同步两个QGraphicsView与不同的图像

Question

我想并排显示两张图像，这样当我缩放或平移一张图像时，另一张图像也会随之跟随。我当前的方法是在解析鼠标事件后发出 viewUpdated 事件。该事件包含 viewportTransformation 并用于更新其他视图中的transform。这种方法适用于缩放部分，但平移不起作用。

下面的代码基于此答案中提供的qt5版本：https://stackoverflow.com/a/35514531/185475

from PyQt5 import QtCore, QtGui, QtWidgets

# Code from https://stackoverflow.com/a/35514531
class PhotoViewer(QtWidgets.QGraphicsView):
    photoClicked = QtCore.pyqtSignal(QtCore.QPoint)
    viewUpdated = QtCore.pyqtSignal(QtGui.QTransform)

    def __init__(self, parent):
        super(PhotoViewer, self).__init__(parent)
        self._zoom = 0
        self._empty = True
        self._scene = QtWidgets.QGraphicsScene(self)
        self._photo = QtWidgets.QGraphicsPixmapItem()
        self._scene.addItem(self._photo)
        self.setScene(self._scene)
        self.setTransformationAnchor(QtWidgets.QGraphicsView.AnchorUnderMouse)
        self.setResizeAnchor(QtWidgets.QGraphicsView.AnchorUnderMouse)
        self.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        self.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        self.setBackgroundBrush(QtGui.QBrush(QtGui.QColor(30, 30, 30)))
        self.setFrameShape(QtWidgets.QFrame.NoFrame)

    def hasPhoto(self):
        return not self._empty

    def fitInView(self, scale=True):
        rect = QtCore.QRectF(self._photo.pixmap().rect())
        if not rect.isNull():
            self.setSceneRect(rect)
            if self.hasPhoto():
                unity = self.transform().mapRect(QtCore.QRectF(0, 0, 1, 1))
                self.scale(1 / unity.width(), 1 / unity.height())
                viewrect = self.viewport().rect()
                scenerect = self.transform().mapRect(rect)
                factor = min(viewrect.width() / scenerect.width(),
                             viewrect.height() / scenerect.height())
                self.scale(factor, factor)
            self._zoom = 0

    def setPhoto(self, pixmap=None):
        self._zoom = 0
        if pixmap and not pixmap.isNull():
            self._empty = False
            self.setDragMode(QtWidgets.QGraphicsView.ScrollHandDrag)
            self._photo.setPixmap(pixmap)
        else:
            self._empty = True
            self.setDragMode(QtWidgets.QGraphicsView.NoDrag)
            self._photo.setPixmap(QtGui.QPixmap())
        self.fitInView()

    def wheelEvent(self, event):
        if self.hasPhoto():
            if event.angleDelta().y() > 0:
                factor = 1.25
                self._zoom += 1
            else:
                factor = 0.8
                self._zoom -= 1
            if self._zoom > 0:
                self.scale(factor, factor)
            elif self._zoom == 0:
                self.fitInView()
            else:
                self._zoom = 0
        self.viewUpdated.emit(self.viewportTransform())

    def toggleDragMode(self):
        if self.dragMode() == QtWidgets.QGraphicsView.ScrollHandDrag:
            self.setDragMode(QtWidgets.QGraphicsView.NoDrag)
        elif not self._photo.pixmap().isNull():
            self.setDragMode(QtWidgets.QGraphicsView.ScrollHandDrag)

    def mousePressEvent(self, event):
        if self._photo.isUnderMouse():
            self.photoClicked.emit(self.mapToScene(event.pos()).toPoint())
        super(PhotoViewer, self).mousePressEvent(event)
        self.viewUpdated.emit(self.viewportTransform())

    def set_transform(self, transform):
        self.setTransform(transform)


class Window(QtWidgets.QWidget):
    def __init__(self):
        super(Window, self).__init__()
        self.viewer = PhotoViewer(self)
        self.viewerSecondImage = PhotoViewer(self)
        self.viewer.viewUpdated.connect(self.viewerSecondImage.set_transform)
        self.viewerSecondImage.viewUpdated.connect(self.viewer.set_transform)
        # 'Load image' button
        self.btnLoad = QtWidgets.QToolButton(self)
        self.btnLoad.setText('Load image')
        self.btnLoad.clicked.connect(self.loadImage)
        # Button to change from drag/pan to getting pixel info
        self.btnPixInfo = QtWidgets.QToolButton(self)
        self.btnPixInfo.setText('Enter pixel info mode')
        self.btnPixInfo.clicked.connect(self.pixInfo)
        self.editPixInfo = QtWidgets.QLineEdit(self)
        self.editPixInfo.setReadOnly(True)
        self.viewer.photoClicked.connect(self.photoClicked)
        # Arrange layout
        VBlayout = QtWidgets.QVBoxLayout(self)
        HBlayoutImageViewers = QtWidgets.QHBoxLayout()
        HBlayoutImageViewers.addWidget(self.viewer)
        HBlayoutImageViewers.addWidget(self.viewerSecondImage)
        VBlayout.addLayout(HBlayoutImageViewers)
        HBlayout = QtWidgets.QHBoxLayout()
        HBlayout.setAlignment(QtCore.Qt.AlignLeft)
        HBlayout.addWidget(self.btnLoad)
        HBlayout.addWidget(self.btnPixInfo)
        HBlayout.addWidget(self.editPixInfo)
        VBlayout.addLayout(HBlayout)

    def loadImage(self):
        self.viewer.setPhoto(QtGui.QPixmap('input/490px-Dostojka_adype.jpg'))
        self.viewerSecondImage.setPhoto(QtGui.QPixmap('input/490px-Dostojka_adype.jpg'))

    def pixInfo(self):
        self.viewer.toggleDragMode()

    def photoClicked(self, pos):
        if self.viewer.dragMode()  == QtWidgets.QGraphicsView.NoDrag:
            self.editPixInfo.setText('%d, %d' % (pos.x(), pos.y()))



if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    window.setGeometry(500, 300, 800, 600)
    window.show()
    sys.exit(app.exec_())

Answer 1

只需要同步两个QGraphicsViews的滚动条值即可，

def bindScrollBars(scrollBar1, scrollBar2):

    # syncronizing scrollbars syncrnonously somehow breaks zooming and doesn't work
    # scrollBar1.valueChanged.connect(lambda value: scrollBar2.setValue(value))
    # scrollBar2.valueChanged.connect(lambda value: scrollBar1.setValue(value))

    # syncronizing scrollbars asyncronously works ok
    scrollBar1.valueChanged.connect(lambda _: QtCore.QTimer.singleShot(0, lambda: scrollBar2.setValue(scrollBar1.value())))
    scrollBar2.valueChanged.connect(lambda _: QtCore.QTimer.singleShot(0, lambda: scrollBar1.setValue(scrollBar2.value())))
    
class Window(QtWidgets.QWidget):
    def __init__(self):
        ...
        bindScrollBars(self.viewer.horizontalScrollBar(), self.viewerSecondImage.horizontalScrollBar())
        bindScrollBars(self.viewer.verticalScrollBar(), self.viewerSecondImage.verticalScrollBar())

另外wheelEvent也可以简化

    def wheelEvent(self, event):
        if self.hasPhoto():
            factor = 1.25
            if event.angleDelta().y() > 0:
                self.scale(factor, factor)
            else:
                self.scale(1/factor, 1/factor)
        self.viewUpdated.emit(self.transform())