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(,,,);//设置 scene 尺寸

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

刷新图像

theFrame->setPixmap(Pixmap);