Python 使控件鼠标在QGraphicsView中缩放

我有一个

QGraphicsView

，可以显示图像、放大和缩小。代码如下：

class MyQGraphicsView(QtGui.QGraphicsView):

    def __init__ (self, parent=None):
        super(MyQGraphicsView, self).__init__ (parent)

    def wheelEvent(self, event):
     # Zoom Factor
        zoomInFactor = 1.25
        zoomOutFactor = 1 / zoomInFactor

    # Set Anchors
        self.setTransformationAnchor(QtGui.QGraphicsView.NoAnchor)
        self.setResizeAnchor(QtGui.QGraphicsView.NoAnchor)

    # Save the scene pos
        oldPos = self.mapToScene(event.pos())

    # Zoom
        if event.delta() > 0:
            zoomFactor = zoomInFactor
        else:
            zoomFactor = zoomOutFactor
        self.scale(zoomFactor, zoomFactor)

    # Get the new position
        newPos = self.mapToScene(event.pos())

    # Move scene to old position
        delta = newPos - oldPos
        self.translate(delta.x(), delta.y())

我想做的是限制放大或缩小。图像大小按如下方式缩放

qgraphicsview

大小：

        scene = QtGui.QGraphicsScene()
        pixmap = QtGui.QPixmap('pic.jpeg')
        w = self.graphicsView.width()
        h = self.graphicsView.height()
        scene.addPixmap(pixmap.scaled(QtCore.QSize(w,h)))
        self.graphicsView.setScene(scene)

如您所见，图像大小相等

qgraphicsview

size。在这个位置，我不希望用户缩小图像。仅当用户放大图像时，才可以进行缩小，直到图像大小等于

qgraphicsview

size。这不是我控制的。你能给我提个建议吗