尝试在pyqt5中的鼠标事件之间切换

Question

I am trying to make a gui where the user can move the image around in drag mode and switch to draw mode to draw on an image in a qgraphicsview. I have the code from examples I have found but I can't figure out how to toggle between the two mouse events. I'm also struggling with how to link the two qgraphicsview objects so that drag and zoom events are shared between the two. My code is below if anything doesnt make any sense dont hesitate to ask. Thanks in advance.

from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtCore import Qt, QPoint
from PyQt5.QtWidgets import QMainWindow, QApplication
from PyQt5.QtGui import QPixmap, QPainter, QPen
import sys

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

    def __init__(self, parent):
        super(PhotoViewer, self).__init__(parent)
        self.drawmode=0
        self._zoom = 0
        self.drawing = False
        self.lastPoint = QPoint()
        self.image=False
        self.image=QPixmap(r"image.jpg")
        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)


#drawing events that im trying to add

#    def paintEvent(self, event):
#        painter = QPainter(self)
#        painter.drawPixmap(self.rect(), self.image)
#
#    def mousePressEvent(self, event):
#        if event.button() == Qt.LeftButton:
#            self.drawing = True
#            self.lastPoint = event.pos()
#
#    def mouseMoveEvent(self, event):
#        if event.buttons() and Qt.LeftButton and self.drawing:
#            painter = QPainter(self.image)
#            painter.setPen(QPen(Qt.blue, 7, Qt.SolidLine))
#            painter.drawLine(self.lastPoint, event.pos())
#            self.lastPoint = event.pos()
#            self.update()
#
#    def mouseReleaseEvent(self, event):
#        if event.button == Qt.LeftButton:
#            self.drawing = False



class Window(QtWidgets.QWidget):
    def __init__(self):
        super(Window, self).__init__()

        self.viewer = PhotoViewer(self)
        self.viewer2 = PhotoViewer(self)
        # 'Load image' button
        self.btnLoad = QtWidgets.QToolButton(self)
        self.btnLoad.setText('Load image')
        self.btnLoad.clicked.connect(self.loadImage)
        # draw mode
        self.btndraw = QtWidgets.QToolButton(self)
        self.btndraw.setText('Draw Mode')
        self.btndraw.clicked.connect(self.drawmode)
        # 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)
        HBlayout2 = QtWidgets.QHBoxLayout()
        HBlayout2.setAlignment(QtCore.Qt.AlignLeft)
        HBlayout2.addWidget(self.viewer2)
        HBlayout2.addWidget(self.viewer)
        HBlayout = QtWidgets.QHBoxLayout()
        HBlayout.setAlignment(QtCore.Qt.AlignLeft)
        HBlayout.addWidget(self.btnLoad)
        HBlayout.addWidget(self.btnPixInfo)
        HBlayout.addWidget(self.btndraw)
        HBlayout.addWidget(self.editPixInfo)
        VBlayout.addLayout(HBlayout2)
        VBlayout.addLayout(HBlayout)

    def loadImage(self):
        self.viewer.setPhoto(QtGui.QPixmap(r'image.jpg'))
        self.viewer2.setPhoto(QtGui.QPixmap(r'image.jpg'))
        self.image=QPixmap(r"image.jpg")

    def drawmode(self):        
        self.viewer.toggleDrawMode()

    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__':

    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    window.setGeometry(500, 300, 800, 600)
    window.show()
    sys.exit(app.exec_())

Answer 1

There's a typo in def drawmode , which calls "toggleDra w Mode" instead of "toggleDra g Mode". Besides that, it's better to avoid painting on a view (unless you really need to and know what you're doing) or directly on an image while moving the mouse, and a better approach may be to add a QGraphicsPathItem on mouse press and actually paint on the image after releasing the mouse button:

def mousePressEvent(self, event):
    if (event.button() == Qt.LeftButton and not self._photo.pixmap().isNull() 
        and self.dragMode() == QtWidgets.QGraphicsView.NoDrag):
            self.drawingPath = QtGui.QPainterPath()
            self.drawingPath.moveTo(self.mapToScene(event.pos()))
            self.drawingItem = self.scene().addPath(self.drawingPath)
            self.drawingItem.setPen(QtGui.QPen(Qt.blue, 7, Qt.SolidLine))
    else:
        super(PhotoViewer, self).mousePressEvent(event)

def mouseMoveEvent(self, event):
    if event.buttons() and Qt.LeftButton and self.drawingPath:
        self.drawingPath.lineTo(self.mapToScene(event.pos()))
        self.drawingItem.setPath(self.drawingPath)
    else:
        super(PhotoViewer, self).mouseMoveEvent(event)

def mouseReleaseEvent(self, event):
    if event.button() == Qt.LeftButton and self.drawingPath:
        pm = self._photo.pixmap()
        painter = QtGui.QPainter(pm)
        painter.setPen(QPen(Qt.red, 7, Qt.SolidLine))
        painter.drawPath(self.drawingPath)
        painter.end()
        self._photo.setPixmap(pm)
        self.scene().removeItem(self.drawingItem)
        self.drawingPath = None
    else:
        super(PhotoViewer, self).mouseReleaseEvent(event)

About the "linking" of the two views, if the drag is referred to the view scrolling, just link the two relative scrollbars valueChanged with setValue on the other, and remember that whenever you want to apply a transform you have to blockSignals(True) for all 4 scrollbars, apply the same transform on both views, and then un-block signals for the scrollbars again.