如何将 QRubberBand 约束在图像/QLabel 内？

Question

我正在 pyqt5 中创建一个图像查看器，一切正常。我需要添加一个裁剪功能，用户可以在图像上绘制一个矩形，稍后将使用该矩形。

目前，它正在完美地绘制 QRubberBand，但我希望它留在图像内部，而不是像这样在图像外部绘制：

我已经尝试过这个：

if eventQMouseEvent.pos().x() < self.imageLabel.size().width() and eventQMouseEvent.pos().y() < self.imageLabel.size().height():
                
    self.currentQRubberBand.setGeometry(QRect(self.originQPoint, eventQMouseEvent.pos()).normalized())

但它有缺陷/块状并且无法按预期工作。

这是完整的工作代码，以便您可以重新创建当前的应用程序：

from PyQt5 import QtCore
from PyQt5.QtCore import Qt, QRect
from PyQt5.QtGui import QImage, QPixmap, QPalette, QPainter
from PyQt5.QtWidgets import QLabel, QSizePolicy, QScrollArea, QMessageBox, QMainWindow, QMenu, QAction, qApp, QFileDialog, QApplication, QRubberBand
import sys

class QImageViewer(QMainWindow):
    def __init__(self):
        super().__init__()

        self.scaleFactor = 0.0
        
        self.opened = False

        self.imageLabel = QLabel()
        self.imageLabel.setBackgroundRole(QPalette.Base)
        self.imageLabel.setSizePolicy(QSizePolicy.Ignored, QSizePolicy.Ignored)
        self.imageLabel.setScaledContents(True)

        self.scrollArea = QScrollArea()
        self.scrollArea.setBackgroundRole(QPalette.Dark)
        self.scrollArea.setWidget(self.imageLabel)
        self.scrollArea.setVisible(False)

        self.setCentralWidget(self.scrollArea)

        self.createActions()
        self.createMenus()

        self.setWindowTitle("Image Viewer")
        self.resize(800, 600)

    def open(self):
        options = QFileDialog.Options()
        # fileName = QFileDialog.getOpenFileName(self, "Open File", QDir.currentPath())
        fileName, _ = QFileDialog.getOpenFileName(self, 'QFileDialog.getOpenFileName()', '',
                                                  'Images (*.png *.jpeg *.jpg *.bmp *.gif)', options=options)
        if fileName:
            image = QImage(fileName)
            if image.isNull():
                QMessageBox.information(self, "Image Viewer", "Cannot load %s." % fileName)
                return
            
            self.opened = True
            
            self.imageLabel.setPixmap(QPixmap.fromImage(image))
            self.scaleFactor = 1.0

            self.scrollArea.setVisible(True)
            self.fitToWindowAct.setEnabled(True)
            self.updateActions()

            if not self.fitToWindowAct.isChecked():
                self.imageLabel.adjustSize()

    def zoomIn(self):
        self.scaleImage(1.25)

    def zoomOut(self):
        self.scaleImage(0.8)

    def normalSize(self):
        self.imageLabel.adjustSize()
        self.scaleFactor = 1.0

    def fitToWindow(self):
        fitToWindow = self.fitToWindowAct.isChecked()
        self.scrollArea.setWidgetResizable(fitToWindow)
        if not fitToWindow:
            self.normalSize()

        self.updateActions()

    def createActions(self):
        self.openAct = QAction("&Open...", self, shortcut="Ctrl+O", triggered=self.open)
        self.exitAct = QAction("E&xit", self, shortcut="Ctrl+Q", triggered=self.close)
        self.zoomInAct = QAction("Zoom &In (25%)", self, shortcut="Ctrl++", enabled=False, triggered=self.zoomIn)
        self.zoomOutAct = QAction("Zoom &Out (25%)", self, shortcut="Ctrl+-", enabled=False, triggered=self.zoomOut)
        self.normalSizeAct = QAction("&Normal Size", self, shortcut="Ctrl+S", enabled=False, triggered=self.normalSize)
        self.fitToWindowAct = QAction("&Fit to Window", self, enabled=False, checkable=True, shortcut="Ctrl+F",
                                      triggered=self.fitToWindow)

    def createMenus(self):
        self.fileMenu = QMenu("&File", self)
        self.fileMenu.addAction(self.openAct)
        self.fileMenu.addSeparator()
        self.fileMenu.addAction(self.exitAct)

        self.viewMenu = QMenu("&View", self)
        self.viewMenu.addAction(self.zoomInAct)
        self.viewMenu.addAction(self.zoomOutAct)
        self.viewMenu.addAction(self.normalSizeAct)
        self.viewMenu.addSeparator()
        self.viewMenu.addAction(self.fitToWindowAct)

        self.menuBar().addMenu(self.fileMenu)
        self.menuBar().addMenu(self.viewMenu)

    def updateActions(self):
        self.zoomInAct.setEnabled(not self.fitToWindowAct.isChecked())
        self.zoomOutAct.setEnabled(not self.fitToWindowAct.isChecked())
        self.normalSizeAct.setEnabled(not self.fitToWindowAct.isChecked())

    def scaleImage(self, factor):
        self.scaleFactor *= factor
        self.imageLabel.resize(self.scaleFactor * self.imageLabel.pixmap().size())

        self.adjustScrollBar(self.scrollArea.horizontalScrollBar(), factor)
        self.adjustScrollBar(self.scrollArea.verticalScrollBar(), factor)

        self.zoomInAct.setEnabled(self.scaleFactor < 3.0)
        self.zoomOutAct.setEnabled(self.scaleFactor > 0.333)

    def adjustScrollBar(self, scrollBar, factor):
        scrollBar.setValue(int(factor * scrollBar.value()
                               + ((factor - 1) * scrollBar.pageStep() / 2)))
    
    def mousePressEvent (self, eventQMouseEvent):
        if self.opened:
            self.originQPoint = eventQMouseEvent.pos()
            self.currentQRubberBand = QRubberBand(QRubberBand.Rectangle, self)
            self.currentQRubberBand.setGeometry(QRect(self.originQPoint, QtCore.QSize()))
            self.currentQRubberBand.show()

    def mouseMoveEvent (self, eventQMouseEvent):
        if self.opened: 
            self.currentQRubberBand.setGeometry(QRect(self.originQPoint, eventQMouseEvent.pos()).normalized())
            
    def mouseReleaseEvent (self, eventQMouseEvent):
        if self.opened:
            self.currentQRubberBand.hide()
            currentQRect = self.currentQRubberBand.geometry()
            self.currentQRubberBand.deleteLater()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    imageViewer = QImageViewer()
    imageViewer.show()
    sys.exit(app.exec_()) 

我找到了这个答案，但它是用C++编写的，我什么都不懂。

Answer 1

这就是答案，我将选择的矩形与图像的矩形相交：

def mouseReleaseEvent (self, eventQMouseEvent):
    if self.opened:
        currentQRect = self.currentQRubberBand.geometry()
        self.currentQRubberBand.setGeometry(currentQRect.intersected(self.imageLabel.geometry()))