python - 如何在 QGraphicsView 中启用平移和缩放

Question

我正在使用 python 和 Qt Designer 来实现加载 tiff 图像并在某些鼠标事件(滚轮 - 缩放、按下滚轮 - 平移)上启用平移和缩放。

我正在研究一些可以处理图像等的选项和类，到目前为止我发现了:

QGraphicsScene, QImage, QGraphicsView

我有三个类(class)(只是测试)

1. ViewerDemo 有 QGraphicsView 元素:

       """description of class"""
       # Form implementation generated from reading ui file 'GraphicsViewdemo.ui'
       try:
       _fromUtf8 = QtCore.QString.fromUtf8
       except AttributeError:
           def _fromUtf8(s):
               return s
           class Ui_Dialog(object):
               def setupUi(self, Dialog):
                   Dialog.setObjectName(("Dialog"))
                   Dialog.resize(500, 500)
               self.graphicsView = QtGui.QGraphicsView(Dialog)
               self.graphicsView.setGeometry(QtCore.QRect(0, 0, 500, 500))
               self.graphicsView.setObjectName(("graphicsView"))
               self.retranslateUi(Dialog)
               QtCore.QMetaObject.connectSlotsByName(Dialog)
           def retranslateUi(self, Dialog):
               Dialog.setWindowTitle(QtGui.QApplication.translate("Dialog", "Dialog", None,
   QtGui.QApplication.UnicodeUTF8))
   

2. MyForm 类，也就是QDialog，我在其中调用类ViewerDemo，加载Image，并将图片放入 QGraphicsView

       import sys
       from ViewerDemo import *
       from PyQt4 import QtGui
       class MyForm(QtGui.QDialog):
           def __init__(self, url, parent=None):
               QtGui.QWidget.__init__(self, parent)
   
   
               self.ui = Ui_Dialog()
               self.ui.setupUi(self)
               self.scene = QtGui.QGraphicsScene(self)
              self.image = QtGui.QImage(url)
               pixmap= QtGui.QPixmap.fromImage(self.image)
               item=QtGui.QGraphicsPixmapItem(pixmap)
               self.scene.addItem(item)
               self.ui.graphicsView.setScene(self.scene)
               self.scale = 1
               QtCore.QObject.connect(self.scene, QtCore.SIGNAL('mousePressEvent()'),self.mousePressEvent)
   
       def mousePressEvent(self, event):
           print ('PRESSED : ',event.pos())
   

(3) 就是应用程序正在执行的地方:

    from PyQt4 import QtGui, QtCore
    import sys
    from MyForm import MyForm
    if __name__ == "__main__":
        app = QtGui.QApplication(sys.argv)
        url = "D:/probaTiff"
        myapp = MyForm(url)
        myapp.show()
        sys.exit(app.exec_())

我找到了如何通过单击鼠标(左键和滚轮单击)来打印像素坐标(例如，我需要它来获取图片 WGS84 坐标系中的坐标)。

我更需要的是如何缩放图片(滚轮或双击，随便什么)和平移图片(按住鼠标左键单击或按住滚轮)。

或者，是否有一些更好的 Qt 类来执行此操作，以及一些更好的方法 你能帮帮我吗？

这就是我到目前为止的代码

Answer 1

使用 QGraphicsView 的内置功能，这并不难。

下面的演示脚本具有左键平移和滚轮缩放(包括锚定到当前光标位置)。 fitInView 方法已重新实现，因为内置版本添加了一个无法删除的奇怪的固定边距。

PyQt4版本:

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_())

PyQt5 版本:

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_())