如何将图像添加到 QGraphicsScene 以便可以在其上定位矩形项目？

问题描述

我有一个 python 代码，可以在 QGraphicsScene 上添加多个矩形。

from PyQt5 import QtCore,QtGui,QtWidgets

class GraphicsScene(QtWidgets.QGraphicsScene):
    def __init__(self,parent=None):
        super(GraphicsScene,self).__init__(QtCore.QRectF(-500,-500,1000,1000),parent)
        self._start = QtCore.QPointF()
        self._current_rect_item = None

    def mousepressEvent(self,event):
        if self.itemAt(event.scenePos(),QtGui.QTransform()) is None:
            self._current_rect_item = QtWidgets.QGraphicsRectItem()
            self._current_rect_item.setBrush(QtCore.Qt.red)
            self._current_rect_item.setFlag(QtWidgets.QGraphicsItem.ItemIsMovable,True)
            self.addItem(self._current_rect_item)
            self._start = event.scenePos()
            r = QtCore.QRectF(self._start,self._start)
            self._current_rect_item.setRect(r)
        super(GraphicsScene,self).mousepressEvent(event)

    def mouseMoveEvent(self,event):
        if self._current_rect_item is not None:
            r = QtCore.QRectF(self._start,event.scenePos()).normalized()
            self._current_rect_item.setRect(r)
        super(GraphicsScene,self).mouseMoveEvent(event)

    def mouseReleaseEvent(self,event):
        self._current_rect_item = None
        super(GraphicsScene,self).mouseReleaseEvent(event)


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self,parent=None):
        super(MainWindow,self).__init__(parent)
        scene =GraphicsScene(self)
        view = QtWidgets.QGraphicsView(scene)
        self.setCentralWidget(view)


if __name__ == '__main__':
    import sys

    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.resize(640,480)
    w.show()
    sys.exit(app.exec_())

我的问题是如何在 QGraphicsScene（的背景）中添加图像，以便矩形覆盖在该图像上？

解决方法

有几个选项：

• setBackgroundBrush():

  brush = QtGui.QBrush(QtGui.QPixmap("/path/of/image.png"))
  scene.setBackgroundBrush(brush)
  

• 覆盖 drawBackground()：

  class GraphicsScene(QtWidgets.QGraphicsScene):
      def __init__(self,parent=None):
          super(GraphicsScene,self).__init__(QtCore.QRectF(-500,-500,1000,1000),parent)
          self._start = QtCore.QPointF()
          self._current_rect_item = None
  
      def drawBackground(self,painter,rect):
          pixmap = QtGui.QPixmap("/path/of/image.png")
          painter.drawPixmap(QtCore.QPointF(0,0),pixmap)