Question

如何在以下示例中将QGraphicsItem中绘制的像素图添加到QGraphicsScene中？

#!/usr/bin/env python

from PyQt5.QtCore import QRectF, Qt
from PyQt5.QtGui import QPixmap
from PyQt5.QtWidgets import QApplication, QGraphicsItem, QGraphicsView, QGraphicsScene, QMainWindow

class TicTacToe(QGraphicsItem):
    def __init__(self, helper):
        super(TicTacToe, self).__init__()

        self.mypixmap = QPixmap("exit.png")

    def paint(self, painter, option, widget):
        painter.setOpacity(1)
        painter.drawPixmap(0,0, 300, 300, self.mypixmap)


    def boundingRect(self):
        return QRectF(0,0,300,300)


class MyGraphicsView(QGraphicsView):
    def __init__(self):
        super(MyGraphicsView, self).__init__()
        scene = QGraphicsScene(self)

        self.tic_tac_toe = TicTacToe(self)

        scene.addItem(self.tic_tac_toe)

        self.setScene(scene)

        self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOn)
        self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOn)


class Example(QMainWindow):    
    def __init__(self):
        super(Example, self).__init__()

        self.y = MyGraphicsView()
        self.setCentralWidget(self.y)

if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    w = Example()
    w.show()
    sys.exit(app.exec_())

Answer 1

试一试：

拖放图片，放大图片 - ＆gt; Qt.Key_Right，缩小图像＆lt; - Qt.Key_Left。

from PyQt5.QtCore    import (QLineF, QPointF, QRectF, 
                             pyqtSignal, QStandardPaths, Qt)
from PyQt5.QtGui     import (QIcon, QBrush, QColor, QPainter, QPixmap)
from PyQt5.QtWidgets import (QAction, QMainWindow, QApplication, 
                             QGraphicsObject,
                             QGraphicsView, QGraphicsScene, QGraphicsItem,
                             QGridLayout, QVBoxLayout, QHBoxLayout, 
                             QFileDialog, QLabel, QLineEdit, QPushButton)
from PyQt5.QtOpenGL  import QGLFormat 

class MyGraphicsView(QGraphicsView):
    backgroundColor = QColor(28, 31, 34)     # Background color
    def __init__(self):
        super(MyGraphicsView, self).__init__()

        self.resize(800, 600)
        self.setBackgroundBrush(self.backgroundColor)
        self.setCacheMode(self.CacheBackground)
        self.setRenderHints(
            QPainter.Antialiasing | QPainter.TextAntialiasing | QPainter.SmoothPixmapTransform)
        if QGLFormat.hasOpenGL():
            self.setRenderHint(QPainter.HighQualityAntialiasing)
        self.setViewportUpdateMode(self.SmartViewportUpdate)
        self._scene = QGraphicsScene(-400, -300, 800, 600, self)
        self.setScene(self._scene)            
        self._itemImage = None

    def keyReleaseEvent(self, event):
        """ Button processing event """
        self._scaleImage(event)
        super(MyGraphicsView, self).keyReleaseEvent(event)

    def closeEvent(self, event):
        """ Clear all items in the scene when the window is `closed` """
        self._scene.clear()
        self._itemImage = None
        super(MyGraphicsView, self).closeEvent(event)

    def _scaleImage(self, event):
        """ Image zoom operation """
        if not self._itemImage:
            return
        scale = self._itemImage.scale()
        if event.key() == Qt.Key_Right:             
            # Enlarge Image -> Qt.Key_Right 
            if scale >= 0.91:
                return
            self._itemImage.setScale(scale + 0.1)
        elif event.key() == Qt.Key_Left:            
            # Reduce image <- Qt.Key_Left
            if scale <= 0.11:
                return
            self._itemImage.setScale(scale - 0.1)


    def loadImage(self):
        path, _ = QFileDialog.getOpenFileName(
            self, 'Please select an image', 
            QStandardPaths.writableLocation(QStandardPaths.DesktopLocation), 
            'Image(*.jpg *.png)')
        if not path:
            return
        if self._itemImage:
            # Delete previous item
            self._scene.removeItem(self._itemImage)
            del self._itemImage
        self._itemImage = self._scene.addPixmap(QPixmap(path))
        self._itemImage.setFlag(QGraphicsItem.ItemIsMovable)
        self._itemImage.setScale(0.1)         # Default load factor

        size = self._itemImage.pixmap().size()
        # Adjust the image in the middle
        self._itemImage.setPos(
            -size.width() * self._itemImage.scale() / 2,
            -size.height() * self._itemImage.scale() / 2
        )        


if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)

    w   = MyGraphicsView()
    w.show()
    ww = QPushButton('Select a file', clicked=w.loadImage)
    ww.show()    

    sys.exit(app.exec_())

如何将QGraphicsItem中绘制的像素图添加到QGraphicsScene？

1 个答案: