Qt中QPainter与坐标
SongpingWang 人气:2一、坐标系统与坐标变换
坐标系统
QPainter坐标变换相关函数
分组 | 函数原型 | 功能 |
---|---|---|
坐标变换 | void translate(qreal dx,qreal dy) | 坐标系统一定的偏移量,坐标原点平移到新的点 |
void rotate(qreal angle) | 坐标系统顺时针旋转-一个角度 | |
void scale(qreal sx,qreal sy) | 坐标系统缩放 | |
void shear(qrael sh,qreal sy) | 坐标系统做扭转变换 | |
状态保存与恢复 | void save() | 保存painter当前的状态,就是将当前状态压入栈 |
void restore() | 恢复上一次状态,就是从堆栈中弹出上次的状态 | |
void resetTransform() | 复位所有的坐标变换 |
示例
绘制五角星
船舰widget窗口,只重载paintEvent
函数
#include "widget.h" #include "ui_widget.h" #include <QPalette> #include <QPainter> #include <cmath> Widget::Widget(QWidget *parent) : QWidget(parent) , ui(new Ui::Widget) { ui->setupUi(this); setPalette(QPalette(Qt::white)); setAutoFillBackground(true); resize(600,300); } Widget::~Widget() { delete ui; } void Widget::paintEvent(QPaintEvent *event) { Q_UNUSED(event); QPainter painter(this); QPen pen; //笔 pen.setStyle(Qt::SolidLine); painter.setPen(pen); painter.setRenderHint(QPainter::Antialiasing); //抗锯齿 QBrush brush; //刷子 brush.setColor(Qt::yellow); brush.setStyle(Qt::SolidPattern); painter.setBrush(brush); //qreal deg = 3.141592*2/5; qreal deg = (360/5)*3.141592/180; qreal R=100; QPoint points[5] = { QPoint(R,0), QPoint(R*std::cos(deg),-R*std::sin(deg)), QPoint(R*std::cos(2*deg),-R*std::sin(2*deg)), QPoint(R*std::cos(3*deg),-R*std::sin(3*deg)), QPoint(R*std::cos(4*deg),-R*std::sin(4*deg)), }; QPainterPath starPath; starPath.moveTo(points[3]); starPath.lineTo(points[1]); starPath.lineTo(points[4]); starPath.lineTo(points[2]); starPath.lineTo(points[0]); starPath.closeSubpath(); QFont font; font.setPointSize(12); starPath.addText(points[0], font, "0"); starPath.addText(points[1], font, "1"); starPath.addText(points[2], font, "2"); starPath.addText(points[3], font, "3"); starPath.addText(points[4], font, "4"); painter.setFont(font); painter.save(); //保存 painter.translate(100,120); painter.drawPath(starPath); painter.drawText(0,0,"S1"); painter.restore(); //恢复 painter.translate(300,120); painter.rotate(90); painter.scale(0.7,0.7); painter.drawPath(starPath); painter.drawText(0,0,"S2"); painter.resetTransform(); painter.translate(500,120); painter.rotate(-90); painter.scale(1.05,1.05); painter.drawPath(starPath); painter.drawText(0,0,"S3"); }
二、可缩放图形
视口: 绘图设备的任意一个矩形区域的物理坐标,可以只选取物理坐标的一个矩形区域用
于绘图。视口默认情况下等于绘图设备的整个矩形区。
窗口: 对应于视口的矩形区域,只不过是用逻辑坐标定义的坐标系,窗口坐标的中心在矩
形中心。
使用窗口坐标绘制,不用管实际的物理大小
#include "widget.h" #include "ui_widget.h" #include <QPalette> #include <QPainter> #include <QLinearGradient> Widget::Widget(QWidget *parent) : QWidget(parent) , ui(new Ui::Widget) { ui->setupUi(this); setPalette(QPalette(Qt::white)); setAutoFillBackground(true); resize(300,300); } Widget::~Widget() { delete ui; } void Widget::paintEvent(QPaintEvent *event) { Q_UNUSED(event); QPainter painter(this); painter.setRenderHint(QPainter::Antialiasing); int W = QWidget::width(); int H = QWidget::height(); int side = qMin(W,H); QRect rect((W-side)/2,(H-side)/2, side,side); //视口大小 painter.drawRect(rect); painter.setViewport(rect); painter.setWindow(-100,-100,200,200); QLinearGradient linerGradient(0,0,100,0); // 渐变 linerGradient.setColorAt(0,Qt::yellow); linerGradient.setColorAt(1,Qt::green); linerGradient.setSpread(QGradient::PadSpread); //发散 painter.setCompositionMode(QPainter::RasterOp_NotSourceXorDestination); painter.setBrush(linerGradient); for (size_t i=0; i<36; i++) { painter.drawEllipse(QPoint(50,0),50,50); painter.rotate(10); } }
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