QT绘图应用2：利用Qt绘制直方图和分位数图

废话不说，直接上图

我想绘制如上所示的图，我该怎么办？？？

下面给出思路:

1,画坐标系 drawLine函数搞定  （有人问我画带箭头的线如何搞定，你在端点再画两条斜着的线不就可以了）

2 画标度  通过drawLine画出那些短线，通过drawText画出数字，具体的位置可以通过循环来做

3 直方图 很明显，都是一系列的矩形组成的，通过drawRect函数就可以实现了

4 离散点 通过drawEclipse函数 画出一个个小的圆就可以了

5 坐标映射  把你想要画的数据通过各种方法映射到你的坐标系上面去，这点学过小学数学的人都应该会明白 （这点是至关重要的），就是在画线和画矩形的时候把相关参数和实际的参数关联起来！

下面给出实例代码，大家可以参考一下

    QImage image;
    image.load("d:/res.jpg");
    QPainter painter(&image);
    //通过以上代码已经获得了句柄，可以进行操作了
    //绘制直方图
    painter.drawLine(50,400,350,400);
    painter.drawLine(50,400,50,100-20);
    painter.drawLine(50,100-20,45,105-20);   //上箭头
    painter.drawLine(50,100-20,55,105-20);   //上箭头
    painter.drawLine(345,395,350,400);   //右箭头
    painter.drawLine(345,405,350,400);   //右箭头
    painter.drawText(QPoint(330,420),"column diagram");
    int virable = 400;
    for(int i=-1;i<10;i++){               //绘制向上坐标
        painter.drawLine(50,virable,53,virable);
        painter.drawText(QPoint(40,virable),QString::number(i+1));
        virable-=30;
    }
    painter.drawText(QPoint(90,420),"10~13");
    painter.drawText(QPoint(170,420),"14~17");
    painter.drawText(QPoint(250,420),"18~20");
    virable = 70;
    for(int i=0;i<3;i++){
        painter.drawRect(virable,400-R.num1[i]*30,30,R.num1[i]*30);
        painter.drawRect(virable+30,400-R.num2[i]*30,30,R.num2[i]*30);
        virable +=80;
    }

    //绘制分位数图
    painter.drawLine(450,400,750,400);
    painter.drawLine(450,400,450,100-20);
    painter.drawLine(450,100-20,445,105-20);   //上箭头
    painter.drawLine(450,100-20,455,105-20);   //上箭头
    painter.drawLine(745,395,750,400);   //右箭头
    painter.drawLine(745,405,750,400);   //右箭头
    painter.drawText(QPoint(730,420),"quantile plot");
    virable = 400;
    for(int i=-1;i<10;i++){               //绘制向上坐标
        painter.drawLine(450,virable,453,virable);
        painter.drawText(QPoint(440,virable),QString::number(i+11));
        virable-=30;
    }
    virable = 450;
    for(float k=0;k<=1.1;k+=0.25){               //绘制向右坐标
        painter.drawLine(virable,400,virable,400+3);
        painter.drawText(QPoint(virable,420),QString::number(k));
        virable+=70;
    }
    // 画出分位图的点
    int count_a = 0,count_b = 0;
    for(int i = 10;i<=20;i++){
       /* if(R.re1[i]>0){
            for(int j=0;j<R.re1[i];j++){
                count_a++;
                painter.drawEllipse(450+((float)count_a/A_AMOUNT)*280,400-(i-10)*30,5,5);
            }
        }*/
        if(R.re2[i]>0){
            for(int k=0;k<R.re2[i];k++){
                count_b++;
                painter.drawEllipse(450+((float)count_b/B_AMOUNT)*280,400-(i-10)*30,5,5);
            }
        }
    }


    ui->label->setGeometry(10,10,1200,700);
    QImage resultImg = image.scaled(ui->label->size(),Qt::KeepAspectRatio,Qt::SmoothTransformation);
    ui->label->setPixmap(QPixmap::fromImage(resultImg));
    ui->label->show();