Qt 使用QGraphicsPixmapItem、QGraphicsScene、QMatrix 的QGraphicsView的显示，缩放

.h

    QGraphicsScene *scene;
    QGraphicsPixmapItem *theFrame;
    QMatrix matrix;

.cpp

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
　　 // 初始化
    scene = new QGraphicsScene(this);
    theFrame = new QGraphicsPixmapItem();
    theFrame->setFlag(QGraphicsPixmapItem::ItemIsSelectable, false);
    theFrame->setFlag(QGraphicsPixmapItem::ItemIsMovable, false);
    theFrame->setFlag(QGraphicsPixmapItem::ItemSendsGeometryChanges);

    scene->addItem(theFrame);

    scene->setSceneRect(0,0,4096,2160);//设置 scene 尺寸

    matrix.scale(0.1, 0.1); //缩放比例
    ui->graphicsView->setMatrix(matrix);
    ui->graphicsView->scale(1,-1);
    ui->graphicsView->setScene(scene);
    ui->graphicsView->show();
}

刷新图像

theFrame->setPixmap(Pixmap);