Qt绘图之画家QPainter

QPainter在使用时需要使用构造函数，立马指定在哪个控件上进行绘制

[explicit] QPainter::QPainter(QPaintDevice *device)

画点

• 可以1次画1个点

//准备4个点
QPoint  points[4]{
  QPoint(10, 80),
  QPoint(20, 10),
  QPoint(80, 30),
  QPoint(90, 70) };

//一次画1个点
 painter.drawPoint(points[1]);

• 也可以一次性画多个点

 

            //准备4个点
            QPoint  points[4]{
                QPoint(10, 80),
                QPoint(20, 10),
                QPoint(80, 30),
                QPoint(90, 70) };

            //一次画多个点
            painter.drawPoints(points,4);

画线

两个点确定一条线

• 1次画1条

            //准备4个点
            QPoint  points[4]{
                QPoint(10, 80),
                QPoint(20, 10),
                QPoint(80, 30),
                QPoint(90, 70) };

            //画一条线
            painter.drawLine(points[0],points[2]);

• 1次画多条

            //准备4个点
            QPoint  points[4]{
                QPoint(10, 80),
                QPoint(20, 10),
                QPoint(80, 30),
                QPoint(90, 70) };

            //一次画多条线，直接使用初始化列表{}
            painter.drawLines({QLineF(points[0],points[1]),QLineF(points[2],points[3])});

画多线段（Polyline）

相关API

//带F为小数版本
// 参1：点的数组，参2：点的个数
void drawPolyline(const QPointF *points, int pointCount)
// 参数：多边形
void drawPolyline(const QPolygonF &points)

//整数版本
void drawPolyline(const QPoint *points, int pointCount)
void drawPolyline(const QPolygon &points)

 

             //准备4个点
            QPoint  points[4]{
                QPoint(10, 80),
                QPoint(20, 10),
                QPoint(80, 30),
                QPoint(90, 70) };

    painter.drawPolyline(points,4);
  //也可以这样
  //painter.drawPolyline(QPolygon({QPoint(100, 80),QPoint(110, 10),QPoint(220, 10)}));

 画多边形（Polygon）

相关API

void drawPolygon(const QPointF *points,
                 int pointCount,
                 Qt::FillRule fillRule = Qt::OddEvenFill);
void drawPolygon(const QPolygonF &points,
                 Qt::FillRule fillRule = Qt::OddEvenFill);

void drawPolygon(const QPoint *points,
                 int pointCount,
                 Qt::FillRule fillRule = Qt::OddEvenFill);
void drawPolygon(const QPolyg