QT-坐标系统和坐标变换-绘制曲线应用程序示例

#include "widget.h" #include "ui_widget.h" #include <QtMath> #include <QPainter> #include <QFontMetrics> void Widget::iniData() {//生成实际数据 qreal t=0; qreal w=4; for (int i=0;i<m_count;i++) { m_dataF.append(QPointF(t,qSin(w*t))); t+=m_intv; } } void Widget::preparePoints(QRect &windRect) { m_points.clear(); int xPos,yPos; qreal x,y; for (int i=0;i<m_count;i++) { x=m_dataF[i].x(); //实数 y=m_dataF[i].y();//实数 xPos=m_xRatio*(x-m_xmin); xPos=m_margins.left()+xPos; yPos=m_yRatio*(y-m_ymin); yPos=windRect.height()-m_margins.bottom()-yPos; m_points.append(QPoint(xPos,yPos)); } } void Widget::drawGrid(QPainter &p, QRect &windRect) { QRect rect(windRect.left()+m_margins.left(), windRect.top()+m_margins.top(), windRect.width()-m_margins.left()-m_margins.right(), windRect.height()-m_margins.top()-m_margins.bottom()); if (!rect.isValid()) return; QPen penDot(Qt::DotLine); penDot.setColor(Qt::gray); QPen penSolid(Qt::SolidLine); penSolid.setColor(Qt::black); // pen.setColor(this->palette().light().color()); p.setPen(penSolid); p.drawRect(rect.adjusted(0,0,-1,-1)); int Xpos; qreal Xvalue; QString xlab; QFontMetrics textSize(this->font()); QRect textRect; for(int i=0;i<=m_XTicks;i++) { Xpos=rect.left()+i*m_xRatio; // Xvalue=m_xmin+i*m_xspan/m_XTicks;// p.setPen(penDot); p.drawLine(Xpos,rect.top(),Xpos,rect.bottom()); p.setPen(penSolid); p.drawLine(Xpos,rect.bottom(),Xpos,rect.bottom()+5); xlab=QString::asprintf("%.1f",Xvalue); textRect=textSize.boundingRect(xlab);//得到字符串的rect p.drawText(Xpos-textRect.width()/2, rect.bottom()+5+textRect.height(), xlab); } xlab="time(sec)"; textRect=textSize.boundingRect(xlab);//得到字符串的rect p.drawText(rect.left()+(rect.width()-textRect.width())/2, windRect.bottom()-textRect.height()/2, xlab); xlab="曲线绘图"; textRect=textSize.boundingRect(xlab);//得到字符串的rect p.drawText(rect.left()+(rect.width()-textRect.width())/2, (m_margins.top()-textRect.height())/2+textRect.height(), xlab); int Ypos; qreal Yvalue; QString ylab; for(int i=0;i<=m_YTicks;i++) { Ypos=rect.bottom()-i*m_yRatio; // Yvalue=m_ymin+i*m_yspan/m_YTicks;// p.setPen(penDot); p.drawLine(rect.left(),Ypos,rect.right(),Ypos); p.setPen(penSolid); p.drawLine(rect.left()-5,Ypos,rect.left(),Ypos); ylab=QString::asprintf("%.1f",Yvalue); textRect=textSize.boundingRect(ylab);//得到字符串的rect p.drawText(rect.left()-10-textRect.width(), Ypos+textRect.height()/2, ylab); } ylab="函数值"; textRect=textSize.boundingRect(ylab);//得到字符串的rect p.save(); p.translate(0,windRect.height()/2); //平移到左侧中心 p.rotate(-90);//逆时针旋转90度，变成正北为X轴，正东为Y轴 p.drawText(-textRect.width()/2, (m_margins.left()-textRect.height())/2, ylab); p.restore(); } void Widget::drawCurve(QPainter &p, QRect &windRect) { QPolygon curve(m_points.count()); for(int i=0;i<m_points.count();i++) curve[i]=m_points[i]; QPen penSolid(Qt::SolidLine); penSolid.setColor(Qt::blue); penSolid.setWidth(2); p.setPen(penSolid); p.drawPolyline(curve); } void Widget::paintEvent(QPaintEvent *event) { QPainter p(this); p.setRenderHint(QPainter::Antialiasing,true); p.setRenderHint(QPainter::TextAntialiasing,true); int W=this->width();// int H=this->height();// QRect WindRect(0,0,W,H); // p.setWindow(WindRect);//1:1设置窗口，但是远点在中心点 m_xRatio=(W-m_margins.left()-m_margins.right())/m_xspan; m_yRatio=(H-m_margins.top()-m_margins.bottom())/m_yspan; drawGrid(p,WindRect); preparePoints(WindRect); drawCurve(p,WindRect); } Widget::Widget(QWidget *parent) : QWidget(parent), ui(new Ui::Widget) { ui->setupUi(this); m_margins.setLeft(80); m_margins.setTop(50); m_margins.setRight(50); m_margins.setBottom(50); // m_margins=new QMargins(50,50,50,50);//QMargins(int left, int top, int right, int bottom) setPalette(QPalette(Qt::white)); // this->setBackgroundRole(QPalette::Dark); //QPalette::Window,QPalette::Dark setAutoFillBackground(true); iniData(); } Widget::~Widget() { delete ui; }