QT制作一个位图画图板程序

佚名 6年前 (2019-05-05) 随笔 2059人围观抢沙发百度已收录

本文学习如何创建一个Qt绘制程序，用户将能够通过使用不同的尺寸和画笔的颜色来表达他们的创造力。

主要功能：保存画板内容为图片、清除画板内容、设置画板大小、设置画笔颜色

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新建基于QMainWindow的应用程序，设置MainWindow.ui

代码如下:

MainWindow.h

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#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

#include <QPainter>
#include <QMouseEvent>
#include <QFileDialog>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public :
     explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

     virtual void mousePressEvent(QMouseEvent *event);
     virtual void mouseMoveEvent(QMouseEvent *event);
     virtual void mouseReleaseEvent(QMouseEvent *event);
     virtual void paintEvent(QPaintEvent *event);
     virtual void resizeEvent(QResizeEvent *event);

private slots:
     void on_action_2px_triggered();
     void on_action_5px_triggered();
     void on_action_10px_triggered();
     void on_action_Black_triggered();
     void on_action_White_triggered();
     void on_action_Red_triggered();
     void on_action_Green_triggered();
     void on_action_Blue_triggered();
     void on_action_Save_triggered();
     void on_action_Clear_triggered();

private :
    Ui::MainWindow *ui;
    QImage          image;
     bool             drawing;
    QPoint          lastPoint;
     int              brushSize;
    QColor          brushColor;
};

#endif // MAINWINDOW_H

MainWindow.cpp

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#include "MainWindow.h"
#include "ui_MainWindow.h"
#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui( new Ui::MainWindow)
{
    ui->setupUi( this );

     //  create a QImage object, which acts as the canvas
    image = QImage( this ->size(), QImage::Format_RGB32);
    image.fill(Qt::white);

    QImage tux;
     //tux.load(qApp->applicationDirPath() + "/tux.png");
    tux.load( "://tux.png" );
    QPainter painter(&image);
    painter.drawImage(QPoint( 100 , 100 ), tux);

    drawing = false ;
    brushColor = Qt::black;
    brushSize = 2 ;

}

MainWindow::~MainWindow()
{
     delete ui;
}

void MainWindow::mousePressEvent(QMouseEvent *event)
{
     if (event->button() == Qt::LeftButton)
    {
        drawing = true ;
        lastPoint = event->pos();
    }

}

void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
     if ((event->buttons() & Qt::LeftButton) && drawing)
    {
        QPainter painter(&image);
        painter.setPen(QPen(brushColor, brushSize, Qt::SolidLine,
                            Qt::RoundCap, Qt::RoundJoin));
        painter.drawLine(lastPoint, event->pos());
        lastPoint = event->pos();
         this ->update();
    }

}

void MainWindow::mouseReleaseEvent(QMouseEvent *event)
{
     if (event->button() == Qt::LeftButton)
    {
        drawing = false ;
    }

}

void MainWindow::paintEvent(QPaintEvent *event)
{
    QPainter canvasPainter( this );
    canvasPainter.drawImage( this ->rect(), image, image.rect());
}

void MainWindow::resizeEvent(QResizeEvent *event)
{
    QImage newImage(event->size(), QImage::Format_RGB32);
    newImage.fill(qRgb( 255 , 255 , 255 ));
    QPainter painter(&newImage);
    painter.drawImage(QPoint( 0 , 0 ), image);
    image = newImage;

}

void MainWindow::on_action_2px_triggered()
{
    brushSize = 2 ;
}

void MainWindow::on_action_5px_triggered()
{
    brushSize = 5 ;
}

void MainWindow::on_action_10px_triggered()
{
    brushSize = 10 ;
}

void MainWindow::on_action_Black_triggered()
{
    brushColor = Qt::black;
}

void MainWindow::on_action_White_triggered()
{
    brushColor = Qt::white;
}

void MainWindow::on_action_Red_triggered()
{
    brushColor = Qt::red;
}

void MainWindow::on_action_Green_triggered()
{
    brushColor = Qt::green;
}

void MainWindow::on_action_Blue_triggered()
{
    brushColor = Qt::blue;
}

void MainWindow::on_action_Save_triggered()
{
    QString filePath = QFileDialog::getSaveFileName( this , "Save Image" ,
                                                     "" , "PNG (*.png);;JPEG (*.jpg *.jpeg);;All files (*.*)" );
     if (filePath == "" )
         return ;
    image.save(filePath);
}

void MainWindow::on_action_Clear_triggered()
{
    image.fill(Qt::white);
     this ->update();
}

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，自由绘制吧！