Qt使用QPainter绘制矢量图并保存为svg文件

位图和矢量图：

Bitmap:

• Usually a larger file size
• Cannot be enlarged into a higher resolution as the image quality will be affected
• Used to display complex images with many colors, such as photographs

Vector:

• Very small in file size
• Graphics can be resized without affecting the image quality
• Only a limited amount of color can be applied to each shape (single color, gradient, or pattern)
• Complex shapes require high-processing power to be generated

新建基于Widget的应用程序，继承于QMainWindow

 MainWindow.h

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

#ifndef MAINWINDOW_H #define MAINWINDOW_H #include <QMainWindow> #include <QPainter> #include <QMenuBar> #include <QtSvg/QSvgGenerator> #include <QFileDialog> class MainWindow : public QMainWindow {     Q_OBJECT public:     MainWindow(QWidget *parent = 0);     ~MainWindow();     virtual void paintEvent(QPaintEvent *event); public slots:     void actionSaveAsSVG(); private:     void paintAll(QSvgGenerator *generator = nullptr); }; #endif // MAINWINDOW_H

 MainWindow.cpp

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75

#include "MainWindow.h" MainWindow::MainWindow(QWidget *parent)     : QMainWindow(parent) {     QMenu *fileMenu = menuBar()->addMenu(QObject::tr("&File"));     fileMenu->addAction(QObject::tr("Save As Svg"), this, &MainWindow::actionSaveAsSVG); } MainWindow::~MainWindow() { } void MainWindow::paintEvent(QPaintEvent *event) {     paintAll(); } void MainWindow::actionSaveAsSVG() {     QString filePath = QFileDialog::getSaveFileName(this, "Save SVG",                                                     "", "SVG files (*.svg)");     if (filePath == "")         return;     QSvgGenerator generator;     generator.setFileName(filePath);     generator.setSize(QSize(this->width(), this->height()));     generator.setViewBox(QRect(0, 0, this->width(), this->height()));     generator.setTitle("SVG Example");     generator.setDescription("This SVG file is generated by Qt.");     paintAll(&generator); } void MainWindow::paintAll(QSvgGenerator *generator) {     QPainter painter;     if (generator)         painter.begin(generator);     else         painter.begin(this);     // Draw Text     painter.setFont(QFont("Times", 14, QFont::Bold));     painter.drawText(QPoint(20, 40), "Hello Qt");     // Draw Line     painter.drawLine(QPoint(50, 70), QPoint(100, 100));     // Draw Rectangle     painter.setBrush(Qt::BDiagPattern);     painter.drawRect(QRect(40, 120, 80, 30));     // Draw Ellipse     QPen ellipsePen;     ellipsePen.setColor(Qt::red);     ellipsePen.setStyle(Qt::DashDotLine);     painter.setPen(ellipsePen);     painter.drawEllipse(QPoint(80, 200), 50, 20);     // Draw Rectangle     QPainterPath rectPath;     rectPath.addRect(QRect(150, 30, 100, 50));     painter.setPen(QPen(Qt::red, 1, Qt::DashDotLine, Qt::FlatCap,                         Qt::MiterJoin));     painter.setBrush(Qt::yellow);     painter.drawPath(rectPath);     // Draw Ellipse     QPainterPath ellipsePath;     ellipsePath.addEllipse(QPoint(200, 120), 50, 20);     painter.setPen(QPen(QColor(79, 106, 25), 5, Qt::SolidLine,                         Qt::FlatCap, Qt::MiterJoin));     painter.setBrush(QColor(122, 163, 39));     painter.drawPath(ellipsePath);     painter.end(); }

 Main.cpp

1 2 3 4 5 6 7 8 9 10 11 12 13 14

#include "MainWindow.h" #include <QApplication> int main(int argc, char *argv[]) {     QApplication a(argc, argv);     MainWindow w;     w.resize(640, 480);     w.show();     return a.exec(); }

编译运行

另存为svg文件