qt编写一段程序，实现导入图片，可在图片上选择是否添加水印

以下是一个使用Qt编写的简单程序，可以导入图片并在图片上添加水印。

首先，在Qt Creator中创建一个新的Qt Widgets Application项目。在主窗口上添加一个QLabel和一个QPushButton组件，用于显示图像和选择导入图像的按钮。代码如下：

//mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QLabel>
#include <QPushButton>

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private slots:
    void openImage();

private:
    QLabel *imageLabel;
    QPushButton *openImageButton;
    QPixmap currentImage;
};

#endif // MAINWINDOW_H

//mainwindow.cpp
#include "mainwindow.h"
#include <QFileDialog>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    imageLabel = new QLabel(this);
    imageLabel->setScaledContents(true);
    imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
    imageLabel->setAlignment(Qt::AlignCenter);
    setCentralWidget(imageLabel);

    openImageButton = new QPushButton("Open Image", this);
    connect(openImageButton, &QPushButton::clicked, this, &MainWindow::openImage);
    statusBar()->addWidget(openImageButton);
}

MainWindow::~MainWindow()
{
}

void MainWindow::openImage()
{
    QString fileName = QFileDialog::getOpenFileName(this, tr("Open Image"), "", tr("Images (*.png *.xpm *.jpg)"));
    if (!fileName.isEmpty()) {
        QPixmap newImage(fileName);
        if (newImage.isNull()) {
            QMessageBox::warning(this, tr("Error"), tr("Cannot load %1.").arg(fileName));
            return;
        }
        currentImage = newImage;
        imageLabel->setPixmap(currentImage);
    }
}

然后，我们添加一个QCheckBox组件，用于选择是否添加水印。我们还将添加一个QPainter和QLineEdit组件，以便用户可以在图像上输入文本作为水印。代码如下：

//mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QLabel>
#include <QPushButton>
#include <QCheckBox>
#include <QPainter>
#include <QLineEdit>

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private slots:
    void openImage();
    void addWatermark(bool checked);

private:
    QLabel *imageLabel;
    QPushButton *openImageButton;
    QCheckBox *watermarkCheckBox;
    QLineEdit *watermarkLineEdit;
    QPixmap currentImage;
};

#endif // MAINWINDOW_H

//mainwindow.cpp
#include "mainwindow.h"
#include <QFileDialog>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    imageLabel = new QLabel(this);
    imageLabel->setScaledContents(true);
    imageLabel->setSizePolicy(QSizePolicy::Ignored, QSizePolicy::Ignored);
    imageLabel->setAlignment(Qt::AlignCenter);
    setCentralWidget(imageLabel);

    openImageButton = new QPushButton("Open Image", this);
    connect(openImageButton, &QPushButton::clicked, this, &MainWindow::openImage);
    statusBar()->addWidget(openImageButton);

    watermarkCheckBox = new QCheckBox("Add Watermark", this);
    connect(watermarkCheckBox, &QCheckBox::toggled, this, &MainWindow::addWatermark);
    statusBar()->addWidget(watermarkCheckBox);

    watermarkLineEdit = new QLineEdit(this);
    statusBar()->addWidget(watermarkLineEdit);
}

MainWindow::~MainWindow()
{
}

void MainWindow::openImage()
{
    QString fileName = QFileDialog::getOpenFileName(this, tr("Open Image"), "", tr("Images (*.png *.xpm *.jpg)"));
    if (!fileName.isEmpty()) {
        QPixmap newImage(fileName);
        if (newImage.isNull()) {
            QMessageBox::warning(this, tr("Error"), tr("Cannot load %1.").arg(fileName));
            return;
        }
        currentImage = newImage;
        imageLabel->setPixmap(currentImage);
    }
}

void MainWindow::addWatermark(bool checked)
{
    if (checked) {
        QPainter painter(&currentImage);
        QColor watermarkColor = QColor(Qt::red);
        QFont watermarkFont = QFont("Arial", 30);
        painter.setFont(watermarkFont);
        painter.setPen(watermarkColor);
        painter.drawText(currentImage.width() - watermarkLineEdit->text().length() * 30, currentImage.height() - 30, watermarkLineEdit->text());
        imageLabel->setPixmap(currentImage);
    } else {
        imageLabel->setPixmap(currentImage);
    }
}

在此示例中，我们将水印添加到图像的右下角。当用户单击复选框时，程序将调用addWatermark()函数，该函数使用QPainter在图像上绘制文本。

这是一个简单的演示，可以帮助你入门Qt图像处理。