qt画圆，QT圆的中点生成算法 ，自己设定圆心和半径，应用中点算法生成圆弧或者圆。

青色烟雨,孤影等你归来。

Mainwindow.h中添加
#include <QPainter>
void paintEvent(QPaintEvent*);
在mainwindow.cpp中添加
void MainWindow::paintEvent(QPaintEvent *)
{
        QPainter painter(this);
        painter.setPen(QPen(Qt::black,1,Qt::SolidLine,Qt::RoundCap));
        int x0=0,y,r=100;
        int x;
        float d,d0;
        d0=5.0/4.0-r;
        x=x0;
        y=r;
        d=d0;
        while(x<y)
        {
            if(d>0)
            {
                d=d+2*(x-y)+5;
                x+=1;
                y=y-1;
      }
             else
            {
                d=d+2*x+3;
                x+=1;
   }
         painter.drawPoint(x+100,y+100);
        painter.drawPoint(y+100,x+100);
        painter.drawPoint(x+100,-y+100);
          painter.drawPoint(-x+100,y+100);
        painter.drawPoint(-y+100,x+100);
         painter.drawPoint(y+100,-x+100);
        painter.drawPoint(-y+100,-x+100);
        painter.drawPoint(-x+100,-y+100);
        }

}