pyqt5 QGraphicsView内缩放显示的图像

from PyQt5.QtWidgets import (QApplication, QGraphicsView, QGraphicsScene, QGraphicsItem, QGraphicsPixmapItem)
from PyQt5.QtCore import (QPointF, QPoint, QLineF, QLine, QRectF, QRect, Qt)
from PyQt5.QtGui import (QBrush, QPen, QPixmap, QPicture, QImage)
import math


class ImageView(QGraphicsView):
    def __init__(self):
        super(ImageView, self).__init__()
        self.scene = QGraphicsScene()
        self.lena = QPixmap(r"C:\Users\cpz\Pictures\temp\4E373925CBFB476dB6F3DD0A523410B7.jpg")
        self.item = QGraphicsPixmapItem(self.lena)  # 创建像素图元
        self.scene.addItem(self.item)
        self.setScene(self.scene)

    def wheelEvent(self, event):
        self.scaleView(math.pow(2.0, -event.angleDelta().y() / 240.0))

    def scaleView(self, scaleFactor):
        factor = self.transform().scale(scaleFactor, scaleFactor).mapRect(QRectF(0, 0, 1, 1)).width()

        if factor < 0.07 or factor > 100:
            return

        self.scale(scaleFactor, scaleFactor)


if __name__ == "__main__":
    import sys

    app = QApplication(sys.argv)

    view = ImageView()
    view.show()

    sys.exit(app.exec_())