ubuntu系统下，使用qt creater,使图片输出成灰度图、降低分辨率的图片的main.cpp和mainwindow.cpp的例程,以及对应的.pro文件

以下是一个简单的例程，可以将图像转换为灰度图，并降低分辨率。需要在.pro文件中添加QT += widgets和QT += gui。

main.cpp

#include <QApplication>
#include "mainwindow.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QLabel>
#include <QImage>
#include <QSpinBox>
#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QPushButton>

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private slots:
    void openImage();
    void convertToGray();
    void reduceResolution();

private:
    QLabel *imageLabel;
    QImage image;
    QSpinBox *spinBox;
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include <QFileDialog>
#include <QMessageBox>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    imageLabel = new QLabel;
    imageLabel->setBackgroundRole(QPalette::Base);
    imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
    imageLabel->setScaledContents(true);

    QWidget *centralWidget = new QWidget(this);
    setCentralWidget(centralWidget);

    QVBoxLayout *mainLayout = new QVBoxLayout(centralWidget);

    QHBoxLayout *buttonLayout = new QHBoxLayout;
    QPushButton *openButton = new QPushButton(tr("Open"), this);
    QPushButton *grayButton = new QPushButton(tr("Convert to Gray"), this);
    QPushButton *reduceButton = new QPushButton(tr("Reduce Resolution"), this);
    spinBox = new QSpinBox(this);
    spinBox->setRange(1, 10);
    spinBox->setValue(1);

    buttonLayout->addWidget(openButton);
    buttonLayout->addWidget(grayButton);
    buttonLayout->addWidget(reduceButton);
    buttonLayout->addWidget(spinBox);

    mainLayout->addWidget(imageLabel);
    mainLayout->addLayout(buttonLayout);

    connect(openButton, SIGNAL(clicked()), this, SLOT(openImage()));
    connect(grayButton, SIGNAL(clicked()), this, SLOT(convertToGray()));
    connect(reduceButton, SIGNAL(clicked()), this, SLOT(reduceResolution()));
}

MainWindow::~MainWindow()
{

}

void MainWindow::openImage()
{
    QString fileName = QFileDialog::getOpenFileName(this, tr("Open Image"), ".", tr("Image Files (*.png *.jpg *.bmp)"));
    if (fileName.isEmpty())
        return;
    image.load(fileName);

    if (image.isNull())
    {
        QMessageBox::information(this, tr("Error"), tr("Cannot load %1.").arg(fileName));
        return;
    }

    imageLabel->setPixmap(QPixmap::fromImage(image));
}

void MainWindow::convertToGray()
{
    if (image.isNull())
        return;
    image = image.convertToFormat(QImage::Format_Grayscale8);
    imageLabel->setPixmap(QPixmap::fromImage(image));
}

void MainWindow::reduceResolution()
{
    if (image.isNull())
        return;
    int factor = spinBox->value();
    image = image.scaled(image.width() / factor, image.height() / factor);
    imageLabel->setPixmap(QPixmap::fromImage(image));
}

.pro文件

QT += widgets gui

TARGET = imageConverter
TEMPLATE = app

SOURCES += main.cpp \
    mainwindow.cpp

HEADERS += mainwindow.h

这个例程中，使用了Qt的几个基本控件，如QLabel、QSpinBox、QPushButton等，并且利用QImage类进行图像处理。openImage()函数用于打开图片，convertToGray()函数将图片转换为灰度图，reduceResolution()函数将图片降低分辨率。