Qt使用QPainter绘制矢量图并保存为svg文件 - 我来乔23

时间:2024-02-23 18:09:01

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(
00this->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(
2040), "Hello Qt");
    
// Draw Line
    painter.drawLine(QPoint(5070), QPoint(100100));
    
// Draw Rectangle
    painter.setBrush(Qt::BDiagPattern);
    painter.drawRect(QRect(
401208030));
    
// Draw Ellipse
    QPen ellipsePen;
    ellipsePen.setColor(Qt::red);
    ellipsePen.setStyle(Qt::DashDotLine);
    painter.setPen(ellipsePen);
    painter.drawEllipse(QPoint(
80200), 5020);
    
// Draw Rectangle
    QPainterPath rectPath;
    rectPath.addRect(QRect(
1503010050));
    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(
200120), 5020);
    painter.setPen(QPen(QColor(
7910625), 5, Qt::SolidLine,
                        Qt::FlatCap, Qt::MiterJoin));
    painter.setBrush(QColor(
12216339));
    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(
640480);
    w.show();

    
return a.exec();
}

编译运行

另存为svg文件