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Cómo habilitar Panorámica y Zoom en un QGraphicsView

Solución:

Esto no es demasiado difícil de hacer utilizando las capacidades integradas de QGraphicsView.

La secuencia de comandos de demostración a continuación tiene una panorámica con el botón izquierdo y un zoom de rueda (incluido el anclaje a la posición actual del cursor). los fitInView El método se ha vuelto a implementar porque la versión incorporada agrega un margen fijo extraño que no se puede eliminar.

Versión PyQt4:

from PyQt4 import QtCore, QtGui

class PhotoViewer(QtGui.QGraphicsView):
    photoClicked = QtCore.pyqtSignal(QtCore.QPoint)

    def __init__(self, parent):
        super(PhotoViewer, self).__init__(parent)
        self._zoom = 0
        self._empty = True
        self._scene = QtGui.QGraphicsScene(self)
        self._photo = QtGui.QGraphicsPixmapItem()
        self._scene.addItem(self._photo)
        self.setScene(self._scene)
        self.setTransformationAnchor(QtGui.QGraphicsView.AnchorUnderMouse)
        self.setResizeAnchor(QtGui.QGraphicsView.AnchorUnderMouse)
        self.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        self.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        self.setBackgroundBrush(QtGui.QBrush(QtGui.QColor(30, 30, 30)))
        self.setFrameShape(QtGui.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(QtGui.QGraphicsView.ScrollHandDrag)
            self._photo.setPixmap(pixmap)
        else:
            self._empty = True
            self.setDragMode(QtGui.QGraphicsView.NoDrag)
            self._photo.setPixmap(QtGui.QPixmap())
        self.fitInView()

    def wheelEvent(self, event):
        if self.hasPhoto():
            if event.delta() > 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

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

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


class Window(QtGui.QWidget):
    def __init__(self):
        super(Window, self).__init__()
        self.viewer = PhotoViewer(self)
        # 'Load image' button
        self.btnLoad = QtGui.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 = QtGui.QToolButton(self)
        self.btnPixInfo.setText('Enter pixel info mode')
        self.btnPixInfo.clicked.connect(self.pixInfo)
        self.editPixInfo = QtGui.QLineEdit(self)
        self.editPixInfo.setReadOnly(True)
        self.viewer.photoClicked.connect(self.photoClicked)
        # Arrange layout
        VBlayout = QtGui.QVBoxLayout(self)
        VBlayout.addWidget(self.viewer)
        HBlayout = QtGui.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('image.jpg'))

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

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


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

Versión PyQt5:

from PyQt5 import QtCore, QtGui, QtWidgets

class PhotoViewer(QtWidgets.QGraphicsView):
    photoClicked = QtCore.pyqtSignal(QtCore.QPoint)

    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

    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)


class Window(QtWidgets.QWidget):
    def __init__(self):
        super(Window, self).__init__()
        self.viewer = PhotoViewer(self)
        # '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)
        VBlayout.addWidget(self.viewer)
        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('image.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_())

Es posible abrir archivos TIFF de hasta varios gigabytes con la biblioteca PIL (almohada) ordinaria. No es tan fácil, pero funciona.

Puede ver el ejemplo aquí, segundo ejemplo después de negrita EDITAR string podría abrir, mover y hacer zoom en archivos TIFF.

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