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 
 

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#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 
 

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#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 
 

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#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

Qt使用QPainter绘制矢量图并保存为svg文件

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