QT绘制贝塞尔曲线及控制点

#include "beziercurve.h" #include <QtMath> #include <QComboBox> #include <QHBoxLayout> #include <QLabel> #include <QMouseEvent> #include <QPainter> #include <QPainterPath> /** * @brief createNBezierCurve 生成N阶贝塞尔曲线点 * @param src 源贝塞尔控制点 * @param dest 目的贝塞尔曲线点 * @param precision 生成精度 */ static void createNBezierCurve(const QList<QPointF> &src, QList<QPointF> &dest, qreal precision) { if (src.size() <= 0) return; //清空 QList<QPointF>().swap(dest); for (qreal t = 0; t < 1.0000; t += precision) {//根据精度绘制点 int size = src.size(); QVector<qreal> coefficient(size, 0); coefficient[0] = 1.000; qreal u1 = 1.0 - t; for (int j = 1; j <= size - 1; j++) { qreal saved = 0.0; for (int k = 0; k < j; k++){ qreal temp = coefficient[k]; coefficient[k] = saved + u1 * temp; saved = t * temp; } coefficient[j] = saved; } QPointF resultPoint; for (int i = 0; i < size; i++) { QPointF point = src.at(i); resultPoint = resultPoint + point * coefficient[i]; } //给贝塞尔曲线加入关键点 dest.append(resultPoint); } } class BezierCurvePrivate { public: BezierCurvePrivate() = default; //完成控制点构成 bool m_completed = false; bool m_mousePressed = false; int m_currentControlPointIndex = -1; qreal m_precision = 0.1; QList<QPointF> m_controlPoints; QList<QPointF> m_bezierCurve; }; BezierCurve::BezierCurve(QWidget *parent) : QWidget(parent) { d = new BezierCurvePrivate; //贝塞尔曲线类 QComboBox *comboBox = new QComboBox(this); connect(comboBox, QOverload<int>::of(&QComboBox::activated), this, [=](int index) { d->m_precision = comboBox->itemText(index).toDouble(); createNBezierCurve(d->m_controlPoints, d->m_bezierCurve, d->m_precision);//更新贝塞尔曲线 线上的点 update(); }); comboBox->addItem(QString::number(0.1)); comboBox->addItem(QString::number(0.01)); comboBox->addItem(QString::number(0.001)); QLabel *label = new QLabel("精度:", this); QHBoxLayout *layout = new QHBoxLayout; layout->addWidget(label); layout->addWidget(comboBox); QWidget *widget = new QWidget(this); widget->resize(150, 50); widget->setLayout(layout); resize(800, 600); } BezierCurve::~BezierCurve() { if (d) delete d; } void BezierCurve::paintEvent(QPaintEvent *event) { Q_UNUSED(event); //即Q_UNUSED()函数在程序中没有实质性的作用，用来避免编译器警告 QPainter painter(this);//绘制控制点 painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing); painter.save(); painter.setBrush(QBrush(Qt::green)); QFontMetrics metrics(painter.font());//字体规格信息 for (auto i = 0; i < d->m_controlPoints.size(); i++) { painter.setPen(Qt::green); painter.drawEllipse(d->m_controlPoints.at(i), 6.0, 6.0);//控制点大小 //QString number = QString::number(i); //auto rect = metrics.boundingRect(number); //painter.drawText(d->m_controlPoints.at(i) + QPointF(-rect.width() / 2, rect.height() / 2 - 1.0), number); } painter.restore();//恢复上面保存的状态 if (d->m_controlPoints.size() >= 2) {//如果控制点大于2个，绘制贝塞尔曲线 QPainterPath curve; curve.moveTo(d->m_bezierCurve.at(0)); for (auto i = 1; i < d->m_bezierCurve.size(); i++) {; curve.lineTo(d->m_bezierCurve.at(i)); } auto pen = painter.pen(); pen.setColor(Qt::blue); pen.setWidth(2.0); painter.setPen(pen); painter.drawPath(curve); } } void BezierCurve::mousePressEvent(QMouseEvent *event) //绘制控制点功能 { //event->buttons()返回产生事件的按钮状态，函数返回当前按下的所有按钮，按钮状态可以是Qt::LeftButton,Qt::RightButton,Qt::MidButton或运算组合 if (event->buttons() & Qt::LeftButton && event->pos().y() > 50) { d->m_mousePressed = true; //鼠标按下 if (d->m_completed) { //如果已经完成绘制 d->m_currentControlPointIndex = -1; //当前控制点序号 auto pos = event->pos(); for (auto i = 0; i < d->m_controlPoints.size(); i++) { auto point = d->m_controlPoints.at(i); //判断是否在控制点上 if (qAbs(qSqrt(qPow(pos.x() - point.x(), 2) + qPow(pos.y() - point.y(), 2))) < 10.0000) { d->m_currentControlPointIndex = i; break; } } } else { //如果没有完成绘制，则添加控制点 d->m_controlPoints.append(event->pos()); //控制点增加了，需要更新 createNBezierCurve(d->m_controlPoints, d->m_bezierCurve, d->m_precision); update();//update函数的作用是更新窗口 } } else if (event->buttons() & Qt::RightButton) { //如果按下右键，停止绘制 d->m_completed = true; } } void BezierCurve::mouseMoveEvent(QMouseEvent *event) { if (event->buttons() & Qt::LeftButton && d->m_mousePressed && d->m_currentControlPointIndex != -1 && event->pos().y() > 50) { //如果鼠标左键按住移动 if (d->m_currentControlPointIndex < d->m_controlPoints.size()) { d->m_controlPoints[d->m_currentControlPointIndex] = event->pos();//更新当前控制点位置 createNBezierCurve(d->m_controlPoints, d->m_bezierCurve, d->m_precision); update(); } } } void BezierCurve::mouseReleaseEvent(QMouseEvent *event) { d->m_currentControlPointIndex = -1; if (event->buttons() & Qt::LeftButton) { //鼠标左键松开 d->m_mousePressed = false; } } void BezierCurve::keyPressEvent(QKeyEvent *event) { if (event->key() == Qt::Key_Escape) {//如果按esc，清除所有内容 d->m_completed = false; QList<QPointF>().swap(d->m_controlPoints); QList<QPointF>().swap(d->m_bezierCurve); update(); } }