1> n-1)break;//由于y轴是倒着的，所以y轴坐标要pointy-a[i]*ky 其中ky为比例系数
        painter.setPen(pen);//用于连线
        painter.drawLine(pointx+kx*i,pointy-data1[i]*ky,pointx+kx*(i+1),pointy-data1[i+1]*ky);
        painter.setPen(penPoint);//蓝色的笔，用于标记各个点
        painter.drawPoint(pointx+kx*i,pointy-data1[i]*ky);
        painter.drawText(pointx+kx*i,pointy-data1[i]*ky-4,QString::number(data1[i]));}if(!data1.isEmpty())
        painter.drawPoint(pointx+kx*(n-1),pointy-data1[n-1]*ky);//绘制最后一个点//画线图示
    painter.setPen(pen);
    painter.drawLine(pointx+width-50,pointy-height-50,pointx+width-25,pointy-height-50);
    painter.setPen(penPoint);
    painter.drawPoint(pointx+width-25,pointy-height-50);
    painter.setPen(pen);
    painter.drawLine(pointx+width-20,pointy-height-50,pointx+width,pointy-height-50);
    painter.setPen(Qt::black);
    painter.drawText(pointx+width-40,pointy-height-30,QString("%1").arg(data1_name));for(int i=0;i<m-1;i++){if(i+1> m-1)break;

        painter.setPen(penOther);
        painter.drawLine(pointx+kx*i,pointy-data2[i]*ky,pointx+kx*(i+1),pointy-data2[i+1]*ky);
        painter.setPen(penPointOther);
        painter.drawPoint(pointx+kx*i,pointy-data2[i]*ky);
        painter.drawText(pointx+kx*i,pointy-data2[i]*ky-5,QString::number(data2[i]));}if(!data2.isEmpty())
         painter.drawPoint(pointx+kx*(m-1),pointy-data2[m-1]*ky);//绘制最后一个点//画线图示
    painter.setPen(penOther);
    painter.drawLine(pointx+width-50,pointy-height-100,pointx+width-25,pointy-height-100);
    painter.setPen(penPointOther);
    painter.drawPoint(pointx+width-25,pointy-height-100);
    painter.setPen(penOther);
    painter.drawLine(pointx+width-20,pointy-height-100,pointx+width,pointy-height-100);
    painter.setPen(Qt::black);
    painter.drawText(pointx+width-40,pointy-height-80,QString("%1").arg(data2_name));//绘制刻度线int tmp = n > m ? n : m;//取刻度最大的分度值int xn = tmp >16?16: tmp;int yn = max >20?20: max;

    QPen penDegree;
    penDegree.setColor(Qt::black);
    penDegree.setWidth(2);
    painter.setPen(penDegree);//画上x轴刻度线for(int i=0;i<xn;i++)//分成dn份{//选取合适的坐标，绘制一段长度为4的直线，用于表示刻度

        painter.drawLine(pointx+(i+1)*width/xn,pointy,pointx+(i+1)*width/xn,pointy+4);
        painter.drawText(pointx+(i)*width/xn,
                         pointy+15,QString::number((int)((i)*((double)tmp/xn))));}//画xy刻度名称
    painter.setPen(Qt::black);
    painter.drawText(pointx+width-40,pointy+30,QString("%1").arg(x_title));
    painter.setPen(Qt::black);
    painter.drawText(pointx-10,pointy-height-30,QString("%1").arg(y_title));//y轴刻度线double _maStep=(double)max/yn;//y轴刻度间隔需根据最大值来表示for(int i=0;i<yn;i++){//主要就是确定一个位置，然后画一条短短的直线表示刻度。
        painter.drawLine(pointx,pointy-(i+1)*height/yn,
                         pointx-4,pointy-(i+1)*height/yn);
        painter.drawText(pointx-20,pointy-(i+0.85)*height/yn,QString::number((int)(_maStep*(i+1))));}//画图内容说明
    QStringList strlist = overView.split(',');//分割字符串
    painter.setPen(Qt::gray);int t_h =100;foreach(QString str,strlist){
      painter.drawText(pointx+40,pointy-height-t_h,QString("%1").arg(str));
      t_h -=20;}//画标题
    painter.setPen(Qt::black);
    QFont font;
    font.setPixelSize(20);
    painter.setFont(font);
    painter.drawText(pointx+width/2-80,pointy-height-60,QString("%1").arg(title));return mimage;}//博客：booinon//https://blog.csdn.net/boonion?spm=1011.2415.3001.5343

//博客：booinon
//https://blog.csdn.net/boonion?spm=1011.2415.3001.5343