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‎README.md‎

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# PyQt5基础教程(持续更新中。。。)
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* p37_大图片放大缩小 [源码下载](p37_大图片放大缩小) [博文地址](https://xugaoxiang.com/2022/12/06/pyqt5-37-image-zoom/)
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* p36_`QLabel` 滚动条 [源码下载](p36_QLabel滚动条) [博文地址](https://xugaoxiang.com/2022/12/04/pyqt5-36-make-label-scrollable/)
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* p35_`QGraphicsView` 显示图片 [源码下载](p35_QGraphicsView显示图片) [博文地址](https://xugaoxiang.com/2022/12/01/pyqt5-35-qgraphicsview/)

‎p37_大图片放大缩小/main.py‎

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import os.path
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import sys
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from PyQt5.QtCore import Qt, QRectF, QPoint, QPointF, pyqtSignal, QEvent, QSize
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from PyQt5.QtGui import QImage, QPixmap, QPainterPath, QMouseEvent, QPainter, QPen
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from PyQt5.QtWidgets import QGraphicsView, QGraphicsScene, QFileDialog, QSizePolicy
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from PyQt5.QtWidgets import QApplication
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class QtImageViewer(QGraphicsView):
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# 定义使用到的鼠标操作信号
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leftMouseButtonPressed = pyqtSignal(float, float)
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leftMouseButtonReleased = pyqtSignal(float, float)
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middleMouseButtonPressed = pyqtSignal(float, float)
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middleMouseButtonReleased = pyqtSignal(float, float)
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rightMouseButtonPressed = pyqtSignal(float, float)
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rightMouseButtonReleased = pyqtSignal(float, float)
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leftMouseButtonDoubleClicked = pyqtSignal(float, float)
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rightMouseButtonDoubleClicked = pyqtSignal(float, float)
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viewChanged = pyqtSignal()
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mousePositionOnImageChanged = pyqtSignal(QPoint)
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roiSelected = pyqtSignal(int)
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def __init__(self):
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QGraphicsView.__init__(self)
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self.scene = QGraphicsScene()
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self.setScene(self.scene)
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# 显示的图片
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self._image = None
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self.aspectRatioMode = Qt.AspectRatioMode.KeepAspectRatio
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# 默认没有滚动条
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self.setHorizontalScrollBarPolicy(Qt.ScrollBarPolicy.ScrollBarAlwaysOff)
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self.setVerticalScrollBarPolicy(Qt.ScrollBarPolicy.ScrollBarAlwaysOff)
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# 左键区域放大
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self.regionZoomButton = Qt.MouseButton.LeftButton
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# 右键缩小
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self.zoomOutButton = Qt.MouseButton.RightButton
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# 中键拖动
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self.panButton = Qt.MouseButton.MiddleButton
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# 放大或缩小的因子
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self.wheelZoomFactor = 1.25
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self.zoomStack = []
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# Flags for active zooming/panning.
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self._isZooming = False
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self._isPanning = False
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self._pixelPosition = QPoint()
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self._scenePosition = QPointF()
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self.ROIs = []
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self.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Expanding)
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def hasImage(self):
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return self._image is not None
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def setImage(self, image):
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# 同时支持 QPixmap 和 QImage
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if type(image) is QPixmap:
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pixmap = image
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elif type(image) is QImage:
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pixmap = QPixmap.fromImage(image)
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else:
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raise RuntimeError("ImageViewer.setImage: Argument must be a QImage, QPixmap.")
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if self.hasImage():
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self._image.setPixmap(pixmap)
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else:
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self._image = self.scene.addPixmap(pixmap)
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self.setSceneRect(QRectF(pixmap.rect())) # Set scene size to image size.
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self.updateViewer()
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def open(self, filepath=None):
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# 不带参数，默认打开文件选择器选择文件
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if filepath is None:
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filepath, dummy = QFileDialog.getOpenFileName(self, "Open image file.")
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if len(filepath) and os.path.isfile(filepath):
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image = QImage(filepath)
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self.setImage(image)
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def updateViewer(self):
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if not self.hasImage():
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return
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if len(self.zoomStack):
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self.fitInView(self.zoomStack[-1], self.aspectRatioMode)
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else:
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self.fitInView(self.sceneRect(), self.aspectRatioMode)
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def clearZoom(self):
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if len(self.zoomStack) > 0:
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self.zoomStack = []
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self.updateViewer()
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self.viewChanged.emit()
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def resizeEvent(self, event):
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# 事件响应
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self.updateViewer()
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def mousePressEvent(self, event):
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dummyModifiers = Qt.KeyboardModifier(Qt.KeyboardModifier.ShiftModifier | Qt.KeyboardModifier.ControlModifier
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| Qt.KeyboardModifier.AltModifier | Qt.KeyboardModifier.MetaModifier)
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if event.modifiers() == dummyModifiers:
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QGraphicsView.mousePressEvent(self, event)
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event.accept()
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return
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if (self.regionZoomButton is not None) and (event.button() == self.regionZoomButton):
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self._pixelPosition = event.pos()
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self.setDragMode(QGraphicsView.DragMode.RubberBandDrag)
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QGraphicsView.mousePressEvent(self, event)
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event.accept()
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self._isZooming = True
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return
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if (self.zoomOutButton is not None) and (event.button() == self.zoomOutButton):
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if len(self.zoomStack):
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self.zoomStack.pop()
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self.updateViewer()
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self.viewChanged.emit()
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event.accept()
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return
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if (self.panButton is not None) and (event.button() == self.panButton):
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self._pixelPosition = event.pos() # store pixel position
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self.setDragMode(QGraphicsView.DragMode.ScrollHandDrag)
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if self.panButton == Qt.MouseButton.LeftButton:
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QGraphicsView.mousePressEvent(self, event)
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else:
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self.viewport().setCursor(Qt.CursorShape.ClosedHandCursor)
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dummyModifiers = Qt.KeyboardModifier(Qt.KeyboardModifier.ShiftModifier
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| Qt.KeyboardModifier.ControlModifier
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| Qt.KeyboardModifier.AltModifier
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| Qt.KeyboardModifier.MetaModifier)
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dummyEvent = QMouseEvent(QEvent.Type.MouseButtonPress, QPointF(event.pos()), Qt.MouseButton.LeftButton,
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event.buttons(), dummyModifiers)
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self.mousePressEvent(dummyEvent)
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sceneViewport = self.mapToScene(self.viewport().rect()).boundingRect().intersected(self.sceneRect())
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self._scenePosition = sceneViewport.topLeft()
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event.accept()
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self._isPanning = True
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return
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scenePos = self.mapToScene(event.pos())
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if event.button() == Qt.MouseButton.LeftButton:
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self.leftMouseButtonPressed.emit(scenePos.x(), scenePos.y())
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elif event.button() == Qt.MouseButton.MiddleButton:
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self.middleMouseButtonPressed.emit(scenePos.x(), scenePos.y())
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elif event.button() == Qt.MouseButton.RightButton:
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self.rightMouseButtonPressed.emit(scenePos.x(), scenePos.y())
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QGraphicsView.mousePressEvent(self, event)
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def mouseReleaseEvent(self, event):
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dummyModifiers = Qt.KeyboardModifier(Qt.KeyboardModifier.ShiftModifier | Qt.KeyboardModifier.ControlModifier
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| Qt.KeyboardModifier.AltModifier | Qt.KeyboardModifier.MetaModifier)
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if event.modifiers() == dummyModifiers:
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QGraphicsView.mouseReleaseEvent(self, event)
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event.accept()
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return
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if (self.regionZoomButton is not None) and (event.button() == self.regionZoomButton):
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QGraphicsView.mouseReleaseEvent(self, event)
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zoomRect = self.scene.selectionArea().boundingRect().intersected(self.sceneRect())
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self.scene.setSelectionArea(QPainterPath())
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self.setDragMode(QGraphicsView.DragMode.NoDrag)
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zoomPixelWidth = abs(event.pos().x() - self._pixelPosition.x())
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zoomPixelHeight = abs(event.pos().y() - self._pixelPosition.y())
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if zoomPixelWidth > 3 and zoomPixelHeight > 3:
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if zoomRect.isValid() and (zoomRect != self.sceneRect()):
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self.zoomStack.append(zoomRect)
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self.updateViewer()
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self.viewChanged.emit()
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event.accept()
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self._isZooming = False
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return
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if (self.panButton is not None) and (event.button() == self.panButton):
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if self.panButton == Qt.MouseButton.LeftButton:
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QGraphicsView.mouseReleaseEvent(self, event)
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else:
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self.viewport().setCursor(Qt.CursorShape.ArrowCursor)
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dummyModifiers = Qt.KeyboardModifier(Qt.KeyboardModifier.ShiftModifier
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| Qt.KeyboardModifier.ControlModifier
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| Qt.KeyboardModifier.AltModifier
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| Qt.KeyboardModifier.MetaModifier)
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dummyEvent = QMouseEvent(QEvent.Type.MouseButtonRelease, QPointF(event.pos()),
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Qt.MouseButton.LeftButton, event.buttons(), dummyModifiers)
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self.mouseReleaseEvent(dummyEvent)
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self.setDragMode(QGraphicsView.DragMode.NoDrag)
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if len(self.zoomStack) > 0:
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sceneViewport = self.mapToScene(self.viewport().rect()).boundingRect().intersected(self.sceneRect())
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delta = sceneViewport.topLeft() - self._scenePosition
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self.zoomStack[-1].translate(delta)
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self.zoomStack[-1] = self.zoomStack[-1].intersected(self.sceneRect())
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self.viewChanged.emit()
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event.accept()
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self._isPanning = False
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return
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scenePos = self.mapToScene(event.pos())
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if event.button() == Qt.MouseButton.LeftButton:
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self.leftMouseButtonReleased.emit(scenePos.x(), scenePos.y())
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elif event.button() == Qt.MouseButton.MiddleButton:
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self.middleMouseButtonReleased.emit(scenePos.x(), scenePos.y())
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elif event.button() == Qt.MouseButton.RightButton:
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self.rightMouseButtonReleased.emit(scenePos.x(), scenePos.y())
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QGraphicsView.mouseReleaseEvent(self, event)
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def mouseDoubleClickEvent(self, event):
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if (self.zoomOutButton is not None) and (event.button() == self.zoomOutButton):
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self.clearZoom()
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event.accept()
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return
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scenePos = self.mapToScene(event.pos())
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if event.button() == Qt.MouseButton.LeftButton:
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self.leftMouseButtonDoubleClicked.emit(scenePos.x(), scenePos.y())
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elif event.button() == Qt.MouseButton.RightButton:
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self.rightMouseButtonDoubleClicked.emit(scenePos.x(), scenePos.y())
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QGraphicsView.mouseDoubleClickEvent(self, event)
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def wheelEvent(self, event):
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if self.wheelZoomFactor is not None:
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if self.wheelZoomFactor == 1:
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return
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if event.angleDelta().y() < 0:
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# zoom in
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if len(self.zoomStack) == 0:
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self.zoomStack.append(self.sceneRect())
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elif len(self.zoomStack) > 1:
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del self.zoomStack[:-1]
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zoomRect = self.zoomStack[-1]
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center = zoomRect.center()
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zoomRect.setWidth(zoomRect.width() / self.wheelZoomFactor)
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zoomRect.setHeight(zoomRect.height() / self.wheelZoomFactor)
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zoomRect.moveCenter(center)
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self.zoomStack[-1] = zoomRect.intersected(self.sceneRect())
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self.updateViewer()
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self.viewChanged.emit()
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else:
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if len(self.zoomStack) == 0:
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return
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if len(self.zoomStack) > 1:
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del self.zoomStack[:-1]
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zoomRect = self.zoomStack[-1]
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center = zoomRect.center()
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zoomRect.setWidth(zoomRect.width() * self.wheelZoomFactor)
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zoomRect.setHeight(zoomRect.height() * self.wheelZoomFactor)
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zoomRect.moveCenter(center)
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self.zoomStack[-1] = zoomRect.intersected(self.sceneRect())
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if self.zoomStack[-1] == self.sceneRect():
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self.zoomStack = []
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self.updateViewer()
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self.viewChanged.emit()
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event.accept()
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return
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QGraphicsView.wheelEvent(self, event)
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def mouseMoveEvent(self, event):
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if self._isPanning:
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QGraphicsView.mouseMoveEvent(self, event)
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if len(self.zoomStack) > 0:
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sceneViewport = self.mapToScene(self.viewport().rect()).boundingRect().intersected(self.sceneRect())
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delta = sceneViewport.topLeft() - self._scenePosition
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self._scenePosition = sceneViewport.topLeft()
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self.zoomStack[-1].translate(delta)
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self.zoomStack[-1] = self.zoomStack[-1].intersected(self.sceneRect())
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self.updateViewer()
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self.viewChanged.emit()
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scenePos = self.mapToScene(event.pos())
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if self.sceneRect().contains(scenePos):
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x = int(round(scenePos.x() - 0.5))
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y = int(round(scenePos.y() - 0.5))
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imagePos = QPoint(x, y)
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else:
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imagePos = QPoint(-1, -1)
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self.mousePositionOnImageChanged.emit(imagePos)
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QGraphicsView.mouseMoveEvent(self, event)
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def enterEvent(self, event):
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self.setCursor(Qt.CursorShape.CrossCursor)
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def leaveEvent(self, event):
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self.setCursor(Qt.CursorShape.ArrowCursor)
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if __name__ == '__main__':
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app = QApplication(sys.argv)
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viewer = QtImageViewer()
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# viewer.open(filepath='test.jpg')
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viewer.open()
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viewer.show()
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sys.exit(app.exec())

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