c++ - 如何在Qt中的特定坐标上显示图像？

Question

我在 Qt 中有这个对话框窗口类:

class Board : public QDialog
{
    Q_OBJECT

public:
    explicit Board(QWidget *parent = 0);
    ~Board();

private:
    Ui::Board *ui;

    void mousePressEvent(QMouseEvent *mouseEvent);
};

我想在函数 mousePressEvent 中根据用户给定的坐标显示 png 图像，每次用户单击对话框窗口中的某处时都会调用该函数。所以我需要像 displayImage("path/to/image.png", coordX, coordY); 这样的东西。我该怎么做？

新代码:

class Board : public QDialog
{
public:
    Board(QWidget *parent = 0) : 
    QDialog(parent),
    ui(new Ui::Board),
    view(&scene) 
{ 
    // Set background image
    /**************/
    ui->setupUi(this);

    QPixmap pix("path/background.png");
    ui->label_board->setPixmap(pix);

    /**************/
    / Set layout for displaying other images on the background
    QVBoxLayout *layout = new QVBoxLayout(this);
    layout->addWidget(&view);
    //or set the layout and the view in the designer if using Qt Creator
}

protected:
virtual void mousePressEvent(QMouseEvent *mouseEvent) override
{
    QGraphicsPixmapItem *item = new QGraphicsPixmapItem(QPixmap("path/to/image.png"));
    scene.addItem(item);
    item->setPos(coordX, coordY);
}

private:
    Ui::Board *ui;
    QGraphicsScene scene;
    QGraphicsView view;
};

label_board 是使用 Qt Designer 设置到某个位置的 500x500 标签。

Answer 1

您将需要使用 QGraphicsView ( docs ) 和 QGraphicsScene ( docs ):

class Board : public QDialog
{
public:
    Board(QWidget *parent = 0) : 
        QDialog(parent),
        ui(new Ui::Board),
        view(&scene) 
    { 
        QVBoxLayout *layout = new QVBoxLayout(this);
        layout->addWidget(&view);
        //or set the layout and the view in the designer if using Qt Creator

        //EDIT: add background like this first
        QGraphicsPixmapItem *background = QGraphicsPixmapItem(QPixmap("path/to/background.png"));
        scene.addItem(background);
        background.setPos(0, 0); //position it to cover all the scene so at 0,0 which is the origin point
        background.setScale(2.0); //scale the image to the scene rectangle to fill it
        background.setZValue(-0.1); //to ensure it is always at the back
    }

protected:
    virtual void mousePressEvent(QMouseEvent *mouseEvent) override
    {
        QGraphicsPixmapItem *item = new QGraphicsPixmapItem(QPixmap("path/to/image.png"));
        scene.addItem(item);
        item->setPos(coordX, coordY);
    }

private:
    Ui::Board *ui;
    QGraphicsScene scene;
    QGraphicsView view;
};

差不多就这些了。另请注意，该位置是项目(图像)左上角的位置。如果您想将其居中，则需要根据项目(图像)的比例调整位置。